Applied Human Nutrition.pdf

7/23/2019 Applied Human Nutrition.pdf

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Applied Human Nutrition ANU 306 (2+0)

What is Nutrition? According to Robinson nutrition is the science of foods, nutrients, and other

substances ; therein; their action, interaction, and balance in relationship to health, and diseases; the

processes by which the organism ingests, digests, absorbs, transports, and utilizes nutrients and

disposes of their end products.

What are the frontiers of nutrition science? The frontiers of science of nutrition include the followings:

1. Growth

2. Development

3. Maintenance

4. Repair

5. Immuno-competence

6. Ageing

7.

Mental-well being

8. Prevention of degenerative diseases and cancer.

Relation of nutrition to human health

1. Nutrition and immunity: nutrition is an important determinant of immunological status; and that

under nutrition could impair immune-competence and increase susceptibility and vulnerability

to infections. Immune system could be affected by nutritional deficiencies and under nutrition

usually implies deficiencies of more than one nutrient. These can impair the immune system.

Under nutrition can affect both humoral and cellular immunity. T-cell, B-cell and macrophage

can all be affected. Several nutrients such as proteins, lipids, and micronutrients such as zinc,

iron, vitamin A, vitamin B6and copper have been shown to affect immune system.

The lymphoid tissues which play a dominant role in immunity are highly vulnerable to under nutrition.

Thymus shrinks in malnutrition and the cortico-medullary differentiation is lost; mature fully

differentiated T-lymphocytes are reduced in number and their maturation is impaired. There is also a

distortion in the relative proportions of helper (inducer) and suppressor T-cells. Many cells of the

immune system including T-cells have to depend for their functions on metabolic pathways which need

various nutrients such as carotenoids, zinc, iron, copper, and vitamin B6 and other micronutrients as

cofactors. Short supply of these nutrients impairs the functioning of the cells.

The process of phagocytosis a major defense mechanism is also impaired in the under nutrition. The

role of vitamin C, zinc, and other nutrients in phagocytosis are well established. The production of

several cytokines-including interleukins and interferon is decreased in under nutrition.

Low birth weight infants born to under nutrition mothers have sub-optimal immune responses and are

therefore susceptible to infections. There is a high neonatal mortality in low birth weight infants.

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Role of bioactive phytochemicals in foods

Foods contain disease preventing and health promoting bioactive phytochemicals. Some bioactive

phytochemicals present in foods are as follows:

------------------------------------------------------------------------------------------------------------------------------------------

phenolic compounds indoles

Flavonoids anthocyanins

Isoflavonoids, isothiocyanates anthocyanins

Coumarins diterpenes

Lignins.

Bioactive phytochemicals in foods act in three ways:

1. Antioxidants

2. Detoxifying agents

3. Blocking/suppressing agents

Antioxidants

The normal functioning of cells depends on a proper balance of pro-oxidants and antioxidants. Pro-

oxidants promote the release of oxygen to provide the energy needed for cell functioning. Antioxidants

help to neutralize and counteract the deleterious free radicals. Oxidation produces free radicals

generated as a result of natural metabolic process. Free radicals could promote lipid peroxidation

impairing cell functioning. They could damage cellular proteins and DNA. They can damage cellular

proteins and DNA.

Antioxidants present in some foods help to neutralize free radicals through protective mechanisms as

oxygen quenching, chain termination, radical scavenging. Some nutrients as carotenoids , ascorbic acid,

and tocopherols act as antioxidants. They act synergistically with such other antioxidants as phenols

and flavonoids present in foods. They help to contain the deleterious effects of free radicals. Prominent

common foods possessing such antioxidants are green leafy vegetables, fruits, like amla, and guava,

palm oil and sunflower oils and spices like turmeric and cloves.

Detoxifying agents

Toxic chemicals in the environment are removed from the body by two processes. Firstly, the toxic

molecules are transferred into rapidly extractable form through a number of reactions largely mediated

through the microsomal mixed function oxidase system (MFO).

In the second phase, the toxic molecules are converted into still more extractable form by a set of

enzymes. Examples of foods which contain such detoxifying chemicals are Brussels sprout, cabbage,tomatoes, strawberries, pineapples, green peppers, and green and black tea. These foods contain

chemicals which are in the nature of indole derivatives, that act by inducing glutathione Stransferase,

a key phase 2 enzymes. Other foods such as broccoli and green onions exert similar protective effects

through induction of another key phase -2 enzymes, namely quinine reductase.

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Blocking /suppressing agents

Bioactive phytochemical in foods sequester and prevent potential toxic agents and carcinogens from

reaching the target tissues, or by suppressing their action. Garlic, for example, is known to contain allelic

sulphides which can not only induce phase -2 enzymes, but also inactivate carcinogens. Agoene , a

chemical in garlic prevent platelet aggregation . The beneficial effect of garlic in heart disease could be

attributed to these chemicals. Chemical allin contained in garlic, cloves get converted to allicin when the

garlic is crushed because of the action of enzymes in garlic.

Flavonoids present in foods have been shown to act by scavenging superoxide anion, single oxygen and

lipid peroxide radicals. Thus, quercetin , a major flavonoid has been shown to inhibit oxidation and

cytotoxicity of LDL. Flavonoids have also been shown to inhibit cytooxygenase leading to inhibition of

platelet aggregation and reduced thrombotic tendencies. Regular intake of flavonoids in their natural

form through vegetables and fruits reduce the risk of deaths from coronary heart disease and reduce

the risk of lung cancer.

Foetal undernutrition and adult chronic disease

Body tissues of the foetus have a long " elephantine memory" and nutritional injuries inflicted to them

are not forgiven or forgotten. McKeigue and coworker have reported a greater vulnerability of Indians

migrants to foreign countries to coronary heart diseases and diabetes as compared to European and

other ethnic groups. This increased susceptibility is part of syndrome X, characterized by abdominal

obesity, hyperinsulinaemia, hypertriglyceridaemia, low concentration of high density lipoprotein (HDL)

and hypertension. Increased susceptibility to syndrome X could be the result of maternal nutritional

deprivation during critical phases of fetal growth, leading to intrauterine growth retardation (IUGR).

Barker et al studied on white indigenous population of Britain and concluded the following results:

1. Mortality rates from coronary heart diseases were three times higher in men who had weighed

18 lbs or less at one year of age than in those who had weighed 27 lbs or more.

2. The prevalence of diabetes fell from 27 % in subjects who had weighed 5.5 lbs or less at birth to

6 % in those who had weighed 7.5 lbs or more.

3.

The prevalence of syndrome X fell from 30 % in men who had 5.5 lbs or less at birth to 6 % in

those who had weighed 9.5 lbs or more.

Nutrition and ageing

Nutrition plays an important role in:

1. Retarding the ageing process and in ensuring that the reduction in functional enzymes-a central

attribute of ageing-is minimized.

2. Overcoming suboptimal immune-competence largely responsible for increased vulnerability to

infection in old age

3. Improving mental function.

Retardation of ageing

The ageing process is attributed to the accumulation of somatic mutations in DNA resulting in defective

RNA unable to produce essential functional enzymes in adequate amounts. The mutations in DNA are

the result of oxidative damage caused by free radicals generated in the course of cell metabolism in the

absence of an adequate supply of key antioxidants. Bioactive chemicals in several plant foods (fruits and

vegetables) could help to dispose of free radicals and to detoxify mutagen. Nutrients like vitamin E,

carotenoids and ascorbic acid also contribute to this process.

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Improving immune-competence

Ageing is also associated with impaired immune-competence and consequent increased vulnerability to

infection related morbidity-especially respiratory diseases. The most common nutrient deficiencies

contributing to suboptimal immunity in old age are those of iron, zinc, and vitamin c; correction of these

deficiencies has been shown to improve immunity.

Improving mental function

Good nutrition contributes to the minimization of impairment of mental function in old age. Three

classes of nutrients may play a role in this regard.

1.

There are some nutrients which are the precursor of neurotransmitters. Tryptophan is the

precursor for serotonin synthesis. This is related to sleep, food intake and mood. Tyrosine is

needed for the synthesis of catecholamine neurotransmitter, namely dopamine, adrenaline, and

noradrelanine. Choline is the precursor for the synthesis of acetylcholine-the neurotransmitter

most severely impaired in senile dementia and Alzheimer's disease. This is related to memory.

2. Nutrients such as pyridoxine, vitamin C, and thiamin affect neurotransmitter because of their

roles in metabolic pathways in the synthesis of the neurotransmitter. For example pyridoxine in

the synthesis of dopamine and serotonin and vitamin C and copper in the conversion of

dopamine to noradrenaline.

3. Some nutrients like folate, vitamin B12 , riboflavin, and nicotinic acid play role in brain

metabolism

Nutrition and coronary heart disease

As is now well known, there are two processes involved in the pathogenesis of CHD, namely thrombosis

and atherosclerosis. Dietary factors modulate them.

Nutrient guidelines for prevention of heart diseases (WHO, 1990)

1. Calorie should be sufficient to maintain appropriate body weight for a given height.

2.

Cholesterol should not exceed 300 mg/day in diet.3.

Saturated fat should be less than 10 % of total calories.

