Nutrition

Chapter 15a

All the chemical reactions in a person’s body constitute that person’s metabolism

Catabolic processes break down nutrients to obtain energy & raw materials

Anabolic processes use energy to assemble cells & tissues

The calorie is a measure of the amount of energy in food

• The calorie is the metric unit of energy, the amount of energy necessary to raise the temperature of 1 mL of water by 1oC

• Though they are still called “calories”, food calories, or Calories, are actually kilocalories, equal to 1000 regular calories

How calories can be measured

1. All living things are composed of 4 common macromolecules

• Nucleic Acids• Proteins• Carbohydrates• Lipids• DNA is a nucleic acid

Nucleic acids and Proteins

Nucleic acids- DNA

Proteins, made of amino acids

Carbohydrates and LipidsCarbohydrates- glucose+ fructose= sucrose

Lipids- a fat molecule made of glycerol and 3 fatty acids

Vitamins and Minerals

• There are 13 vitamins, and various minerals which the body must obtain through diet

• Vitamins and minerals often function as cofactors in enzymes

• Because cofactors are recycled, vitamins are required in minute quantities

Human metabolism is diverse but limited

• Though the body can manufacture many of its own necessary parts, essential nutrients cannot be manufactured and must be obtained through diet

• Essential amino acids are required to make all proteins

• Essential fatty acids are required for cell signaling

Nutrients

• Food provides – Fuel for cellular activities – Metabolic regulators– Building blocks for • Cell division• Maintenance• Repair

We also need water…

• Water is necessary for – Proper cellular

environments – Certain cellular reactions

Nutrients

• A nutrient is a substance in food that – Provides energy – Plays a structural or functional role to promote

normal growth, maintenance, or repair

Lipids

Lipids

• Lipids – Fats– Oils – Cholesterol

• 95% of the lipids found in food are triglycerides – Consist of a molecules

made from three fatty acids attached to a molecule of glycerol

Lipids

• Fat – A ready source of energy– Insulation and a cushion for vital organs– Components of the cell membrane– Construction of myelin sheaths– Absorption of fat-soluble vitamins

Lipids

• Fatty acids differ in their degree of saturation

• Saturated fats – Solid at room

temperature – Most come from animal

sources

• Unsaturated fats – Liquid at room

temperature – Come from plant sources

Lipids

• A high-fat diet is associated with – Obesity – High blood pressure– Atherosclerosis – Increased risk of diabetes – Certain cancers• E.g., colon, prostate, lung

Cholesterol• Cholesterol – The structural basis for

the steroid hormones – Low-density lipoproteins

(LDLs) • Bad

– They deposit cholesterol in the artery walls

– High-density lipoproteins (HDLs) • Good

– They help the body to eliminate cholesterol

Fats in the diet

• Only 20 to 30% of the calories in the diet should come from fats– Most of those should be

monounsaturated and polyunsaturated fats

Carbohydrates

Carbohydrates

• Carbohydrates – Provide fuel for our bodies – Found in our diet as sugars, starches, and fiber

Carbohydrates

• Dietary fiber – A carbohydrate in plant foods that humans cannot

digest – Good for the heart and blood vessels • It lowers LDLs but does not lower the beneficial HDLs

Carbohydrates

• 45 to 65% of the calories in our diet should come from carbohydrates, including both – Simple carbohydrates • Sugars

– Complex carbohydrates • Starches and fiber

Figure 15a.3

Carbohydrates• The glycemic response

– A measure of how quickly a serving of food is converted to blood sugar

• The glycemic index – A numerical ranking of

carbohydrates based on their glycemic response

• Foods with a low glycemic index help to reduce the risk of heart disease and diabetes

Proteins

Proteins

• Proteins – The structural components of every cell– Regulate body processes– Are antibodies– Can be used for energy

Proteins• Proteins – Chains of amino acids that are

digested and delivered to the cells

• Human proteins contain 20 different kinds of amino acids– The human body can synthesize

