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Chapter 24

Chapter 24 - Nutrition, Metabolism, and Body Temperature Regulation - Major Nutrients.doc

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Emily Agard

Nutrition, Metabolism, and Body Temperature Regulation Major Nutrients Kilocalorie (= calorie): amount of heat energy needed to raise the temperature of 1 kilogram of water 1 degree Celsius Diet & Nutrition Nutrient: substance in food the body uses to promote normal growth, maintenance, and repair Major nutrients: carbohydrates, lipids, proteins, water (not considered nutrient) - bulk amounts ‘Minor’ nutrients: vitamins, minerals – minute amounts Healthy Eating Pyramid = six major food groups, including subdivisions - Whole-grain foods - Fruits and vegetables - Vegetable oils instead of animal fats - Restrictions: red meat, sweets, starchy food MyPlate = food guide – USDA => healthy proportions Essential nutrients = cannot be made fast enough to meet the body’s needs, so our diet must provide them (45-50 molecules) – chemicals that must be obtained from outside sources Carbohydrates Dietary Sources - Carbohydrates => plants [except milk sugar & glycogen in meats] - Sugars => fruits, sugar cane, sugar beets, honey, milk - Polysaccharide starch => grains and vegetables - Fiber => o cellulose (not digested by humans, but = insoluble fiber => bulk of stool and facilitates defecation o soluble fiber = pectin (in apples/citrus fruits) = reduces blood cholesterol levels Uses in the Body - glucose => fuel by body cells to produce ATP - carbohydrate digestion => fructose & galactose <= liver converts them to glucose before they enter general circulation o neurons and red blood cells rely on glucose  lack of blood glucose = depress brain function => neuron death o excess glucose that is not needed for ATP synthesis = converted as glycogen/fat by the liver = later use - Fats = energy sources - *Meager = synthesize nucleic acids and a variety of sugars are attached to externally facing plasma membrane proteins/lipids Dietary Requirements - Can be healthy with a wide variations of carbohydrate intake - 100 g/day = maintain a normal/adequate blood glucose level - Dietary allowance: 130 g/day = amount needed to fuel the brain, not daily activities - 45-65% of total calorie intake - Less than 50 g/day = tissue/fat is used for energy fuel - “Empty calories” – concentrated energy sources – candy, soft drinks; > complex carbohydrates = nutritional deficiencies Lipids Dietary Sources - Abundant = triglycerides (= neutral fats) - Fats = digested => monoglycerides & fatty acids = triglycerides => lymph - Liver => 85% blood cholesterol o Convert one fatty acid => another o Cannot synthesize linoleic acid (fatty acid, component of lecithin)  Omega-6 fatty acid = ingested – ESSENTIAL  Linolenic acid = omega-3 fatty acid = ESSENTIAL  Vegetable oils contain these fatty acids Uses in the Body - Fats = full & satiated - Dietary fats = ESSENTIALS b/c o Helps the body absorb fat soluble vitamins o Triglycerides = energy fuel => hepatocytes & skeletal muscle o Phospholipids = integral component of myelin sheaths and cellular membranes o Fatty deposits in adipose tissue = (1) protective cushion around body organs, (2) insulating layer beneath the skin, (3) easy to store concentrated source of energy fuel o Prostaglandins: regulatory molecules formed from linoleic acid <= arachidonic acid  Role: smooth muscle contraction = control BP & inflammation Dietary Recommendations American Heart Association - Fat should be less than 30% intake - Saturated = less than 10% of total fat intake - Cholesterol intake = no more than 300 mg (amount in one egg yolk) - Blood cholesterol below 200 mg/
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