Chapter 18Nutrition and Metabolism

Nutrients –

Macronutrients• • •

Micronutrients• vitamins• minerals

Essential Nutrients•

• synthesize• certain amino acids

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Carbohydrates

Sources• • starches• • glycogen in meats

RDA is 125-175g

Excesses lead to • • dental• nutritional deficits

Deficiencies lead to • metabolic acidosis•

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Utilization of Carbohydrates

• • production of certain molecules (ribose, deoxyribose)• stored as glycogen• converted to fats and stored in adipose tissue

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Utilization of Carbohydrates

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Lipids

Sources• • eggs• • lard• plant oils

RDA is 80-100g

Excesses lead to • • increased serum cholesterol•

Deficiencies lead to • • skin lesions• hormonal imbalances

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Utilization of Lipids

• • production of triglycerides, phospholipids, lipoproteins, and cholesterol• • glycerol may be used to synthesize glycerol

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Utilization of Lipids

The liver uses fatty acids to synthesize a variety of lipids.

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Proteins

Sources• • cheeses• • legumes

RDA is 0.8g/kg body weight or 10% of diet

Excesses lead to obesity

Deficiencies lead to • • muscle wasting• anemia• growth retardation

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Utilization of Proteins

• • enzymes• • transport of oxygen• regulation of water balance• control of pH• formation of antibodies• can be converted to carbohydrates or fats• may be broken down and oxidized for energy

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Nitrogen Balance

• 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

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Energy Values of Food

Carbohydrates4.1 calories per gram

Lipids9.5 calories per

gram

Proteins4.1 calories per gram

Calorie –

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Energy Requirements

Basal metabolic rate • • primarily reflects energy needed to support activities of organs• varies with gender, body size, body temperature, and endocrine function

Energy needed • • to support muscular activity• to maintain body temperature• for growth in children and pregnant women 18-16

Energy Balance

• • positive energy balance leads to weight gain

• overweight is defined as exceeding desirable weight by 10% - 20%• obesity occurs when person is 20% above desired weight due to excess adipose tissue

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Fat Soluble Vitamins

Vitamin A• synthesized from carotenes• stored in liver• necessary for visual pigments• necessary for bone and teeth development• necessary for maintenance of epithelial cells• excesses lead to nausea, headache, dizziness, hair loss, birth defects• deficiencies lead to night blindness and degeneration of epithelial tissues

Vitamin D• group of steroids• stored in liver, brain, skin, spleen, and bone• promotes absorption of calcium and phosphorus• necessary for bone and teeth development• excesses lead to diarrhea, calcification of soft tissues, and renal damage• deficiencies lead to bone weakening

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Fat-Soluble Vitamins

Vitamin E• stored in muscles and adipose tissue• prevents oxidation of vitamin A and some fatty acids• may help stability of cell membranes• excesses lead to hypertension

Vitamin K• stored in liver• necessary for prothrombin synthesis• deficiencies lead to bruising and bleeding

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Sources of Fat-Soluble Vitamins

Vitamin A• liver • fish• milk• leafy green vegetables• yellow and orange vegetables and fruits

Vitamin D• skin • egg yolk• milk• fish liver oils

Vitamin E• cereal seed oils• salad oils• margarine• shortening• fruits• nuts• vegetables

Vitamin K• liver • soy oil• egg yolk• leafy green vegetables• tomatoes• cauliflower 18-20

Water-Soluble Vitamins

Vitamin B1

• thiamine•coenzyme for carbohydrate oxidation• meats• liver• leafy green vegetables• eggs• cereals• legumes• deficiencies lead to Beriberi, muscular weakness, enlargement of heart

Vitamin B2

• riboflavin• parts of enzymes and coenzymes (FAD)• milk• leafy green vegetables• meats• deficiencies lead to dermatitis and blurred vision

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Water-Soluble Vitamins

Niacin• parts of coenzymes (NAD)• liver• meats• peanuts• legumes• deficiencies lead to pellagra, dermatitis, diarrhea, or mental disorders

Pantothenic Acid• part of coenzyme A• meats• cereals• legumes• milk• vegetables • deficiencies lead to mental depression and muscle spasms