4. Polyunsaturated fat should not exceed 8 % of the total calories.

5. Linoleic acid should range between 3-7 5 of calories.

6. Alpha- linolenic acid should not be less than 1 % of the calories.

7. Proteins should provide around 10-15 % of total calories.

8. Carbohydrates should contribute 55-65 % of calories, with emphasis on complex carbohydrates.

9. Sugar should be less than 10-15 % total calories.

10.Salt intake should be between 5-7 g/day.

11.

Dietary fiber should be around 40 g/day.

Weight control

Body mass index (wt in kg /ht m2) exceeding 25 could be considered overweight and above 30 obesity.

Ideal body weight must be achieved not only through dietary discipline, but also through optimal

exercise. Abdominal obesity, characterized by elevated waist/hip ratio appears to be particularly

harmful.

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Abdominal obesity

CHD and diabetes have been found to part of syndrome X in the development of which two

components are believed to be involved.

Syndrome X (Insulin Resistance Syndrome)

Insulin Resistance

HypertriglyceridaemiaHyperinsulinaemia

Low HDL levels

Hypertension

Abdominal obesity (elevated waist/hip ratio)

A waist-hip ratio exceeding 0.85 is indicative of abdominal obesity.

Feed intake

It is now known that not all saturated fats are hypercholesterolaemic; while lauric and myristic acids do

raise blood cholesterol, stearic acid and short-chain fatty acids do not. Oleic acid which is a

monounsaturated fatty acid lowers blood cholesterol almost as effectively as the essential fatty acid-linoleic acid. The rise in triglycerides (VLDL) often observed in subjects on high carbohydrate diets can be

reduced by oleic acid.

Carbohydrates

Carbohydrates and lipids are interrelated in their metabolism and hormonal action. Carbohydrates

contribute significantly to endogenous synthesis of triglycerides. Complex carbohydrates have a low

glycaemic index as compared to sugar and jiggery. Populations subsisting on diets high in complex

carbohydrates and low in fat have lower levels of total and LDL cholesterol than those subsisting on high

fat, high sugar, and high meat diets. High carbohydrates diets contribute to low HDL levels, which are

non-beneficial. Optimal levels of exercise could help to combat this.

Nutrition and cancer

Changes in dietary practices could make a major contribution towards the prevention and containment

of the cancer problem. Dietary factors could play a significant role in the initiation, promotion and

progression of cancers. High fat intakes and especially of saturated fats are considered to favor

development of rectal and breast cancers; high animal protein and red meat intake to favor the

development of prostrate, uterine and ovarian cancers and high salt /nitrate and nitrosamine in drinks

and salted foods to favor the development of stomach and esophageal cancers.

Certain dietary factors play a protective inhibitory role, such as dietary fiber with respect to colon

cancer, micronutrients such as beta-carotene, vitamin A , riboflavin, vitamin C , iron, zinc, and selenium

with respect to cancers of epithelial origin-especially those of alimentary and respiratory tract.Vegetables and fruits rich in such micronutrients are protective against such cancers of epithelial origin.

Apart from micronutrients, bioactive phytochemicals such as isothiocyanate indoles, flavones, phenols,

protease inhibitors, allilium compounds have been found to protect against several steps in

carcinogenesis. There is recent evidence that Chinese tea has a cancer-protective agent. Some phyto-

esterogens in foods such as soya products are claimed to be beneficial in hormone-related cancer,

curcumin in turmeric, Protease inhibitors in soya have also been credited with beneficial effects in

cancer.

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Some dietary factors could be pro-carcinogenic. The process of cooking foods such as grilling, broiling or

smoking could result in the formation of carcinogenic compounds. Contamination of foods with fungi

such as aflatoxin (in the case of liver cancer) or ochratooxin A (in the case of cancer of kidney and

oesophagus) can also have harmful effects on health.

Apart from the possible role of dietary factors in the causation of cancer, there are also nutrient

supplements to protect against cancer. Post-operative morbidity in cancers can be reduced by proper

nutritional support

Impact of advancing knowledge

1. Return to breast feeding as the preferred method of infant rearing.

2. Recognition of dietary fiber.

3. Reduction in the intake of red meat and cream.

4. Increase the intake of vegetables and fruits

5. Increasing the recognition of virtues of vegetarianism.

Dietary guidelines for heart disease prevention (American Heart association, 1982)

1. Eat a variety of foods.

2.

Maintain ideal weight.3. Avoid too much fat, saturated fat, and cholesterol: excess fat leads to high levels of blood fats

and cholesterol carried in lipoprotein compounds. Elevated serum levels of these fats and

cholesterol are associated with a higher risk of coronary heart disease. Reduce the dietary fat

kilocalories to no more than 30 to 35 % of the total kilocalories.

4. Eat foods with adequate starch and fiber: certain types of dietary fiber may help control chronic

bowel diseases, contribute to improved blood glucose management for persons with diabetes

mellitus, and bind dietary lipids such as cholesterol. Increase carbohydrate kilocalories to

replace reduced fat, with 50 to 55 % of the total calories coming from carbohydrates.

5.

Avoid too much sugar.

6.

Use protein in moderation, about 12 to 30 % of the diet's total calories, with less use of animal

protein, which carries more fat.7. Cholesterol: limit dietary cholesterol to 300 mg or less per day.

8. Avoid too much sodium: excessive sodium is not healthy for anyone. A reasonable limit of 2 to 3

g of sodium a day can be achieved by using salt lightly in cooking.

9. If you drink alcohol, do so in moderation: alcohol beverages tend to be high in kilocalories and

low in other nutrients. Limited food intake may accompany large alcohol intake. Heavy drinking

contributes to chronic liver disease and some neurologic disorders, as well as some throat and

neck cancers.

Dietary guidelines for cancer prevention (the committee on Diet, Nutrition, and cancer of the national

cancer Institute, 1982).

1.

Fat: reduce fat intake to 30 % of the total calories and avoid obesity.2. Dietary fiber: include fruits, vegetables and whole-grain cereals in the daily diet.

3. Preserved food: limit use of food preserved by salt-curing, smoking, or nitrite curing.

4.

Contaminated food should be avoided.

5. Alcohol: in moderation, if at all.

6. Include fruits and vegetables in daily diets.

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Carbohydrates

Functions of carbohydrates

1.

Energy: when carbohydrate is burned in the body, it renders 4 kilocalories of energy per gram.

To function properly, the body tissues require a daily dietary supply of carbohydrate providing

50 to 55 % of the total kilocalories.

Carbohydrate energy reserves: the amount of carbohydrate in the body is important for maintainingenergy reserves. For example, in an adult male about 300 g is stored in the liver and muscle tissues

as glycogen, and about 10 g is present in circulating blood sugar. This total amount of available body

glucose provides energy sufficient for only about half a day of moderate activity. Therefore,

carbohydrate foods must be ingested regularly and at moderately frequent intervals to meet the

constant energy demands of the body.

Available carbohydrate

Of the total carbohydrate ingested, three general factors affect the amount that will be available for

use and the way the body will use it:

a.

The state of the mucous membrane of the digestive tract and the time carbohydrate is held incontact with this absorbing surface affect the bioavailability of carbohydrates. Intestinal disease

of the mucosal lining or hyper-motility, which causes rapid passage of the food mass, greatly

decreases the proportion of the ingested carbohydrate that will be used by the body.

b.

Endocrine function is also important in carbohydrate bioavailability. Several hormones play

important roles in the use of carbohydrates. Among these are insulin and the several insulin

antagonists such as hormones from the pituitary gland, steroids from the adrenal gland,

glucagon from the pancreas, and epinephrine from the adrenal medulla. Imbalance among

these various regulatory agents can greatly affect the use of carbohydrate in the body.

c. Vitamins must be present in adequate amounts. Vitamins of the B-complex especially are

involved in the metabolism of carbohydrate. Thiamin, niacin, riboflavin, and others perform key

functions as coenzymes in the enzyme systems for the oxidation of carbohydrate to yield

energy.

2. Special functions of carbohydrate in body tissues:

Glycogen reserves: liver and muscle glycogen reserves provide a constant interchange with the body's

overall energy balance system and protects cells from depressed metabolic function and injury.

Protein-sparing action:carbohydrate helps to regulate protein metabolism. The presence of sufficient

carbohydrates to meet energy demands prevents the channeling of too much protein for this purpose.

This protein sparing action of carbohydrate allows a major portion of protein to be used for its basic

structural purposes of tissue building.

Anti-ketogenic effect: the amount of carbohydrate present determines how much fat will be broken

down to supply a back-up energy source, thus affecting the formation and disposal rates of ketones.

Ketones are intermediate product of fat metabolism, which normally are produced at a low level during

fat oxidation to maintain the body supply. However, in extreme conditions such as starvation or

uncontrolled diabetes in which carbohydrate is inadequate or unavailable for energy needs, excess fat is

oxidized and ketones accumulate. The result is ketoacidosis. Thus sufficient dietary carbohydrate helps

prevent a damaging excess formation of ketones.

Heart: heart action is a life-sustaining muscular exercise. Although fatty acids are the preferred regular

fuel of the heart muscle, the glycogen in cardiac muscle is an important emergency source of contractile

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energy. In damaged heart, poor glycogen stores or low carbohydrate intake may cause cardiac

symptoms or angina.

