Essentials of BiologySylvia S. Mader

Chapter 25Lecture Outline

Prepared by: Dr. Stephen EbbsSouthern Illinois University Carbondale

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

25.1 Nutrition

• All aspects of bodily function depend upon proper nutrition.

• A nutrient is a component of food that is needed for a specific physiological function.

• Deficiency disorders occur when the body lacks a nutrient required for a function.

25.2 The Classes of Nutrients

• There are six classes of essential nutrients.– Carbohydrates– Lipids– Proteins and amino acids– Minerals– Vitamins– Water

• These nutrients may be needed in large amounts (macronutrients) or small amounts (micronutrients).

Introducing the Nutrients (cont.)CLASS ROLE Macro or micro?

Carbohydrates Energy, fiber Macronutrient

Lipids Energy, insulation, vitamin D synthesis

Macronutrient

Proteins Provides essential amino acids

Macronutrient

Minerals Homeostasis, water balance, cofactors

Micronutrient

Vitamins Metabolism and development

Micronutrient

Water Hydration, temperature control

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Carbohydrates

• Carbohydrates include sugars, starch and fiber.

• Sugars can be present as monosaccharides such as glucose or disaccharides such as sucrose.

• Starch is a polymer used by plants to store glucose.

Fiber

• Fiber is the indigestible carbohydrates derived from plant material.

• Fiber is not considered a nutrient because it cannot be digested to smaller molecules.

• Insoluble fiber is important because it stimulates movement of feces in the bowel.

• Soluble fiber binds to compounds in the intestine to deter their absorption and enhance their excretion.

Fiber (cont.)

Can Carbohydrates Be Harmful?

• Carbohydrates are important because they provide about 45% of the body’s energy needs.

• A diet containing large amounts of low-fiber carbohydrates adds empty calories to the diet.

• Excess carbohydrates in the diet can contribute to obesity, diabetes, and other diseases.

Lipids

• There are different forms of lipids that influence nutrition.– Triglycerides such as fats and oils supply cells with

energy.

– Fat is a long-term storage form for lipids.

• Triglycerides are necessary for nutrition.– Nutritionists recommend that fats and oils should

provide 30-35% of the body’s energy.– Triglycerides contain essential fatty acids that the

body requires for proper function.

Can Lipids Be Harmful?

• Cholesterol is a lipid that serves an important function in cells.

• However, elevated levels of cholesterol and fats in the blood can be detrimental to health.

• Lipids should not be eliminated from the diet, but should be consumed in moderation from more nutritional sources.

Proteins

• Proteins consumed in the diet are broken down to liberate amino acids, nine of which are essential in the diet.

• While all foods contain protein, plant proteins are considered “incomplete” because they generally lack one or more of the essential amino acids.

• This limitation can be overcome by eating specific combinations of plant foods.

Can Proteins Be Harmful?

• Proteins should supply no more than 10-15% of the calories consumed in the diet.

• Excess protein in the diet cannot be used productively and is generally excreted as urea in the urine.

• High protein diets can lead to some health problems, such as dehydration, calcium loss, and kidney stones.

Minerals

• The term minerals is applied to the 20 elements that are required for nutrition.

• Absence of a specific mineral can lead to mineral deficiencies.– Low iron can lead to anemia.– Low calcium can lead to osteoporosis.

• Excess minerals in the diet, such as sodium, can also have harmful effects.

Minerals (cont.)

Major minerals Primary Functions

Calcium Strengthen bones, nerve function

Phosphorus Bone growth, energy metabolism

Potassium Nerve function, muscle contraction

Sodium Nerve function, pH and water balance

Chloride Water balance

Magnesium Nerve and muscle function

Minerals (cont.)

Trace minerals Primary Functions

Zinc Protein synthesis, immune function

Iron Hemoglobin synthesis

Copper Hemoglobin synthesis

Iodine Thyroid hormone synthesis

Selenium Antioxidant

Vitamins

• Vitamins are essential organic compounds other than carbohydrates, lipids, and proteins that regulate metabolic activities.

• Vitamins contribute primarily to energy metabolism and antioxidant defenses.

• Vitamin deficiencies can lead to serious disease.

Vitamins (cont.)

Water-soluble vitamin Primary functions

Vitamin C Antioxidant, maintains capillaries, bones, & teeth

Thiamine (B12) Important coenzyme, activity of nervous system

Riboflavin (B2) Coenzyme for energy, fat, & protein metabolism

Niacin Coenzyme for energy, fat, & protein metabolism

Vitamins (cont.)

Water-soluble vitamin Primary functions

Folic acid Helps form hemoglobin

Vitamin B6 Helps form hemoglobin

Pantothenic acid Coenzyme for fat & carbohydrate metabolism

Vitamin B12 Coenzyme for DNA synthesis

Biotin Coenzyme for amino acid and fatty acid metabolism

Vitamins (cont.)

Fat-soluble vitamin Primary functions

Vitamin D Bone and teeth development

Vitamin E Antioxidant

Vitamin K Synthesis of clotting factors

Water

• The body of animals is about 60% water.

• Water also contributes to a number of chemical reactions.

• Water is also important to the movement of food through the intestine.

25.3 Nutrition and Health

• In the United States, poor nutrition is a significant factor in human disease.

• For example, excess body fat contributes to diabetes, heart disease, and certain forms of cancer.

Are You Overweight?

• The body mass index (BMI) is to determine if someone is overweight.

• The BMI is calculated with this formula.

2

weight (pounds) x 703.1

height (inches)BMI =

Normal ObeseOverweight Very obese18.5 25.0 30.0 40.0BMI

value

Energy Intake Versus Energy Output

• Aside from genetics, another factor that contributes to obesity is a greater intake of energy than energy output.

• Energy intake is expressed as the number of kilocalories provided by the food eaten.

• Energy output can be measured based upon body weight and physical activity.

Disorders Associated with Obesity

• There are two common diseases associated with obesity.– In type 2 diabetes, the body develops

impaired insulin production and increased insulin resistance, which leads to increased fat deposition and elevated fatty acid levels.

– Cardiovascular disease affects the heart and can lead to hypertension, heart attack, and stroke.

Eating Disorders

• Social, cultural, emotional, and biological factors all contribute to eating disorders.– Anorexia nervosa is a psychological disorder

in which the person is afraid to eat for fear of gaining weight.

– People with bulimia nervosa undergo binge-purge eating behavior.

– Some people have binge-eating disorders.– People with muscle dysmorphia are fixated

upon their muscular development.

The Food Pyramid

• There are numerous guides, such as the Food Pyramid, that can help consumers plan nutritious meals.

• In 2005, the USDA released a new food pyramid to help Americans achieve proper nutrition.

The Food Pyramid (cont.)

Making Sense of Nutrition Labels

• The Nutrition Facts panel on all foods contains dietary information about that food.– The serving size indicates the amount of that product

that is typically consumed in one sitting.– The number of calories represent the kilocalories of

energy provided by that serving.– The percent daily value indicates what fraction of the

recommended total daily amount for that nutrient that would be obtained from consumption of that serving.

Making Sense of Nutrition Labels (cont.)

Dietary Supplements

• Dietary supplements are nutrients and plant products that can enhance health.

• Dietary supplements are regulated as foods are, so the health benefit of a supplement may be exaggerated.

• Dietary supplements can be detrimental if too much is taken.