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Kin 110 Lecture 6

Vitamins Ch. 8

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Learning Objectives• Define vitamin• Classify vitamins as fat-soluble or

water-soluble• List the major functions and

deficiency symptoms for each fat-soluble vitamin

• List three important food sources for each fat-soluble vitamin

• Describe toxicity symptoms for excess consumption of certain fat-soluble vitamins

• Evaluate the use of vitamin supplements - risk / benefit

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Vitamins• Vitamin – essential organic (contains

carbon) substances needed in small amounts in diet

• Required for normal function, growth, maintenance of body structures

• Yield no energy, but participate in energy yielding reactions

• fat soluble vitamins - ADEK • water soluble vitamins-B vitamins and C

• co-enzymes – help enzymes function– B vitamins and vitamin K

– Fig. 8-1

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Vitamins• To be classified as vitamin

– Body unable to synthesize enough – Absence for a defined period of time

must produce deficiency (fig 8.2)– symptoms, if caught in time, are cured

when substance is reintroduced to diet

• Megadoses of Vitamins– Requires Medical supervision

• Toxicity diseases are possible• Many unproven claims continually being

made

– Niacin - cholesterol lowering– Vit D - treatment of psoriasis

• Have they all been found?– People living on intravenous solutions

of Protein, Carbohydrates, Fat and all known vitamins and minerals survive, grow, reproduce and fight disease

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Storage of Vitamins

• Fat soluble vitamins A, E and D not readily excreted

• Water soluble - lost from body quite rapidly (B6 and B12 stored)

• In general, limited storage of vitamins– should be consumed daily

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Vitamin Toxicity• Toxicity theoretical for all vitamins• Fat soluble more frequently observe

toxicity (A and D)• E, Niacin, B-6 and C – very large

amounts needed to result in toxicity– Only possible from supplements

• A and D only 3-5 times RDA needed on a regular basis for toxicity– Vit A – important to minimize in early

pregnancy

– Once a day vitamins, less than 2 times daily value – not a risk

• Preserving vitamin content - Table 8.1

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Fat soluble Vitamins

• ADEK– Table 8.2

• Absorbed along with dietary fat• Travel in bloodstream along with fat

to reach body cells• Stored in liver and fatty tissue• 40-90 % of fat sol. vit. absorbed• Can be reduced further –

interference in normal digestion and absorption of fats.– Eg. Mineral oil laxatives

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Vitamin A• Easy to over dose (toxic) and be

deficient– Both cause severe problems

• Variety of forms• Retinoids

– Preformed vitamin A –– Only found in animal foods

• Carotenoids – pro-vitamin A – plants– Yellow-orange pigment in carrots– Turned into vitamin A as needed– Most potent form is beta-carotene

• Both pre and pro – referred to as Vitamin A

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Functions of Vitamin A• Many roles – not all well understood• Role in vision – best known and

most clearly understood– Performs important functions is both

light (day) and dark (night) vision– in dim light, one form of A is required

to start the chemical process that signals the brain that light is striking the eye.

• Without vit A – night blindness• Prolonged deficiency – cells unable

to produce mucus for cornea– Dry, dirty, scratched, infected – Xeropthalmia - dry eye

• Less-developed nations – children– Blindness. Infection, death

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Health of Cells• Vitamin A – maintains health of all

cells that line internal and external surfaces – Lungs, intestines, stomach, eyes, skin

(epithelial cells)– Cells secrete mucus – lubricant– Without A – decrease activity of

immune cells, increased infection

• Carotenoids play a role in preventing cardiovascular disease

• Needed for growth, Development and Reproduction– Synthesis of proteins that stimulate

proper growth and development– Resorbing and producing bone

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Cancer and Vitamin A• Skin, lung, bladder and breast cancer• Adequate intake of vitamin A can

lower risk of breast cancer– Megadoses NOT recommended to

prevent cancer

• Carotenoids – trap energy in free radicals – oxidation can initiate cancer process– Supplements of -carotene not

effective– Variety of fresh fruits and vegetables– Lycopene - tomatoes - may prevent

prostate cancer

• Acne – topical and internal derivatives – May produce birth defects in pregnant

women using treatments– Eg retin-A and accutane

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Vitamin A in Food• Preformed vitamin A

– liver, fish oils, fortified milk and cereal, butter, margarine, eggs

• Pro-vitamin – dark green and orange vegetables– Carrots, spinach, winter squash, papaya,

apricots, sweet potatoes

• RDA – RAE- retinol activity equivalent– 900 g RAE (males)– 700 g RAE (females)

• Due to difficulty in classifying contributions from preformed and pro-vitamin A sources the labeling has undergone changes recently– Very old - IU, old RA, now RAE

• Risk of deficiency – children, poor, alcoholics

• Dietary sources table – fig 8.3

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Toxicity of Vitamin A• 3 times the RDA can cause problems

if continued for prolonged periods• Early pregnancy (pre-formed)