Central nervous symptoms: a constant amount of carbohydrate is necessary for the proper functioning

of the central nervous system. Brain depends on a minute-to minute supply of glucose from the blood.

Sustained and profound hypoglycemic shock may cause irreversible brain damage. In all nerve tissue,

carbohydrate is indispensible for functional integrity.

Classification of carbohydrates

There are two basic types of carbohydrates: simple and complex carbohydrates or polysaccharides.

Simple carbohydrates:

1. Monosaccharides: monosaccharides include trioses, tetroses, pentoses , hexoses and heptoses.

The three hexose sugars most important in human nutrition are glucose, fructose, and

galactose.

Physiologic and nutritional significance of monosaccharides

Source SignificancePentoses

D-Ribose formed through metabolic component element of

Process nucleic acid and coenzyme

Hexoses

D-glucose fruit juices, honey, hydrolysis of cell fuel

Starch, cane sugar, maltose and

Lactose

D-fructose fruits, juices, honey, hydrolysis changed to glucose

of sucrose from cane sugar in the liver.

D-galactose hydrolysis of lactose (milk sugar) changed to glucose

In the liver.

D-mannose hydrolysis of plant mannosans, gums component of poly-

Saccharide of albumins,

Globulins, mucoprotein,

Glycoprotein.

2. Disaccharides: Sucrose = glucose + fructose

Lactose = glucose + galactose

Maltose = glucose + glucose

Physiologic and nutritional significance of disaccharides------------------------------------------------------------------------------------------------------------------------------------------

Source Significance

Maltose starch digestion by amylase, commercial hydrolyzed to D-glucose, basic

Hydrolysis, malt and germinating cereals body fuel

Sucrose cane and beet sugar hydrolyzed to glucose and

Fructose, basic body fuel

Lactose milk hydrolyzed to glucose and

Galactose, basic body fuel

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Polysaccharides:

They are composed of many single monosaccharide units. These polysaccharides include starch,

glycogen, and dietary fiber.

Starch: it is the most significant polysaccharide in human nutrition. It yields glucose on hydrolysis or

digestion. It is made up of amylase (15 to 20 %, soluble part of starch) and amylopectin (80 to85 % , theinsoluble part of starch, forms past with hot water and thickens during cooking ). Amylase is better than

amylopectin in maintaining normal blood sugar through a slower, more even rate of digestion and

glucose absorption. When foods high in amylase starch are developed they could benefit obese persons

and those with diabetes. The cooking of starch improves the flavor and softens and ruptures these

starch cells, which facilitates enzymatic digestive processes. Starch mixtures thicken when cooked

because of the amylopectin that encases the starch granules. About 50 to 55 % of total kilocalories in

human 's diet should come from starch.

Glycogen:

It is the storage polysaccharide and has significant function in the human energy balance system. It is an

important link in energy metabolism because it helps sustain normal blood sugar levels during fasting

periods such as sleep hours and provides immediate fuel for muscle actions.

Dietary fiber:

Dietary fiber refers to the total amount of naturally occurring material in foods, mostly plants, that is not

digested. It includes cellulose, hemicelluloses, pectin, gums, mucilage and algal substances.

Summary of dietary fiber classes

Dietary fiber class Plant parts Main chain Side branches Functions

Cellulose Main cell wallconstituent

Glucose None Insoluble holdswater,laxative,

reduces elevated

colonic

intraluminal

pressure,bind

minerals.

Dietary fiber Plant parts Main chain Side branches Functions

Hemicelluloses Secretions, cell

wall material

Glucose, mannose,

xylose

Galactose and ,

arabinose

Insoluble, holds

water, increases

stool bulk, reduces

colonic pressure,binds bile acids.

Pectin Intracellular

cement material

Galaturonic acid Rhamnose, xylose,

arabinose, fucose

Soluble, binds

cholesterol, and

bile acids.

Gums Cell secretions Galactose,

galacturonic acid-

mannose,

galacturonic acid-

xylose, galactose Soluble, bind

cholesterol, and

bile acid, slows

gastric emptying ,

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rhamnose provides

fermentable

material for

colonic bacteria

with production of

VFA and gas

Mucilage Cell secretions Galactose-

mannose, glucose-mannose,

arabinose-xylose,

glacturonic acid-

rhamnose

Galactose Soluble, slows

gastric emptyingtime; fermentable

substrate for

colonic bacteria,

binds bile acids

Algal substances Algae, seaweeds Glucose, mannose,

xylose, glucuronic

acid

Galactose Soluble, slows

gastric emptying

time, fermentable

substrate, bind

bile acids.

Non carbohydrate:

lignin

Woody parts of

plants

Phenyl propane

alcohol

3-dimentional net

work

Insoluble,

antioxidants, bind

bile acids, and

metals

Physiologic effects of crude fiber in human health

1. Water absorption: fiber contributes to bulk-forming laxative effect and influence the transit time

of the food mass through the digestive tract. This accelerated passage of the food mass in turn

affects the rate of absorption of the various nutrients in the food mix.

2. Binding effect: certain fibers bind bile salts and cholesterol, preventing their absorption. Excess

dietary fiber binds minerals such as iron, zinc, and calcium.

3. Relation to colon bacteria: nun-dietary cellulose such as gums provides fermentation substances

for colon bacteria, producing volatile short chain fatty acids and gas.4. Satiety: it adds bulk to the mixed feed. High fiber foods usually take more time to eat. Both

these factors may help control the amount of food consumed and together with the increased

transit time in the body, may contribute to the management of obesity and diabetes.

Relation of dietary factors to gastrointestinal problems, cardiovascular disease, diabetes mellitus, and

colon cancer.

1. Gastrointestinal problems: water-insoluble dietary fibers such as cellulose and hemi-cellulose

affect gastrointestinal problems such as constipation. Water held by the fibers increases the

volume of the feces and softens the stool, causing the colon muscles to contract and propel the

food residue quickly. The fecal volume is also influenced by the effect of water-soluble dietaryfibers such as gums, which increase the bacterial growth and colon flora production of volatile

fatty acid. The bile acids that some dietary fibers transport to the colon may have similarly

cathartic effects. An insoluble dietary fiber prevents and treats prevention of diverticular

disease. The basic cause of diverticula is a rise in intraluminal pressure in a segment of colon. ,

usually in the sigmoid region. A high fiber diet prevents the segmental pressure rise, reducing

the incidence of symptoms from diverticular disease

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2. Cardiovascular disease:certain soluble dietary fibers, gums in foods such as oat-bran and beans

have been shown to effectively reduce high levels of serum cholesterol. In the colon, soluble

fibers are almost completely fermented to short-chain fatty acids. Then these fatty acids,

absorbed directly into the portal vein, may in turn inhibit hepatic and peripheral cholesterol

synthesis and increase LDL cholesterol clearance.

3. Diabetes mellitus: they help in the following ways:

a.

Increased insulin receptor binding.b. Delayed gastric emptying

c. Reduced intestinal transit time with subsequent nutrient absorption.

d. Slower ingestion of bulky food.

4. Colon cancer:

a.

A high-fat diet increases the level of fecal bile acids, which may promote tumor directly or

indirectly through conversion by colon bacteria to secondary bile acids that act as tumor

promoters.

b. Dietary fiber interacts to reduce tumor risk by increasing fecal volume thus reducing the

concentration of potentially carcinogenic substances in the bowl, reducing transit time through

the colon, thus reducing the contact between fecal carcinogens and the colonic mucosa, altering

colon bacterial metabolism to favor decreased carcinogen production.

Dietary fiber recommendation: at least 15 to 20 g of total dietary fiber per day from a variety of plant

sources. Indiscriminate use of bran is not justified. This can easily be achieved through generous use of

whole grains, legumes, vegetable, fruits, seeds and nuts. Indiscriminate use of bran is not justified

because too much dietary fiber can cause nutrient loss resulting from binding of iron, zinc, and calcium.

Lactose intolerance: most adults are intolerant of milk because they are deficient in lactase. Nearly all

children and infants are able to digest lactose. In lactase deficient adult, lactose accumulates in the

lumen of the small intestine after ingestion of milk because there is no mechanism for the uptake of this

disaccharide. The large osmotic effect of the unabsorbed lactose leads to an influx of fluid into the small

intestine. Hence, the clinical symptoms of lactose intolerance are abdominal distention, nausea,

cramping, pain, and a watery diarrhea. Lactose deficiency appears to be inherited as an autosomal

recessive trait and is usually first expressed in adolescence or young adulthood. Human populations that

do not consume milk in adulthood generally have a high incidence of lactase deficiency. Milk treated

with lactase is available for consumption by lactose-intolerant people.

Lipids

Fats are a group of organic substances fats, oils and maxes, and related compounds that are greasy to

the touch and not soluble in water.

Classification of lipids

1.

Simple lipids: they are neutral fats and waxes. Neutral fats are compounds of fatty acids andglycerol, in the ratio of three fatty acids to each glycerol base. Thus they are called triglycerides.

Similarly, waxes are compounds of fatty acids with straight chain alcohols. Waxes have no

importance in human nutrition.