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Water-Soluble Vitamins

Vitamin B6

• part of coenzymes needed for synthesis of proteins• meats• cereals• peanuts• milk• bananas• avocados• deficiencies lead to vomiting and convulsions

Vitamin B12

• part of coenzyme needed for nucleic acid synthesis• plays role in myelin sheath formation• needed for RBC formation• meats• milk• liver• cheese• eggs• deficiencies lead to anemia

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Water-Soluble Vitamins

Folic Acid• coenzyme required for amino acid and nucleic acid metabolism• needed for normal RBC production• cereals• legumes• milk• leafy green vegetables • deficiencies lead to anemia

Biotin• coenzyme required for metabolism of amino acids, fatty acids, and nucleic acids• egg yolk• liver• legumes• nuts• mushrooms• deficiencies lead to elevated blood cholesterol, fatigue, nausea, and anorexia

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Water-Soluble Vitamins

Vitamin C• ascorbic acid• needed for collagen production and metabolism of some amino acids• promotes absorption of iron and synthesis of hormones from cholesterol• citrus fruits• tomatoes• potatoes• leafy green vegetables • deficiencies lead to scurvy, lowered resistance, and slow wound healing 18-25

Minerals

Major Minerals• calcium• phosphorus• potassium• sulfur• sodium• chlorine• magnesium

Trace Elements• iron• manganese• copper• iodine• cobalt• zinc• fluorine• selenium• chromium

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Major Minerals

Calcium• mostly in bones and teeth• needed for bone structure• essential for nerve impulse conduction• essential for muscle fiber contraction• essential for blood coagulation• increases permeability of cell membranes• activates certain enzymes• excesses lead to kidney stones• deficiencies lead to stunted growth and fragile bones

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Major Minerals

Phosphorus• mostly in bones and teeth• needed for structure of bones and teeth• component in nearly all metabolic processes• constituent of ATP, nucleic acids, many proteins, enzymes, and some vitamins• deficiency leads to stunted growth

Potassium• widely distributed• maintains intracellular osmotic pressure and pH• promotes metabolism• required for muscle contraction and nerve impulse conduction• deficiency leads to muscular weakness, cardiac abnormalities, and edema

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Major Minerals

Sulfur• widely distributed• abundant in skin, nails, and hair• component of certain amino acids, thiamine, biotin, and mucopolysaccharides

Sodium• widely distributed• maintains osmotic pressure of extracellular fluids• regulates water movement in and out of cells• required for nerve impulse conduction and contraction of muscle fibers•excesses lead to edema and hypertension• deficiency leads to muscle cramps and convulsions 18-29

Major Minerals

Chlorine• most concentrated in cerebrospinal fluid and gastric juice• helps maintain osmotic pressure of extracellular fluids• regulates pH• essential for formation of hydrochloric acid• aids in transport of carbon dioxide•deficiency leads to muscle cramps

Magnesium• abundant in bones• required in metabolic reactions for ATP production• helps breakdown of ATP to ADP• excess leads to diarrhea• deficiency leads to neuromuscular disturbances

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Trace Elements

Iron• part of hemoglobin• catalyzes formation of vitamin A• incorporated into some enzymes

Manganese• occurs in enzymes required for fatty acid and cholesterol synthesis, formation of urea, and functioning of the nervous system

Copper• essential for hemoglobin synthesis, bone development, melanin production and myelin formation 18-31

Trace Elements

Iodine• component of thyroid hormone

Cobalt• required for synthesis of several enzymes

Zinc• component of many enzymes• necessary for wound healing and maintaining integrity of skin

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Trace Elements

Fluorine• component of tooth structure

Selenium• occurs in enzymes

Chromium• essential for use of carbohydrates

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Food Pyramid

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Malnutrition

• poor nutrition • undernutrition – • overnutrition – • primary malnutrition – malnutrition from diet alone• secondary malnutrition – diet is sufficient but nutrients cannot be absorbed

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Starvation

• person can survive 50-70 days without food• symptoms include low blood pressure, slow pulse, chills, dry skin, hair loss, and poor immunity•Anorexia nervosa – • Bulimia –

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Life-Span Changes

• BMR rises in early childhood and peaks in adolescence • BMR declines in adulthood• change in nutrition often reflects effects of medical conditions and social and economic circumstances

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