Chapter 18 Nutrition and Metabolism

2402 Anatomy and Physiology II Chapter 18 Susan Gossett [email_address] Department of Biology Paris Junior College

Hole’s Human Anatomy and Physiology Twelfth Edition Shier  Butler  Lewis Chapter 18 Nutrition and Metabolism Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

18.1: Introduction
The human body requires fuel as well as materials to develop, grow and heal
Nutrients are chemical substances supplied by the environment required for survival
Macronutrients
Carbohydrates
Proteins
Fats
Micronutrients
Vitamins
Minerals
Essential nutrients
Nutrients human cells cannot synthesize such as certain amino acids

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fat cells Bloodstream Bloodstream excessive insufficient Appetite Appetite suppressed Appetite enhanced Fasting + + + + + – – Stimulation Inhibition Adipocytes synthesize fat and secrete leptin into bloodstream Leptin increases metabolic rate. Food intake in excess of caloric needs Leptin inhibits neuropeptide Y release from the hypothalamus Cells in stomach secrete ghrelin Ghrelin stimulates release of neuropeptide Y from the hypothalamus Release into bloodstream

18.2: Carbohydrates
Carbohydrates are organic compounds and include the sugars and starches
The energy in their chemical bonds are used to power cellular processes
Excesses lead to:
Obesity
Dental caries
Nutritional deficits
Deficiencies lead to:
Metabolic acidosis
Weight loss

Carbohydrate Sources
Carbohydrates are ingested in a variety of forms:
Complex carbohydrates are polysaccharides that include:
Starch from plant foods
Glycogen from meats
Simple carbohydrates are:
Disaccharides from milk sugar, cane sugar, beet sugar and molasses
Monosaccharides from honey and fruits
Digestion breaks complex carbohydrates into monosaccharides that are small enough to be absorbed
Cellulose is a complex carbohydrate abundant in our food
It is not digested, but provides bulk (fiber or roughage)

Carbohydrate Use
Monosaccharides that are absorbed include fructose, galactose, and glucose
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycogen Fat Starch Sucrose Maltose Lactose Carbohydrates Digestion Glucose Glucose Monosaccharides (Respiration) (Glycogenesis) (Lipogenesis) Glucose and Fructose Glucose and Galactose CO 2 + H 2 O + Energy

Carbohydrate Requirements
The minimal requirements for carbohydrates in the human diet is unknown
Intake of at least 125 – 175 grams is necessary
An average diet includes 200-300 grams

18.3: Lipids
Lipids are organic compounds that include fats, oils, and fat-like substances such as phospholipids and cholesterol
They supply energy for cellular processes and help to build structures like cell membranes
The most common dietary lipids are fats called triglycerides
Excesses lead to:
Obesity
Increased serum cholesterol
Increased risk of heart diseases
Weight loss
Skin lesions
Hormonal imbalances

Lipid Sources
Triglycerides are found in plant-based and animal-based foods and include:
From plants:
Seeds, nuts and plant oils (olive, peanut and canola are the healthiest)
From animals:
Meat, eggs, milk and lard

Lipid Use
Lipids in foods are phospholipids, cholesterol and most commonly, fats (triglycerides)
They are oxidized for energy
They are stored in adipose tissue
Glycerol may be used to synthesize glucose

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Heat CO 2 + + + Energy Fats from foods Fatty acids Ketone bodies Beta oxidation Glycerol Glucose Fat Hydrolysis Citric acid cycle H 2 O ATP Acetyl coenzyme A

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cholesterol Phospholipids Fatty acids + Glycerol Digestion Triglycerides Triglycerides Lipoproteins Fatty acids (except essential fatty acids)

Lipid Requirements
The lipid content of human diets varies widely
The American Heart Association advises that the diet not exceed 30% of total daily calories from fat

18.4: Proteins
Proteins are polymers of amino acids
They have a wide variety of functions, including building more protein (structural protein, enzymes, hormones, and plasma proteins) and supplying energy
The waste product of protein metabolism is urea
Excesses lead to obesity
Extreme weight loss
Muscle wasting
Anemia
Growth retardation

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hormones Enzymes Proteins Protein Amino acids Digestion Fat Glucose Structural proteins Plasma proteins Energy + CO 2 + H 2 O

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Heat CO 2 + + Energy Proteins from foods Amino acids + Glucose Fat Urea Hydrolysis Deamination – NH 2 groups Deaminated portions (by various pathways) Acetyl coenzyme A Citric acid cycle H 2 O ATP