2. Compound lipids: compound lipids are various combinations of neutral fat with other

components. Three examples of compound lipids important in human nutrition are:

phospholipids example is lecithin, glycolipids composed of fatty acids, nitrogen and

carbohydrates, found chiefly in brain tissue as cerebrosides, and lippoproteins, complexes of

various lipids with protein and transport fat in the blood.

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3. Derived lipids: fat substances may be derived from simple and compound lipids by hydrolysis or

enzymatic breakdown. Three important members of this group are fatty acids, glycerol, and

steroids that contain cholesterol.

Fatty acids:

The fatty acids of biological importance are mostly straight chain aliphatic, monocarboxylic acids with

an even number of carbon atoms and general formula CH3(CH2) n= COOH, where n varies from 2 to 22.

Depending upon the chain length they can be classified as short chain (2 to 8 carbon atoms) , medium

chain (10-14 carbon atoms), and long chain (16-24 carbon atoms) fatty acids. They are further classified

into saturated (carbons linked by single bonds), monounsaturated (two adjacent carbons joined by a

double bond) and polyunsaturated fatty acids (PUFA) with more than one double bond and chain length

16,20 and 22 carbon atoms. The numbering of carbon atoms of fatty acids can be from carboxyl group (

numbering system) , or from terminal methyl group ( W or n numbering system) of the fatty acids. The

carbon numbers for stearic acid in the two systems are as follows:

W or n numbering 1 16 17 18

H3C (CH2)14 CH2 CH2 COOH

numbering 18 3 2 1

Four groups of PUFA (n-9, n-7, n-6, and n-3) are present in the mammalian tissues. The number after n

denotes the position of the first double bond. First two series, namely n-9 and n-7 are synthesized from

palmitooleic (16:1 n-9) acid, which in turn are derived from palmitic and stearic acids respectively by

the action of 9desaturasebof liver microsomes. The other two series, namely n-6 and n-3 are derived

from linoleic (18:2, n-6) and linolenic (18:3 , n-3 ) acids with first double bond at sixth and third carbons

respectively. These two fatty acids are required for growth and development, but cannot be synthesized

by most of the animals and humans and are therefore called essential fatty acids (EFA). Long chain PUFA

are obtained from their four precursors fatty acids by the action of various liver microsomal desaturases

and elongases. The same enzyme systems are involved in the biosynthesis of all the four series of PUFA

and hence there is a competition among the substrates for these enzymes. 6

desaturase enzyme isabsent in carnivores such as animals of cat family and hence arachidonic acid is also essential for these

animals.

Saturated fatty acids Number of carbon

Formic 1

Acetic 2:0

Propionic 3:0

Butyric 4;0

Valeric 5:0

Caproic 6:0

Caprylic 8:0

Capric 10;0

Lauric 12:0

Myristic 14:0

Palmitic 16:0

Stearic 18:0

Lignoceric 20:0

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Unsaturated fatty acids

Palmitoleic 16:1(9)

Oleic 18:1(9)

Vaccenic 18:1(11)

Linoleic 18:2(9, 12)

Linolenic 18:3(9, 12, 15)

Arachidonic 20:4 (5, 8, 11, 14)Eicosapentanoic acid 20:5 (5, 8, 11, 14, and 17)

Docosahexaenoic acid 22:6 (4, 7, 10, 13, 16, and 19)

Functions of fatty acids:

Non-eccosanoid functions

Fatty acids as constituents of membrane phospholipids are involved in the homeoviscous control of

membrane bilayer and fluidity of most cells. In this capacity they may directly or indirectly affect the

properties of membrane proteins (transporters, ion channels, hormones and receptors).

Eicosanoids and their functions

Eicosanoids are the oxidation products of 20-carbon PUFA, (arachidonic and eicosapentaenoic acids)

derived from essential fatty acids by the action of enzymes cyclo-oxygenase and lipo-oxygenase

Cyclo-oxygenase products: three series of prostaglandin may be derived from three precursor fatty acids

, namely dihomo--linolenic acid, arachidonic and eicosapentaenoic acids. Prostaglandins of I-series

namely PGE1, PGD1 and PGF1 are formed from dihomo- -linolenic acid. Arachidonic acid generates

prostaglandins of 2-series ( PGE2, PGD2and PGF2) while eicosapentanoic acid generates prostaglandins

3- series ( PGE3, PGD3and PGF3). In addition, in platelates, cyclooxygenase product of arachidonic and

eicosapentaenoic acids are converted to thromboxane A2 and A3 ( TXA2 and TXA3) by the action of

thromboxane synthetase. TXA2is a potent platelet aggregator and vasoconstrictor with a short biological

half life. In the vascular endothelial cells, arachidonic acid is converted to prostacycline I2( PGI2) whichhas vasodilator and antiaggregatory effects. Therefore PGI2and its synthetic analogues are used in the

treatment of thrombotic disorders. In human platelets and endothelial cells TXA3 and PGI3 are not

formed in appreciable amounts both due to lower intake of the precursor n-3 fatty acids as well as

various metabolic constraints. However, high dietary intake levels of n-3 fatty acids can increase

eicosapentaenoic acid and docosahexaenoic acids levels in membranes and increase the production of

TXA2and PGI3.

Since, dietary fat is the only source of n-6 and n-3 fatty acids. , optimal health benefits can be derived by

maintaining a balance in the intake of these two polyunsaturated fatty acids. The n-6 and n-3 patty acids

play important role in growth and development.

Lipoxygenase products: Leukotriens : Leukocytes generate leukotriens (LT) A4and A5from arachidonic

and eicosapentaenoic acids. They act as a potent chemotactic agent involved in the migration and

aggregation of macrophages and neutrophils at the site of infection.

Essential fatty acids: fatty acids that is necessary for body metabolism and cannot be manufactured by

the body so must be supplied in the diet. The essential fatty acid is linoleic acid.

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Functions

Linoleic acid serves important functions in the body:

1. Capillary and cell membranes: linoleic acid strengthens membrane structure, helping to prevent

an increase in skin and membrane permeability. A linoleic deficiency leads to a breakdown in

skin integrity, resulting in a characteristic eczema and skin lesions. Like other fatty acid, linoleic

acid combines with cholesterol to form cholesterol esters. Fatty acids are also part of thephospholipids and lipproteins

2. Cholesterol esters: cholesterol occurs only in animal fats and tissues and not in plants. Linoleic

acid combines with cholesterol to form cholesterol esters. Fatty acids are also part of the

phospholipid and lipoprotein lipid combinations.

3. Blood clotting: linoleic acid helps prolong blood clotting time and increase fibrinolytic activity.

4.

Local hormone-bile effects: linoleic acid is a major metabolic precursor of physiologically and

pharmacologically active compounds known as prostacyclins, prostaglandins, thromboxanes and

leukotriens. They have extensive local hormone-like effects, are synthesized in the body from

arachidonic acid derived from essential linoleic acid.

Omega-3 fatty acids:

Classification and food sources of omega fatty acids:

Class fatty acid food sources

Omega-3 linolenic acid vegetable oils

Eicosapentaenoic acid (EPA) sea food, fatty fish

Docosahexaenoic acid (DHA) sea food, fatty fish

Omega-6 linoleic acid vegetable oils

Arachidonic acid animal food sources.

Omega-9 oleic acid vegetable oils (mainly olive, peanut)

Meat fats (mainly pork, beef, chicken}Functions of fat in human nutrition and health

1. Energy: a major function of fat in human nutrition is to supply a concentrated available fuel for

energy production.

2. Thermal insulation: a padding of adipose tissue surrounds vital organs such as the kidneys, and

protects them from mechanical shock or injury.

3.

Nerve impulse transmission: fat insulation surrounding myelinated nerve fibers provides both

electrical insulation and aid for the transmission of nerve impulses.

4.

Tissue structure: fat serves as a vital constituent of cell membrane structure and participates in

the transport of nutrient materials and metabolites across cell membranes. The cell membrane

is composed of a lipid matrix with receptors protein molecules dispersed throughout.5. Cell metabolism: combinations of fat and protein are important as cell constituents and

lipoprotein carriers of fat throughout the body's blood circulation to all tissues.

6. Essential precursor substances: fat supplies necessary components for the synthesis of many

materials required for metabolic functions and tissue integrity. These precursors' materials

include fatty acids and cholesterol.

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Health problems with fat

Health problems with fat focus on two main issues:

1. Too much dietary fat

2. Too much of that fat from animal food sources.

Amount of fat

Too much fat in the diet provides excessive kilocalories, more than that required for immediate energy

needs. The excess is stored as increasing adipose tissue and body fatness. The increased obesity has

been associated with diabetes, hypertension, and heart disease.

Type of fat

Excesses in the diet of saturated fat, which comes mainly from animal food sources, and of cholesterol,

which comes only from animal food sources, have been associated with increased blood lipids linked to

atherosclerosis, the underlying blood vessel disease process that contributes to heart attacks and

strokes.

