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Chapter 8 Lecture Chapter 8: Nutrients Involved in Energy Metabolism © 2017 Pearson Education, Inc. Energy Metabolism • Vitamins and minerals • Do not directly provide energy • Are needed for generating energy from macronutrients • Often function as coenzymes • B-vitamins are particularly important in assisting energy metabolism © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Energy Metabolism (cont.) • Coenzyme: a molecule that combines with an enzyme to activate it • Thiamin, riboflavin, vitamin B6, niacin, pantothenic acid, and biotin function primarily in energy metabolism • Folate and vitamin B12 function secondarily in cell regeneration and red blood cell synthesis © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Thiamin (Vitamin B1) • Coenzyme thiamin diphosphate is required for metabolism of glucose and branched-chain amino acids • Assists in production of DNA and RNA and synthesis of neurotransmitters • Food sources: pork products, sunflower seeds, beans, whole or enriched grains • Deficiency (beriberi): muscle wasting, nerve damage © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Riboflavin (Vitamin B2) • Involved in oxidation−reduction reactions within the electron transport chain • Part of coenzyme required by glutathione peroxidase to fight oxidative damage (antioxidant) • Food sources: milk, dairy, eggs, meat, broccoli, enriched grains and breads • Light sensitive (use opaque milk cartons) • Ariboflavinosis: riboflavin deficiency; sore throat, swollen mucous membranes © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Niacin (Vitamin B3) • Two forms: nicotinic acid and nicotinamide • Required for oxidation–reduction reactions of carbohydrates, proteins, and fats • Can be made in limited amounts from amino acid tryptophan • Food sources: meat, fish, poultry, enriched breads and cereals • Toxicity symptoms from supplements • Pellagra: severe niacin deficiency © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Vitamin B6 (Pyridoxine) • Group of three related compounds • Roles include: • Amino acid and carbohydrate metabolism • Gluconeogenesis • Neurotransmitter and heme synthesis • Immune function • Metabolism of niacin, folate and carnitine • Reduction in cardiovascular disease © 2017 Pearson Education, Inc. Vitamins: Vitamin B6 (Pyridoxine) (cont.) • Food sources: meat, fish (tuna), poultry, enriched cereals, starchy vegetables • Toxicity from high-dose supplements: nerve damage, skin lesions • Deficiency affects skin, blood, nerve tissues (anemia, convulsions, depression, and confusion) © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Folate • Works with enzymes • These enzymes are critical for DNA synthesis, cell differentiation, amino acid metabolism • Synthesis of new cells and repair of damaged cells • Plays a special role in embryo development • Deficiency issues include neural tube defects in infants, anemia, and heart disease • Food sources include green leafy vegetables, bread and grain products (fortified), liver, lentils, asparagus, and oatmeal. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Vitamin B12 (Cyanocobalamin) • Includes a number of compounds that have a cobalt center surrounded by a ring structure • Works with coenzymes to assist DNA synthesis for the formation of red blood cells • Essential for nervous system functioning • Food sources are animal and non-plant products; meat, eggs, dairy, and seafood • Absorption is complex and requires intrinsic factor • Deficiencies are rare; associated with anemia © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Pantothenic Acid • Essential for fatty acid metabolism • Required for synthesizing cholesterol, steroids, detoxification of drugs • Food sources: chicken, beef, egg yolk, potatoes, oat cereals, tomato products, certain mushrooms • No adverse effects from excess amounts • Deficiencies are rare © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Biotin • A component of coenzymes used for fatty acid synthesis, gluconeogenesis • Also contributes to carbohydrate, fat, and protein metabolism • Content had been determined for very few foods • Deficiencies are seen in large consumption of raw egg whites over time, and in people who must consume food intravenously © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Vitamins: Choline • Vitamin-like substance: metabolism, cell membranes, neurotransmission (acetylcholine) • Fat and cholesterol metabolism/transport • Homocysteine metabolism • Widespread in foods • Deficiency: fat accumulation in the liver • Toxicity from excess supplementation © 2017 Pearson Education, Inc. Minerals: Iodine • • • • Component of thyroid hormones Regulates body temperature, metabolism Important for reproduction and growth Food sources: saltwater fish, iodized salt, foods prepared with iodized salt • Excess interferes with thyroid function • Goiter (enlarged thyroid gland) occurs with both toxicity and deficiency © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Minerals: Iodine • Iodine deficiency disorders (IDDs) • Cretinism: mental retardation, stunted growth • Hypothyroidism: low thyroid hormone results in decreased body temperature, cold intolerance, weight gain, fatigue, sluggishness © 2017 Pearson Education, Inc. Minerals: Iodine • Hyperthyroidism: high levels of thyroid hormone caused by Graves' disease • Weight loss, increased heat production, muscular tremors, nervousness, racing heartbeat, and protrusion of the eyes © 2017 Pearson Education, Inc. Minerals: Chromium • Assists insulin to transport glucose from the bloodstream into the cells • Important for RNA and DNA metabolism • Supports immune function and growth • Dietary adequacy is controversial • Widely distributed in foods • High-dose supplementation safety is unknown • Deficiency induced in labs: inhibit glucose uptake into the cells, causing a rise in blood glucose and insulin levels © 2017 Pearson Education, Inc. Minerals: Manganese • A cofactor in protein, fat, and carbohydrate metabolism, gluconeogenesis, cholesterol synthesis, and urea formation • Part of antioxidant enzyme superoxide dismutase • Food sources: whole-grain foods • Toxicity impairs the nervous system, causing spasms and tremors © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Minerals: Sulfur • • • • • • • A major mineral Component of thiamin and biotin Part of amino acids: methionine, cysteine Required by liver for alcohol detoxification Assists in maintaining acid–base balance Obtained from dietary proteins No known toxicity or deficiency symptoms © 2017 Pearson Education, Inc. Inadequate B-Vitamin Intake • Impacts ability to perform physical activity • Limited studies show poor work performance: lower intensity and duration • Diets high in unenriched processed foods provide inadequate levels of B-vitamins • Some B-vitamins lost in milling of grains are replaced by the enrichment process © 2017 Pearson Education, Inc.