– Fetal malformations, birth defects, spontaneous abortion

• Non-pregnant – skin, hair, internal organs and CNS– Permanent damage can occur

• Vit A is stored for months– Women in childbearing years – limit to

100% intake -one ounce of liver - 300%

• Carotenoids (pro form) not toxic– Rate of conversion is slow– Efficiency of absorption decreases as

intake increases

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Vitamin D

• Also considered a hormone– skin cells convert cholesterol like

substance into vitamin D using sunlight

• effects kidney and bone

• 10-15 minutes of exposure of arms, face and hands; 2-3 times per week– not effective in winter– must have vitamin intake

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Functions of Vitamin D

• To become active hormone, vitamin D must be activated in liver and kidneys

• calcitrol - active form• regulates calcium and bone

metabolism along with parathyroid hormone– regulates absorption of calcium and

phosphate from intestines– reduces kidney excretion of calcium– regulates deposition of calcium in

bones• Immune system and skin development

influenced by vitamin D

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Vitamin D and Bone• Calcium and phosphorus deposition• without vit D bones weaken and bow

under pressure– Rickets (children)– fortification of milk -– malabsorption of fat (cystic fibrosis)

• osteomalacia - adults - soft bones– calcium withdrawn from bones – inefficient absorption or conservation– vit D deficient– bones porous and weak - break easily– supplement vit D - reduces fractures– problem with vitamin D activation or

absorption

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Dietary Sources of D• Fatty fish (sardines, salmon),

fortified milk, yogurt and cereals – under 51 years - 5 g/day– over 51 2-3 times - 10-15 g/day– max. 50 g /day– Young, fair skinned 10-15 min of sun

on face and arms 2-3 times /week

• 5-10 times recommended on regular basis results in toxicity– calcium over absorption - deposition in

kidneys and other organs– high blood calcium– Weakness, loss of appetite, diarrhea,

vomiting , mental confusion, – sun exposure does not result in toxicity

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Vitamin E

• Fat soluble antioxidant - • resides in cell membranes• donates electrons - protection from

free radicals• fig 8-4• DNA oxidation - cancer, cell death

– repair mechanisms for damage

• impact on cancer, heart disease very minimal compared to proper diet and exercise– not an alternative to making good

overall health choices

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Deficiency of vitamin E• Few women getting enough vitamin

E from food– Supplements not as potent– Smoking destroys vitamin E

• Cell membranes break down– red blood cell breakdown in infants– unsaturated fatty acids susceptible to

oxidation– hemolysis- breaking of rbc in absence

of vit. E

• vit E improves vit A absorption• used to metabolize iron in cell,

maintain nervous tissue, and insulin function

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Vitamin E in Foods• plant oils, fortified cereals, fruits and

vegetables, eggs, margarine– Sunflower seeds and almonds are an

excellent source of vitamin E– vitamin E in plant oils - protects

unsaturated fatty acids– Animal foods almost no vitamin E

• content of vit E depends on harvesting , processing storage and cooking– easily destroyed by oxygen, metals ,

light , repeated frying

• RNI - 15 mg /day• alpha tocopherol - most active form• megadose therapy - not proven

– Upper level is 1000mg of supplement– toxicity not a problem, except for

people on anticoagulants (CVD) or with a vitamin K deficiency - due to increasesd risk of hemorrhage

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Vitamin K• Family of compounds known

collectively as vitamin K• Found in plant oils, fish oils, and

meats– One form is synthesized by bacteria in

the intestine (10% of need)

• role - vital for blood clotting– synthesis of blood clotting factors

• formation of proteins in bone, kidney and muscle– impart calcium binding potential

• newborns lack bacteria to produce vitamin K– routine injection at birth

• deficiency in adults on prolonged antibiotics or with poor fat absorption

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Vitamin K in Food

• Liver, green leafy vegetables, broccoli, peas and green beans– Also soybean and canola oils

• vitamin K not stored well - one day– abundant in diet, deficiency uncommon

– resistant to cooking

• RDA - 90-120 g / day– no risk of toxicity

– risk of reduced effectiveness of medications to reduce blood clotting (CVD)

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Vitamin Supplements• Supplements may be beneficial, and

improve health of population– Most unwilling to increase intake of

fruits and vegetables

• folate (B vitamin)– birth defects– homocystien - risk factor for heart

disease– alleviated by adequate folate (and

reduction in red meat)

• vitamin B12 - risk over 50 – synthetic more easily absorbed

• Eat right and take a multivitamin– Use supplements in consultation with

physician– Potential impacts of medications for

CVD and cancer

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Vitamin Supplements• Megadoses of E and B12

– trials ongoing, may be beneficial

– Vit E not very exciting results

• Supplements should be taken with or just after meal

• no more than 100% of daily values– avoid excess selenium and C

• overabsorption of iron

– males avoid excess iron

– excess zinc - inhibits iron an copper absorption

– excess folate - masks B12 deficiency

– avoid other products - PABA, inositol, bee pollen, lecithin