Dietary fats:

Fats (triglycerides) in the diet are referred to as saturated or unsaturated fat. If there is a predominance

of unsaturated fatty acids, the fat is called unsaturated fat. If there is predominance of saturated fatty

acids, the fat is called a saturated fat. Generally, the more unsaturated a fat, the lower its melting point

and the more likely it is to be liquid at room temperature. Saturated fats tend to remain solid at room

temperature. Foods from animal sources such as meat, eggs, and milk fat contain more saturated than

unsaturated fat. Conversely, foods from plant sources such as vegetable oils contain more unsaturated

fat. The proportion of saturated and unsaturated fatty acids in a fat will vary from one food to another

and affect its physical properties.

Visible and hidden food fats

In most cases the food sources of fat are quite evident in fatty acids, these are called visible fats. They

include butter, margarine, oil, bacon, and cream. Less obvious hidden fats in foods are contained in lean

meat, egg yolks, nuts, seeds, olives, and avocardo. A large part of hidden fat comes from relatively high

consumption of meats. Even when all the fat is trimmed off a piece of meat, its lean portion still

contains 4 to 12 % hidden fat. The higher grade of meat has considerable "marbling" tiny fat deposits

within the muscle tissue.

Cholesterol

Cholesterol is not a fat itself. It is a fat-related compound by its ability to combine with fatty acids toform cholesterol esters.

Functions:

Cholesterol is a vital substance in human metabolism. It is a precursor of to all steroid hormones. A

cholesterol product in the skin, 7-dehydrocholesterol, is irradiated by the sun's ultraviolet rays to make

vitamin D hormone. it is also essential in forming bile acids, which are required for the digestion and

absorption of fats in the intestine. Cholesterol is widely distributed in all body cells, and large amounts

occur in brain and nerve tissues. It is an essential component of all cell membranes. The endogenous

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supply is synthesized mainly in the liver. If a person consumed no exogenous supply of dietary

cholesterol at all, the body would still synthesize an adequate amount for metabolic needs.

Food sources

Cholesterol occurs naturally in all animal foods and only in animal foods. Its main food sources are egg

yolks, and organ meats such as liver and kidney. Vegetable oils and their food products do not contain

cholesterol. Although the plant oils vary in their degree of saturation, none of them contain cholesterol.

Health concern

Atherosclerosis is the underlying disease process in blood vessels in which fatty deposits or plaques

containing cholesterol build up in and on the walls of arteries. This occurs as a result of elevated serum

cholesterol levels. Thus the American Heart Association recommends the intake 300 mg of cholesterol

/day. An increase in some types of dietary fiber is also recommended because these fibers bind bile

acids and helps eliminate excess cholesterol from the body. Other major risk factors associated with

development of atherosclerosis are hypertension and cigarette smoking.

Lipoproteins

The lipoproteins are highly significant in human nutrition. They are important combinations of fat and

other lipid components such as cholesterol, allowing them to travel in the blood stream.

Functions:

Because fat is insoluble in water , a means of transporting fat throughout the body in a water based

circulatory system , the blood presents a problem. The body has solved this problem through the

development of the lipoproteins, a package of fat wrapped in water soluble protein. These plasma

lipoproteins contain triglycerides, cholesterol, unesterified fatty acids, phospholipids, and traces of other

related materials such as fat-soluble vitamins and the steroid hormones. Because the densities of the

various lipoproteins vary according to their fat load, they have been separated and studied by a processof electrophoresis. The high or low density of the lipoprotein transport complex is determined by its

relative ratio of fat and protein. The higher the protein ratio , the higher the density. The higher the fats

and other related lipids such as cholesterol, the lower the density. Thus the lipoproteins are classified

according to density and by relative fat and cholesterol loads as (1) chylomicrons, formed in the

intestinal wall and carrying the large fat load from meal just consumed. (2)very-low density lipoprotein,

(VLDL) , formed from the chylomicrons in the continuing process of lipid transport and metabolism; (3)

low density lipoproteins (LDL), formed from VLDL fragments and carrying cholesterol in the cells; and

(4) high-density lipid protein (HDL), carrying cholesterol from cells to the liver for breakdown and

elimination from the body.

Proteins

All proteins , whether it is tissue protein in our bodies or food protein in our diet , is made up of

building units or compounds called amino acids. These compounds form the structural units of protein.

Out of a total of 20 or more, 10 are considered dietary essentials, indispensible to life. These amino

acids are joined in specific chain sequence to form specific proteins.

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Functions of dietary protein:

1. The primary function of dietary protein is to supply amino acids in the quantity and kind

necessary for growth and maintenance of body tissues. Thus the age and physical activity of an

individual influence amounts needed.

2. Specific physiologic roles:

a. Methionine: an essential amino acids , is a methylating agent that participates in the formation

of nonprotein cellular constituents such as choline which is a precursor of acetylcholine, one ofthe neurotransmitters. Methionine is not only the precursor of the nonessential amino acid

cystine, but also carnitine and taurine.

b. Tryptophan: it is the precursor of niacin and vasoconstrictor and neurotransmitter serotonine.

c.

Phenylalanine: it the precursor of non-essential amino acid tyrosine. Together with tyrosine,

phenylalanine leads to formation of the hormones thyroxine and epinephrine.

3. Available energy: protein also contributes to the body's overall energy metabolism. After

removal of the nitrogenous portion of the constituent amino acids, the amino acid residue may

be either glycogenic (glucogenic) , capable of being converted to glucose or ketogenic , capable

of being converted to ketones. Only leucine, phenylalanine, and tyrosine are fully ketogenic. The

remaining amino acids are glucogenic. It is estimated that on the average, 58 % of the total

dietary protein may become available as glucose according to need and is oxidized as such toyield available energy.

Functions of recently discovered amino acids

Taurine: it is one of the most abundant free amino acids in human milk. Dietary sources of taurine are

largely animal protein foods. It is virtually absent in plant foods. Taurine functions in the formation of

bile acids, regulation of heart beat, control of brain neurons, and central nervous system activity,

maintenance of membrane stability, and integrity of retinal and vision function

Carnitine: it is formed from methionine and lysine, with vitamin C, vitamin B6, niacin and iron acting as

necessary nutrient cofactors with the cell enzymes in its synthesis. the major metabolic role is

associated with the transport of long-chain fatty acids across the mitochondria membranes , thusstimulating the oxidation of these fuel substrates for metabolic energy. It forms complex esters with

many of the acyl compounds , metabolic intermediary products from fats and carbohydrates. An

accumulation of such metabolites in cells can inhibit cell enzyme functions and become toxic, creating a

carnitine deficiency. Carnitine converts many of the acyl compounds to less toxic forms and removes

them from the cell. Dietary sources of carnitine are largely limited to animal protein foods. It is absent

from plant proteins

Amino acid required in human nutrition

Essential amino acids

Eight amino acids are called essential amino acids because they are the only ones we cannot make.

Essential amino acids Semiessential amino acids nonessential amino acids

Isoleucine Arginine alanine

Leucine Histidine Asparagine

Lysine aspartic acid

Methionine Cystine (cysteine)

Phenylalanine glutamic acid

Glutamine

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Threonine glycine

Tryptophan Hydroxyproline

Valine Hydroxylysine

Proline

Serine

Tyrosine

X semi-essential because the rate of synthesis in the body is inadequate to support growth, thereforethey are essential for children.

Complete and incomplete food proteins

Complete proteins are those that contain all the essential amino acids in sufficient quantity and ratio to

meet the body's needs. These proteins are of animal origin: eggs, milk, cheese, and meat.

Incomplete protein: these proteins are those deficient in one or more of the essential amino acids.

These proteins are mostly of plant origin: grains, legumes, nuts, and seeds. In a mixed diet, however,

animal and plant proteins complement one another. Even a mixture of plant proteins may provide an

adequate balanced ratio of amino acids if planned carefully.

Types of proteins:

1. Simple proteins: simple proteins contain only amino acids or their derivatives. Some examples

include serum albumin, insulin, and the enzymes.

2. Complex proteins: complex proteins are made up of simple proteins plus some other non

protein group. Examples include:

a. Nucleoproteins: one or more proteins plus nucleic acid, such as DNA protein complex in cell

nuclei.

b. Glycoproteins and mycoproteins: protein and carbohydrate, such as mucin. , found in secretions

from mucous membranes.

c. Phosphoproteins: protein and a phosphorus containing compounds such as casein in milk.

d.

Chromoproteins: protein and pigmented group, such as hemoglobin in red blood cells.e. Lipproteins: protein and a triglyceride

f. Metalloproteins: protein and a mineral such as copper or iron such as heme, the iron binding

portion of hemoglobin.

Tissue proteins

Based on their role in body structure and metabolism.

1. Structural protein: collagen in connective tissue.

2. Contractile proteins: myosin (muscle)

3. Antibodies: Gammaglobulin.

4. Blood proteins: albumin, fibrinogen, hemoglobin.

5.

Hormones: insulin.6. Enzymes: all the enzymes.

Protein requirement:

Factors affecting requirement:

1. The rate at which protein tissue is synthesized in the body at a given time and the nature and

caloric value of the diet as a whole.

2. Nature of the diet influences the quantitative protein requirement because of the protein

sparing effect of the carbohydrate and fat energy sources contained in the diet.

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3. Timing of meals also plays a role. Allowing time intervals between eating protein feeds lowers

the competition for absorption sites and enzymes.

4. Clinical factors such as fever, disease processes , medications, traumatic injury, and the post

surgical state.