Protein Sources
Foods rich in proteins include:
Meats
Fish
Poultry
Cheeses
Nuts
Milk
Eggs
Cereals
To some degree legumes (beans and peas)
The body needs 20 types of amino acids; those that can be synthesized by the body are non-essential amino acids (12) and those that cannot are essential amino acids (8-10)

Nitrogen Balance
In healthy adults, protein is continuously built up and broken down
Proteins contain a high percentage of nitrogen
The amount of nitrogen taken in is equal to amount excreted
Negative nitrogen balance develops from starvation
Positive nitrogen balance develops in growing children, pregnant women, or an athlete in training

Protein Requirements
In addition to supplying essential amino acids, proteins provide nitrogen and other elements for the synthesis of non-essential amino acids and certain non-protein nitrogenous substances
The dietary amount varies according to body size, metabolic rate, and nitrogen balance condition
Typically protein intake is 10% of a person’s diet
Most people should consume 60-150 grams a day

18.5: Energy Expenditures
Carbohydrates, fats and proteins supply energy for all metabolic processes
Deficiencies can lead to death
Excesses can lead to obesity

Energy Values of Food
A calorie indicates the amount of potential energy a food contains
Calories can be measured from the content of foods
The rate that the body expends energy at rest can be measured and is known as basal metabolic rate (BMR)
This varies for:
Carbohydrates
4.1 calories per gram
Lipids
Proteins
Thermometer Food sample Insulation Platinum dish Stirrer Oxygen Electric wires for ignition of sample Water Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Energy Requirements
Basal metabolic rate (BMR):
The rate at which body expends energy at rest
This primarily reflects energy needed to support the activities of the organs
This varies with gender, body size, body temperature, and endocrine function
Energy is needed:
To maintain BMR
To support muscular activity
To maintain body temperature
For growth in children and pregnant women

Energy Balance
Energy balance occurs when caloric intake in the form of food equals caloric output from BMR and muscular activities
The body weight remains constant
If, however, caloric intake exceed output, tissues store excess nutrients
This is a positive energy balance that leads to weight gain

Desirable Weight
Most common nutritional disorders involve caloric imbalances
Desirable weight is difficult to determine
Body Mass Index (BMI) is used today to assess weight considering height
A person is classified with BMI as either underweight, normal weight, overweight, or obese
Overweight is defined as exceeding desirable weight by 10% - 20%, or a BMI of 25 and 30
Obesity occurs when a person is more than 20% above desired weight, or with a BMI over 30

18.1 Clinical Application Obesity

18.6: Vitamins
Vitamins are organic compounds, other than carbohydrates, lipids and proteins, that are essential for normal metabolic processes
Vitamins cannot be synthesized by body cells in adequate amounts
Vitamins are classified on the basis of solubility as either fat- soluble (vitamins A, D, E, and K) or water-soluble (the B vitamins and vitamin C)

Fat-Soluble Vitamins
The fat-soluble vitamins dissolve in fats and are influenced by lipids
Bile salts promote fat-soluble vitamin absorption
They are fairly resistant to heat (not destroyed by cooking and/or food processing)
Includes vitamins A, D, E, and K

Water-Soluble Vitamins
The water-soluble vitamins include the B vitamins and vitamin C
Cooking and food processing destroy them
B vitamins (six of them) are several compounds essential for normal cellular metabolism and known as the vitamin B complex

18.7: Minerals
Dietary minerals are inorganic elements that are essential in human metabolism
These are usually extracted from the soil by plants
They are obtained by humans from plant foods or animals that have eaten plants
They are responsible for roughly 4% of body weight

Characteristics of Minerals
Minerals are most concentrated in the bones and teeth
They are typically incorporated into organic molecules (phospholipids, hemoglobin and iodine in thyroxine)
They compose parts of the structural materials of all cells
Homeostatic mechanisms regulate the concentration of minerals in body fluids
Mineral toxicity can result from too much of a mineral or from overexposure to industrial pollutants, household chemicals, or certain drugs

Major Minerals

Trace Elements
Trace elements (microminerals) are essential minerals found in minute amounts, each makes up less than 0.005% of body weight
They include:
Iron
Manganese
Copper
Iodine
Cobalt
Zinc
Fluorine
Selenium
Chromium

