chapt18 nutrition and metabolism
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BIOL 2074: ANATOMY & PHYSIOLOGYCHAPTER 18 NUTRITION & METABOLISM
Brenda Holmes MSN/Ed, RN
Associate Professor
Biology1
South Arkansas Community College
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18.1: INTRODUCTION
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• 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
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Fat cells
Bloodstream
Bloodstream
excessive
insufficient
Appetite
Appetite suppressed
Appetite enhanced
Fasting
+
+
++
+–
–
Stimulation
Inhibition
Adipocytes synthesizefat and secrete leptininto bloodstream
Leptin increasesmetabolic rate.
Food intake in excessof caloric needs
Leptin inhibits neuropeptideY release from thehypothalamus
Cells in stomachsecrete ghrelin
Ghrelin stimulates releaseof neuropeptide Y fromthe hypothalamus
Release intobloodstream
18.2: CARBOHYDRATES
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• 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
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• 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
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• Monosaccharides that are absorbed include fructose, galactose, and glucose
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Glycogen Fat
Starch Sucrose Maltose Lactose
Carbohydrates
Digestion
Glucose Glucose
Monosaccharides
(Respiration) (Glycogenesis) (Lipogenesis)
Glucoseand
Fructose
Glucoseand
Galactose
CO2 + H2O + Energy
CARBOHYDRATE REQUIREMENTS
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• 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
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• 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
• Deficiencies lead to: • Weight loss• Skin lesions• Hormonal imbalances
LIPID SOURCES
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• 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
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• 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
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Heat
CO2+
+
+Energy
Fats from foods
Fatty acids
Ketone bodies
Beta oxidation
GlycerolGlucose Fat
Hydrolysis
Citricacidcycle
H2O
ATP
Acetyl coenzyme A
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Cholesterol Phospholipids
Fatty acids + Glycerol
Digestion
Triglycerides
Triglycerides Lipoproteins Fatty acids(except essential
fatty acids)
LIPID REQUIREMENTS
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• 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
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• 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• Deficiencies lead to:
• Extreme weight loss• Muscle wasting• Anemia• Growth retardation
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HormonesEnzymes
Proteins
Protein
Amino acids
Digestion
FatGlucose
Structuralproteins
Plasmaproteins
Energy + CO2 + H2O
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Heat
CO2+ +Energy
Proteins from foods
Amino acids
+
GlucoseFat
Urea
Hydrolysis
Deamination
–NH2 groupsDeaminated portions(by various pathways)
Acetylcoenzyme A
Citricacidcycle
H2O
ATP
PROTEIN SOURCES
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• 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
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• 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
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• 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
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18.5: ENERGY EXPENDITURES
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• Carbohydrates, fats and proteins supply energy for all metabolic processes• Deficiencies can lead to death• Excesses can lead to obesity
ENERGY VALUES OF FOOD
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• 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• 9.5 calories per gram
• Proteins• 4.1 calories per gram
Thermometer
Food sample
Insulation
Platinum dish
Stirrer
Oxygen
Electric wiresfor ignitionof sample
Water
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ENERGY REQUIREMENTS
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• 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
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• 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
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• 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
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Obesity
18.6: VITAMINS
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• 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)
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FAT-SOLUBLE VITAMINS
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• 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
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WATER-SOLUBLE VITAMINS
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• 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
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18.7: MINERALS
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• 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
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• 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
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TRACE ELEMENTS
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• 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
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18.8: HEALTHY EATING
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• 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
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MeatSweetsEggs
PoultryFish
Olive oilFruits
Fruits
The Mediterranean Diet Pyramid
Sweets
Fats
Carbohydrates
Protein/Dairy
Monthly
Monthly
Weekly
Daily
MeatsSweets
Eggs and poultry Weekly
Optional daily
Daily
Physical activity
GRAINS MILKFRUITS
OIL
S
ActivityActivity is represented by the steps and the person climbing them, as a reminder of the importance of daily physical activity.
ModerationModeration 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.
PersonalizationPersonalization is shown by the person on the steps and the slogan.
VEGE TABLES MEAT &BEANS
ProportionalityProportionality 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.
VarietyVariety 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 ImprovementGradual 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.govSTEPS TO A HEALTHIER YOU
U.S. Department of AgricultureCenter for Nutrition Policy and PromotionApril 2005 CNPP-16
Vegetables
Daily BeverageRecommendations: 6 glasses of water
Wine inmoderation
Cheese & Yogurt
Whole grains& potatoes
Daily Physical Activity
Beans, legumes& nuts
Vegetables
Fish and shell fishor 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 alcoholicbeverages and tea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
OliveOil
Mayo Clinic Healthy Weight Pyramid
OliveOil
MALNUTRITION
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• 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
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Dietary Supplements – Proceed With Caution
STARVATION
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• 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
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Nutrition and the Athlete
18.9: LIFESPAN CHANGES
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• 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
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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.
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Important Points in Chapter 18:Outcomes to be Assessed
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.
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Important Points in Chapter 18:Outcomes to be Assessed
18.9: Lifespan Changes
List the factors that may lead to inadequate nutrition later in life.