Measures of protein requirements

Two basic measures of protein requirements must be considered: quantity and quality.

Protein quantity:The US RDA standard has generally been set for adults at 0.8 g/kg of body weight. This

amount is about 56 g daily for a man weighing 79 kg and 50 g daily for a women weighing 63 kg. a total

of at least 60 and 50 g daily for a woman weighing 63 kg. a total of at least 60 to 65 g daily is needed

during pregnancy, and lactation. The requirements for infants and children vary according to age and

growth patterns.

Protein quality: the nutritive value of a protein is often expressed in terms of its chemical score. The

nutritive value of a protein is often expressed in terms of its chemical score. Using the amino acid

pattern of a high-quality protein food such as egg and giving it a value of 100, other foods are compared

according to their ratios of the essential amino acids. The essential amino acid showing the greatest

deficit limits the body's utilization of that protein and thus is termed its limiting amino acid. The

percentage of that amino acid present in the food , in comparison with the standard protein , provides

the chemical score. The three essential amino acids most often limiting in proteins are tryptophan,

lysine and methionine.

Measures to determine protein quality

1. Biological value: BV is the percentage of absorbed nitrogen retained in the body.

2. Net protein utilization (NPU) : this is the product of BV and the degree of proteins digestibility.

3. Protein efficiency ratio ( PER): this is based on the weight gain of a growing test animal divided

by its protein intake over a study period of about 10 days.

Comparative protein quality of selected foods according to chemical score , Biological value, Net

protein utilization, and protein efficiency rato

Food chemical score BV NPU PER

Egg 100 100 94 3.92

Cow's milk 95 93 82 3.09

Fish 71 76 --- 3.55

Beef 69 74 67 2.30

Unpolished rice 67 86 59 ----Peanuts 65 55 55 1.65

Oats 57 65 --- 2.19

Polished rice 57 64 57 2.18

Whole wheat 53 65 49 1.53

Corn 49 72 36 ----

Soybeans 47 73 61 2.32

Sesame seeds 42 62 53 1.77

Peas 37 64 55 1.57

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Vegetarian diets

Types of diets

Protein requirements in various vegetarian diets may be met by applying the principle of

complementary plant proteins to achieve the necessary balance amino acids.

There are four basic types of vegetarian diets:

1.

Lactoovovegetarian: one who accepts milk products and eggs and no other animal products.2. Lactovegetarian: one who accepts dairy products?

3. Pure vegetarian : one who rejects all animal protein foods and uses only plant food sources-

grains, legumes, vegetables, fruits, seeds and nuts

4. Ovovegetarians : who allows eggs as their only source of animal protein.

5. Animal vegetarians:

a.

Prescovegetarians: who permits fish as the only animal product in their diet.

b.

Pollovegetarians: who allows poultry as the only animal product in their diets.

c. Red meat abstainers: who eat any animal product except red meat but still consider

themselves vegetarians.

Does a vegetarian diet offer important nutrients?

Vegetarians can meet the recommended dietary allowances for most major nutrients without takingsupplements. However, a few key nutrients create problems if the vegetarian is not careful.

Vitamin B12: the vitamin is found only in animal products. Vegetarians are at the greatest risk for a

deficiency. A deficiency can be avoided by including fortified foods or by taking a vitamin B12.

Vitamin A : vegetarians tend to get major pro -vitamin A, carotene, than they need. This usually isnot a

problem, unless they are also taking supplements that include vitamin A. these may include as much as

10 times the RDA for vitamin A. as a fat soluble vitamin, vitamin A can build up in the body tissues and

reach toxic levels. The results could be irritability, dry skin, and hair loss. Vegetarians should be careful

to keep their vitamin A intake near the recommended amount of 800 retinol equivalents (RE) per day.

Iron: grains and legumes have iron, but much of it is poorly absorbed from the gut. Absorption can be

enhanced by including a good source of vitamin C in the same meal.

Minerals in human nutrition

Metabolic roles of minerals are as follows:

1. They are builders: calcium and phosphorus provide structural body frame work. Oxygen hungry

iron provides the core of heme in hemoglobin. Cobalt is a component of vitamin B12.

2. They are activators. The minerals are active participants in the overall metabolic proces

3.

They are regulators.

4.

They are transmitters of nerve impulses.

5.

They are controllers: ionized sodium and potassium exercise all-important control over shifts in

body fluids.

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Major minerals: elements for which the requirement is greater than 100 mg/day. They constitute 60 to

80 % of all the inorganic material in the human body.

Trace elements: those needed in much smaller amounts are called trace elements.

------------------------------------------------------------------------------------------------------------------------------------------

Major minerals trace elements Essentiality unclear

(Required intake over 100 mg/day (required intake under 100 mg/day

------------------------------------------------------------------------------------------------------------------------------------------

Calcium ( Ca ) iron ( Fe ) silicon ( Si )Phosphorus (P ) Iodine (I ) Vanadium ( V )

Magnesium (Mg ) Zinc ( Zn ) Nickel ( Ni )

Sodium ( Na ) Copper ( Cu ) Tin ( Sn )

Potassium ( K) Manganese ( Mn ) Cadmium ( Cd )

Chloride ( Cl ) Chromium ( Cr ) Arsenic ( As )

Sulfur ( S ) Cobalt ( Co ) Aluminium ( Al )

Selenium ( Se ) Boron ( B ).

Molybdenum ( Mo )

Fluorine ( Fu )

Major minerals:

Calcium

Factors increasing calcium absorption:

1. Body need: calcium absorption is increased by greater body need.

2. Plasma ion concentration: even small decreases in the concentration of ionized calcium in the

body fluids are reflected in a rise in calcium absorption. The calcium ion concentration in turn is

is mediated by an intracellular receptor protein, calmodulin, that binds calcium ions when their

concentration increases in response to a stimulus. It is in this ionized form that ionized calcium

in plasma modulates the activities of a greater variety of metabolic functions.

3. Dietary protein: a greater percentage of calcium is absorbed when the diet is high in protein.

However, this larger amount absorbed results in increased renal excretion, with a negative

calcium balance following. Thus, high protein diets in effects induce increased calciumrequirement to maintain calcium balance.

4. Dietary carbohydrates: lactose generally enhances the absorption of calcium in the ikeum,

through the action of the lactobacilli, to produce lactic acid, which lowers the pH

5.

Acidity: lower pH (increased acidity) favors solubility of calcium and consequently its absorption.

Factors decreasing calcium absorption:

1. Vitamin D deficiency: calcium cannot be absorbed normally when there is a deficiency of vitamin

D.

2. Dietary fat: excess dietary fat or poor absorption of fats result in an excess of fat in the intestine

, which inhibits calcium absorption through formation of insoluble calcium soaps. Theseinsoluble soaps are excreted, with the consequent loss of the incorporated calcium.

3. Calcium phosphorus ratio: in the diet, the optimal dietary calcium phosphorus ratio is 1.0 to

1.5 for children and women during the latter half of pregnancy and during lactation. Other

adults require a 1 : 1 dietary ratio. If either mineral is taken in excess, absorption of both is

hindered , and excretion of the lesser mineral is increased. For example, excess phosphorus in

relation to the amount of calcium in the intestine will form more calcium phosphate, which

binds the calcium and make it unavailable for absorption.

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4. Fiber and other binding agents: an excess of fiber in the diet binds calcium and hinders its

absorption. Other binding agents include oxalic acid, which combines with calcium to produce

calcium oxalate and phytic acid which forms calcium phytate and prevents its absorption. Oxalic

acid is a constituent of green leafy vegetables, but the amount of oxalate varies in these

vegetables so that some are better sources of calcium than others. Phytic acid is found in the

outer hulls of many cereal grains, especially wheat.

5. Alkalinity: calcium is insoluble in an alkaline medium and therefore is poorly absorbed.

6.

Excretion: dietary calcium taken in excess of need remains unabsorbed in the intestine and iseliminated in the feces.

Physiologic functions:

1.

Bone formation :

2.

Tooth formation.

3. Blood clotting. The calcium ions are required for cross-linking of fibrin, giving stability to the

fibrin threads.

4. Nerve transmission: calcium is required for normal transmission of nerve impulses. A current of

calcium ions triggers the flow of signals from one nerve cell to another and on to the waiting

target muscles. The calcium ions in the extracellular fluid at the neuromuscular junction cause

the neurotransmitter acetylcholine to pass through the separating membranes at the tips of the

many nerve branches and excite the muscle fiber.

5.

Muscle contraction and relaxation: each muscle fiber contains hundreds of small contractile

units called myofibrils, which are composed of the muscle protein filaments, myosin and actins.

Alongside of each myofibril is a fine system of tubes, the tubular reticulum. Calcium is firmly

bound to this reticulum. When the signal for contraction comes, the calcium is suddenly

released, ionized, and mobilized. The free calcium ions activate the chemical reaction between

myosin and actin a filament that releases a large amount of energy from ATP and brings about

contraction. The calcium are then immediately bound back on to the reticulum, causing

relaxation

6. Cell membrane permeability: ionized calcium controls the passage of fluid through cell

membranes by affecting cel wall permeability. It influences the integrity of the intercellular

cement substance.7. Enzyme activation: calcium ions are important activators of certain enzymes such as ATPase in

the release of energy for muscle contraction

Clinical problems:

1.