11 of the amino acids– The remaining 9 must be

supplied by the diet • Essential amino acids

Proteins

• Complete dietary proteins – Contain all 9 of the

essential amino acids that your body cannot synthesize

• Incomplete proteins – Lack one or more of the

essential amino acids

Proteins

• Complementary proteins – Combinations of

proteins that together supply enough of all the essential amino acids

Proteins

• 10 to 35% of the calories in our diet should come from a combination of plant and animal proteins

Vitamins and Minerals

Vitamins & Minerals

• Vitamins – Organic compounds that are needed in minute

quantities – Usually function as coenzymes

Vitamins

Table 15a.2 (1 of 2)

Table 15a.2 (2 of 2)

Nutrients

• Vitamins – Water-soluble – Fat-soluble

• Except for vitamin D, our cells cannot make vitamins and must obtain them from food

Nutrients

• Minerals are inorganic substances that are essential to a healthy diet

Minerals

Table 15a.3 (1 of 2)

Minerals

Table 15a.3 (2 of 2)

Water

• Water – Transports materials through our blood and lymph– Provides a medium for chemical reactions– Is a lubricant– Can serve as a protective cushion– Plays an important role in the regulation of body

temperature

Nutrition and Weight Control

• MyPyramid is a food guide for planning a healthy diet

• Nutrients provide energy or have a structural or functional role in the body

• Food labels help us make wise food choices • For body energy balance, calories gained in

food must equal calories used

MyPyramid Is a Food Guide for Planning a Healthy Diet

• MyPyramid – A food guide released by the U.S. Department of

Agriculture (USDA) in 2005 for planning a healthy diet

MyPyramid Is a Food Guide for Planning a Healthy Diet

Figure 15a.1

MyPyramid Is a Food Guide for Planning a Healthy Diet

Figure 15a.1 (1 of 2)

MyPyramid Is a Food Guide for Planning a Healthy Diet

Figure 15a.1 (2 of 2)

MyPyramid Is a Food Guide

• A healthy lifestyle includes – Choosing food wisely– Staying within your calorie needs– Engaging in physical activity

Food Labels Help Us Make Wise Choices

• Using the information on food labels can help you make healthy choices and compare different brands and ingredients

Food Labels Help Us Make Wise Choices

Figure 15a.6 (1 of 2)

Food labels can be misleading

Figure 15a.6 (2 of 2)

Body Energy Balancing

• Body’s energy balance depends on – The calories

gained in food – The calories used

• Unused food energy is stored – Fat – Glycogen

Body Energy Balancing

• The body requires energy for maintenance of – Basic body functions

• Basal metabolic rate (BMR)

– Physical activity– Processing of the food

that is eaten

Body Energy Balancing

• Dietary guidelines for Americans include – Fitness– Making healthy food choices – Avoiding foods that lead to disease

Nutrition and Weight Control

• Obesity is body weight 20% or more above the body weight standard

• Successful weight loss programs usually involve reducing calorie intake, increasing calorie use, and changing behavior

• Anorexia nervosa and bulimia are eating disorders that create caloric deficits

Obesity

• Obesity – Body weight 20% or more above the body weight

standard

Obesity

• The Body Mass Index (BMI)– Evaluates your weight in

relation to your height – Does not actually

measure % body fat– Statistically correlates

pretty well, but there are exceptions

Obesity

• Maintaining a healthy weight is important to avoid cardiovascular disease, diabetes, and degenerative joint disease

BMI does not correlate perfectly to percent body fat

Weight Loss Programs

Figure 15a.8

Anorexia Nervosa and Bulimia

• Weight loss can be dangerous – Anorexia nervosa

• highest mortality rate of any psychiatric disorder

– Bulimia• Intentional vomiting after eating• Both can be fatal

• Eating habits associated with these disorders is thought to be the result of physiological, social, and psychological factors