18.8: Healthy Eating
An adequate diet provides sufficient energy (calories), essential fatty acids, essential amino acids, vitamins, and minerals to support optimal growth and to maintain and repair body tissues
Requirements vary with age, sex, growth rate, level of physical activity and stress, and genetic and environmental factors
Dietary requirements such as recommended daily allowances (RDA) are best to follow
The U.S. Department of Agriculture’s Food Pyramid is another tool to follow
Nutritional information as well as ingredients are listed on most grocery items for retail sale

Meat Sweets Eggs Poultry Fish Olive oil Fruits Fruits The Mediterranean Diet Pyramid Sweets Fats Carbohydrates Protein/Dairy Monthly Monthly Weekly Daily Meats Sweets Eggs and poultry Weekly Optional daily Daily Physical activity GRAINS MILK FRUITS OILS Activity Activity is represented by the steps and the person climbing them, as a reminder of the importance of daily physical activity. Moderation Moderation is represented by the narrowing of each food group from bottom to top. The wider base stands for foods with little or no solid fats or added sugars. These should be selected more often. The narrower top area stands for foods containing more added sugars and solid fats. The more active you are, these foods can fit into your diet. Personalization Personalization is shown by the person on the steps and the slogan. VEGE TABLES MEAT & BEANS Proportionality Proportionality is shown by the different widths of the food group bands. The widths suggest how much food a person should choose from each group. The widths are just a general guide, not exact proportions. Variety Variety is symbolized by the 6 color bands representing the 5 food groups of the Pyramid and oils. This illustrates that foods from all groups are needed each day for good health. Gradual Improvement Gradual improvement is encouraged by the slogan. It suggests that individuals Can benefit from taking small steps to improve their diet and lifestyle each day. MyPyramid.gov STEPS TO A HEALTHIER YOU U.S. Department of Agriculture Center for Nutrition Policy and Promotion April 2005 CNPP-16 Vegetables Daily Physical Activity Daily Beverage Recommendations: 6 glasses of water Wine in moderation Cheese & Yogurt Whole grains & potatoes Daily Physical Activity Beans, legumes & nuts Vegetables Fish and shell fish or dairy Vegetable oils Fruits, légumes, nuts, seeds, vegetables Rice, rice products, noodles, breads, millet, corn and other grains The Asian Diet Pyramid Sake, wine, beer, other alcoholic beverages and tea Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Olive Oil Mayo Clinic Healthy Weight Pyramid Olive Oil

Malnutrition
Malnutrition is poor nutrition that results from a lack of essential nutrients or failure to use them
Undernutrition – deficiency of essential nutrients
Overnutrition – excess of nutrient intake
Malnutrition can be a result of:
Primary malnutrition – malnutrition from diet alone
Secondary malnutrition – adequate diet but individual characteristics make the diet insufficient

18.2 Clinical Application Dietary Supplements – Proceed With Caution

Starvation
A healthy human can survive 50-70 days without food
Symptoms include low blood pressure, slow pulse, chills, dry skin, hair loss, and poor immunity
Common nutritional disorders include:
Marasmus – lack of all nutrients
Kwashiorkor – protein starvation
Anorexia nervosa – eating disorder; self-starvation
Bulimia – eating disorder; binge and purge cycle

18.3 Clinical Application Nutrition and the Athlete

18.9: Lifespan Changes
Dietary requirements remain generally the same throughout life
BMR rises in early childhood and peaks in adolescence
BMR declines in adulthood
Change in nutrition often reflects the effects of medical conditions and the social and economic circumstances

Important Points in Chapter 18: Outcomes to be Assessed
18.1: Introduction
Define nutrition, nutrients, and essential nutrients.
Explain appetite control.
18.2-18.4: Carbohydrate - Proteins
List the major sources of carbohydrates, lipids, and proteins.
Describe how cells utilize carbohydrates, lipids, and proteins.
Define nitrogen balance.
18.5: Energy Expenditures
Explain how energy values of food are determined.
Explain the factors that affect an individual’s energy requirements.
Define energy balance.

Explain what is meant by desirable weight.
18.6: Vitamins
List the fat-soluble and water-soluble vitamins and summarize the general functions of each vitamin.
18.7: Minerals
Distinguish between a vitamin and a mineral.
List the major minerals and trace elements and summarize the general functions of each.
18.8: Healthy Eating
Describe an adequate diet.
Distinguish between primary and secondary malnutrition.

18.9: Lifespan Changes
List the factors that may lead to inadequate nutrition later in life.

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Chapter 18 Nutrition and Metabolism

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