Tetany : a decrease in ionized serum calcium causes tetany, a state marked by severe,

intermittent spastic contractions of the muscle and muscular pain.

2. Osteoporosis: this is characterized by loss of bone mineral, occurs mostly in older persons

especially postmenopausal women.

3. Resorptive hypercalciuria.: two conditions are known to tilt the usually fine-tuned calcium

deposition -mobilization balance by the modulating hormones. When these conditions occur ,

there is excess calcium withdrawal resorption from bone and subsequent elevated calcium

excretion in the urine. One of these conditions is prolonged immobilization , such as occurs with

a full body cast after orthopedic surgery or spinal cord injury or with a body brace following a

back injury. In such cases the risk of renal stone formation is increased. A second example is the

hypercalciuria observed in astronauts.

4. Hyperparathyroidism and hypoparathyroidism : because calcium and phosphorus metabolism

are directly controlled by parathyroid hormone, conditions of the parathyroid gland that

increase or decrease the secretions of its hormone will immediately be reflected in abnormal

metabolism of these two minerals

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Calcium requirement:

Adults : 800 mg daily.

Women during pregnancy and lactation: 1200 mg daily.

Infants under 1 year of age : 400 to 600 mg

Children: 800 to 1200 mg.

Food sources:Dairy products provide the bulk of dietary calcium, eggs, green leafy vegetables, broccoli, legumes, nuts,

and whole grains.

Phosphorus

Physiologic functions

1. Bone and tooth formation.

2. General metabolic activities: its presence in every living cell reflects its vital metabolic role.

3. Absorption of glucose and glycerol: by the process of phosphorylation , Phosphorus combines

with glucose and glycerol from fat to promote the absorption of these substrates from the

intestine. Phosphorylation also promotes the renal tubular reabsorption of glucose, by which

this sugar is conserved and returned to the blood.

4.

Transport of fatty acids: by combining with fat as phospholipids , phosphorus helps provide a

vehicular form of fat.

5. Energy metabolism: phosphorus containing compounds are widespread in the cell and include

such examples as DNA, phosphhatides, and ATP.

6. Buffer system: the phosphate buffer system and phosphoric acid and phosphate contribute

additional control of acidosis and alkalosis states in the blood.

Clinical problems:

1.

Physiologic changes:a. Recovery from diabetic acidosis: increases in carbohydrate absorption and metabolism use

much phosphorus in the activation of enzymes for producing glycogen and for glycolysis, thus

causing temporary hypophosphatemia.

b. Growth needs: growing children usually have high serum phosphate levels, resulting from high

levels of growth hormone.

c. Pathologic changes: situations involving pathologic changes in serum phosphate levels include

the following:

Hypophosphatemia: low serum phosphate levels occur in intestinal diseases such as sprue and

celiac disease, which hinder phosphorus absorption or bone disease such as rickets or osteomalacia

which upset the calcium phosphorus serum ratio. The serum phosphate level is also low in primaryhyperparathyroidism because the excess quantity of parathyroid hormone secreted results in

excessive renal tubular excretion of phosphorus. Symptoms of hypophosphatemia include muscle

weakness, because the muscle cells are deprived of phosphorus essential for energy metabolism.

Hyperphosphatemia: renal insufficiency or hypoparathyroidism, causes excess accumulation of

serum phosphate. As a result, the calcium side of the calcium phosphorus serum ratio is low,

causing tetany.

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Phosphorus requirements:

During growth and pregnancy, lactation, the ideal dietary calcium is about 1.0 to 1.5 for men and

non-pregnant women; the recommended intake of phosphorus is the same as that for calcium. In

general , an adequate adult intake of phosphorus is about 800 to 1500 mg/day. The RDA standard

recommends a phosphorus allowance equal to that for calcium for all ages (800 1200 mg) except

the young infant, for whom the proportion of phosphorus is lower than for calcium ( 300 -500 mg).

Calcium /phosphorus ratio:

The dietary ratio of 1 :5 is ideal for periods of rapid growth , 1 :1.5 for normal adult functions. The

normal serum ratio for adults is 40 ( 10 mg/DL calcium x 4 mg /DL phosphorus ), and for children is

50 ( 10 mg/DL calcium x 5 mg /DL phosphorus ).

Food sources

Milk and milk products are the most significant sources of phosphorus, lean meats are good sources.

Magnesium:

Metabolic functions:

1.

Carbohydrate metabolism: ionized magnesium serves as an activator of many enzymes in the

reactions of the initial glycolytic pathway for glucose oxidation oxidative phosphorylation.

2. Protein metabolism: ionized magnesium is a coenzyme in protein synthesis in the cell

ribosomes.

3. Cell reproduction and growth: magnesium is a constituent of molecules formed in the process of

cell growth and maintenance of tissues.

4. Hormonal action: magnesium is related to cortisone in the regulation of the blood phosphorus

levels.

5. Smooth muscle action: decreased plasma ionized magnesium causes vasodilation and inhibits

smooth muscle action. Any changes in its intracellular fluid concentration produceneuromuscular irritability.

Clinical problems:

Malabsorption: in various gastrointestinal disorders, such as prolonged diarrhea or vomiting or diseases

characterized by intestinal malabsorption, excessive amounts of magnesium are lost. Rehydration must

be accompanied by adequate magnesium replacements or the resulting low serum magnesium level will

cause general neuromuscular irritability manifested by tremor, spasm, and increased startle response to

sound and touch. Avoiding a rapid re-feeding program following a period of malnutrition will prevent

serious metabolic and neurologic disturbances.

Magnesium requirements

250 to 300 mg /day

Food sources:

Magnesium is relatively widespread in nature. Its main sources include nuts, soybeans, cocoa, seafood,

whole grains, dried beans and peas.

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Sodium Metabolic functions

1. Fluid balance: ionized sodium is the major cation of the extracellular fluid and serves as the

guardian of this fluid compartment.

2. Acid-base balance: through its association with chloride and bicarbonate ions, ionized sodium is

an important factor in the regulation of the acid-base balance in the body.

3.

Cell permeability: the sodium pump- Na+

, K+

-ATPase is associated with glucose metabolismand cellular exchange of ionized sodium. In this active transport mechanism , sodium is essential

to the passage of metabolic materials through cell walls.

4. Normal muscle irritability: sodium ions play a large part in transmitting electrochemical impulses

along nerve and muscle membranes and therefore in maintaining normal muscle irritability or

excitability.

Clinical problems:

Fluid-electrolyte and acid-base balance:

Muscle action: abnormal serum levels of sodium adversely affect the functions of muscles- for example

heart muscle.

Sodium requirement: adults 2 to 3 g daily. 2 g sodium would equal about 5 g salt ( 1 tsp).

Food sources: NaCl. Natural food sources include milk, meat, eggs, certain vegetables such as carrots,

beets, spinach, and other leafy greens, celery and asparagus.

Potassium:


1. Fluid-electrolyte balance

2. Acid-base balance

3. Muscle activity: ionized potassium plays a significant role in the activity of striated skeletal

muscle and cardiac muscle.

4.

Carbohydrate metabolism: when blood glucose is converted to glycogen for storage, 0.36 mmolof potassium is stored for each 1 g of glycogen. When a patent in diabetic acidosis is treated

with insulin and glucose, glycogen, glycogen is rapidly produced and stored, drawing potassium

from the serum. Serious hypokalemia can result unless adequate potassium replacement

accompanies.

5. Protein synthesis: potassium is required for the storage of nitrogen in the muscle protein and

general cell protein.

Clinical problems:

Hyperkalemia: elevated potassium levels occur in renal failure, which prevents the normal adjustment

and clearance of ionized potassium and causes potassium to rise to toxic levels. Hyperkalemia bringsweakening of the heart action, mental confusion, poor respiration caused by weakening of the

respiratory muscles, and numbness of extremities.

Hypokalemia: decreased serum potassium of dangerous degrees may be caused by prolonged wasting

disease with tissue destruction and malnutrition or prolonged gastrointestinal loss of potassium, as in

diarrhea, vomiting, or gastric sunction. Continuous use of some diuretic drugs, increases ionized

potassium excretion and may leave the serum potassium levels abnormally low. Heart failure and

subsequent depletion of ionized potassium in heart muscle make myocardial tissue more sensitive to

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digitalis toxicity and arrhythmia (irregular contractions). To prevent these complications of cardiac

failure, potassium is usually given, especially when potassium-depleting diuretics are used.

Hypertension: inadequate intake of potassium contributes to the development of essential hypertension

and high potassium intake will lower blood pressure.

Requirement: The RDA standard estimates a minimum daily intake for a healthy adult of 2000 mg. the

usual diet contains about 1500 to 4000 mg daily, which is ample for common need.

Food sources:potassium is widely distributed in natural foods. Legumes, whole grains, fruits such asoranges and bananas, leafy vegetables, broccoli, potatoes, and meats supply considerable amounts.

Chlorine (Chloride):


1.

Acid-base balance

2. Gastric acidity: chloride secreted by the mucosa of the stomach in gastric hydrochloric acid,

provides the necessary acidic medium for digestion in the stomach and for the activation of

enzymes such as conversion of pepsinogen to active pepsin for initial protein-splitting.

Clinical problems:

1.

Gastrointestinal disorders: large amounts of chloride may be lost during continued vomiting,

diarrhea. This loss would add the complications of hypochloremic alkalosis to the clinical state of

dehydration.

2. Alkalosis: when gastric secretions and the component HCL are lost, bicarbonate replaces the

depleted chloride ions. A type of metabolic alkalosis called hypochloremic alkalosis results.

3. Endocrine disorder: Cushing's disease is an endocrine disorder caused by hyperactivity of the

adrenal cortex or by excessive quantities of adrenocorticotropic hormone (ACTH) or cortisone

given as therapy. It may produce hypokalemia, with resulting hypochloremic alkalosis.

Requirements

The RDA is a minimum daily need for healthy adults of 750 mg. adequate sodium intake = adequate

chloride intake.

Food sources: NaCl

Sulfur:


1.

Maintenance of protein structure: disulfide linkages (-S-S-) form an important secondary

structure between parallel peptide chains to maintain the structural stability of proteins.

2.

Enzyme activity: many enzymes need a free sulfhydryl group (-SH) for their activity. Therefore,sulfur participates in tissue respiration.

3. Energy metabolism: the sulfhydryl group also forms a high-energy sulfur bond similar to the

high-energy phosphate bond.

4. Detoxification: sulfur participates in several important detoxification reactions by which toxic

materials are conjugated with active sulfate and converted to a nontoxic form for excretion in

the urine.

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Clinical problems:

1. Cystine renal calculi: a relatively rare hereditary defect in renal tubular reabsorption of the

amino acid cystine causes excessive urinary excretion of cystine, cystinuria and repeated

production of kidney stones formed of cystine crystals. This type of renal calculus is yellowish in

color because of the high sulfur content. A low methionine diet is given to reduce the intake and

synthesis of these sulfur containing amino acids.

Sulfur requirement: no quantitative requirement has been specified for sulfur.

Food sources: proteins containing methionine and cystine.

Trace elements:

Iron:

Metabolic function:

1. Oxygen transport: iron is the core of the heme molecule, which is the fundamental non-protein

conjugate of hemoglobin in the red blood cells. As such iron functions as a major transporter of

vital oxygen to the cells for respiration and metabolism. Iron is also a constituent of the similar

compound myoglobin in muscle tissue.

2.

Cellular oxidation: iron functions in the cells as a vital component of enzyme system for

oxidation of glucose to produce energy. For example, iron is a constituent of the cytochrome

compounds, which are part of the electron transport system producing high-energy ATP bonds.

Clinical problems:

1. Anemia: blood condition characterized by decrease in number of circulating red blood cells,

hemoglobin.

Iron requirement: adult 10 mg /day for men and 15 mg/day for pregnant women.

Food sources:liver, meats, seafood, egg yolk, whole grains, legumes, green leafy vegetables and nuts.

Iodine:

Metabolic function:

Iodine participates in the synthesis of thyroid hormone. The thyroid hormone, thyroxine stimulates cell

oxidation and regulates basal metabolic rate, increasing oxygen uptake and reaction rates of enzyme

systems handling glucose.

Clinical problems:

Goiter: characterized by great enlargement of the thyroid gland.

Iodine requirement: adult 100 to 200 mcg of iodine daily.

Food sources: iodized salt.

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Zinc

Metabolic functions

1. Enzyme component: essential constituents of cell enzyme systems such as carbonic anhydrase,

lactate dehydrogenase, glutamate dehydrogenase, alkaline phosphatase, superoxide dismutase,

and thymidine kinase. It is nosurprise, therefore, that a deficiency of zinc brings multiple

repercussions in the dysfunction of many body systems.

2.

Carboxipeptidase: zinc is a cofactor in this protein-splitting enzyme that removes amino acidsone at a time from the C-terminus of proteins. Zinc therefore has a key role in protein digestion.

3. Carbonic anhydrase: this enzyme, of which zinc is an integral part , acts as a carbon dioxide

carrier in red blood cells, and catalyzes the reaction. It takes up carbon dioxide from cells,

combines it with water to form carbonic acid (H2CO3) and then releases carbon dioxide from the

capillaries into the alveoli of the lung. This enzyme also functions in the renal tubule cells in the

maintenance of acid-base balance, in mucosal cells , and in glands of the body.

4.

Lactate dehydrogenase: as a part of this enzyme, zinc is essential for the inter conversion of

pyruvate and lactate in the glycolytic path way for glucose oxidation. Thus zinc also plays a part

in carbohydrate metabolism.

Clinical problems

1. Hypogonadism: diminished function of gonads and dwarfism from pronounced human zinc

deficiency during growth periods.

2.

Hypogeusia and hyposmia: impaired taste (hypogeusia) and smell (hyposmia).

3. Wound healing:

4. Chronic illness in ageing: older patients with poor appetites who subsist on marginal diets and

have unhealed wounds and illness may be particularly vulnerable to zinc deficiency. As a result

of such deficiency, they often suffer from reduced immune function.

5. Acrodermatitis enteropathica: it is a rare autosomal recessive genetic disease characterized by

typical symptoms of zinc deficiency such as hair loss, skin lesions, diarrhea, and mal--digestion.

6. Mal-absorption disease: zinc deficiency is associated with mal-absorption disease when lesions

in the mucosal surface hinder its absorption. Causes of the deficiency include impaired intestinalabsorption, increased losses with attendant diarrhea and low zinc intake caused by anorexia.

Zinc requirement

The RDA standards recommends a daily adult intake of 12 to 15 mg , with 10 to 15 mg for children and 5

mg for infants.

Food sources: the best sources are seafood, meat, and eggs, and less rich sources are legumes and

whole grains. Because animal food sources supply the major portion of dietary zinc, pure vegetarians,

especially women, may be at risk for marginal zinc deficiency.

Copper

Metabolic function

1. Cooper is associated with iron in several important metabolic functions such as cytochrome

oxidation system and hemoglobin synthesis.

2. Metalloprotein enzymes: copper is a constituent of a number of important catalytic processes

through its role as a component of many cell enzymes. Some of these enzymes include

tyrosinase, monoamine oxidase, superoxide dismutase, and cytochrome oxidadase.

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Clinical problems:

1 Hypocupremia, owing to urinary loss of ceruplasmin in patient suffering from nephrosis, a wasting

renal disease

3.Genetic disease: (a) Wilson's disease: it is an autosomal recessive defect in the incorporation of copper

into the apoprotein to form ceruloplasmin. The patients have an impaired ability of the liver to excretecopper into the bile. Thus copper retention increases, bringing damage to the liver, brain, kidney and

cornea. (b) Menkes syndrome: commonly called "kinky (or steely) hair syndrome" is an X-linked

disorder of intestinal copper absorption. Here the transport of copper across the serosal membrane of

the intestinal wall for movement into the bloodstream is defective.

Copper requirement:

Adults 1.5 to 3.0 mg/day

Infants 0.4 to 0.7 mg /day

Children and adolescent 0.7 to 2.5 mg /day

Food sources of copper:

Copper is widely distributed in natural foods. Its main sources include meat, shellfish, nuts, seeds,

Manganese


1. Protein metabolism: manganese activates much amino acid inter conversion with specific

enzymes such as arginase, cysteine desulfhtdarase, dipeptidases, and leucine aminopeptidase.

2. Carbohydrate metabolism: manganese activates several conversion reactions of the glycolytic

pathway and citric acid cycle in glucose oxidation.

3. Fat metabolism: manganese activates the serum fat-clearing factor, lipoprotein lipase and

operates as a cofactor in the synthesis of long-chain fatty acids and cholesterol.

Clinical problems

Manganese deficiency: low serum manganese levels have been reported in diabetes and pancreatic

insufficiency and are found in protein-calorie malnutrition states such as kwashiorkor.

Manganese toxicity: an industrial disease syndrome, inhalation toxicity, occurs in miners and other

workers who undergo prolonged exposure to manganese dust. The excess manganese accumulates in

the liver and central nervous system eventually producing severe neuromuscular symptomsthat

resembles those of Parkinson's disease. a form of manganese neurotoxicity associated with dopamine

function and neurologic disorder has been due to poor diets and large alcohol intakes. Deficiencies of

two key nutrients that effectively inhibit dopamine oxidation result vitamin C (poor diet) and thiamin

(excessive alcohol) .

Manganese requirement:

Adults 5 mg daily

Adolescents 2 to 5 mg daily

Children 1 to 3 mg daily

Infants 0.3 to 1 mg daily.

Cereal grains, legumes, nuts, leafy vegetables, tea and coffee. Animal food sources are relatively poor

sources.

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Chromium:


It is an essential component of the organic complexes glucose-tolerance factor. This factor potentiates

the action of insulin, by facilitating the binding of insulin in cell membranes by forming a bridge between

the insulin molecule and the membrane.

Clinical problems

Diabetes mellitus: there is a positive relationship between chromium and GTF to insulin activity and

glucose tolerance.

Lipid disorder: significant reductions in serum cholesterol have been observed in patients treated with

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