Download Chapter 7

8
Nutrients Involved
in Energy
Metabolism
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Energy Metabolism
• Vitamins and minerals
• Do not directly provide energy
• Are needed for generating energy from
macronutrients
• B-complex vitamins are particularly important in
assisting energy metabolism
• Often function as coenzymes
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Energy Metabolism
• 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 in cell
regeneration and red blood cell synthesis
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Thiamin (vitamin B1)
• Coenzyme thiamin pyrophosphate is required
for metabolism of carbohydrate and branchedchain amino acids
• Assists in production of DNA and RNA and
synthesis of neurotransmitters
• Good sources: pork products, sunflower
seeds, beans, whole or enriched grains
• Deficiency (beriberi): muscle wasting, nerve
damage
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Riboflavin (Vitamin B2)
• Involved in oxidation−reduction reactions
• Part of coenzyme glutathione peroxidase
(antioxidant)
• Good sources: milk, enriched foods, meat
• Light sensitive (use opaque milk cartons)
• Ariboflavinosis: riboflavin deficiency; sore
throat, swollen mucous membranes
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Niacin (Vitamin B3)
• Two forms: nicotinic acid and nicotinamide
• Required for oxidation–reduction reactions of
carbohydrates, proteins, and fats
• Can be made from amino acid tryptophan
• Good sources: meat, fish, poultry, enriched
breads and cereals
• Toxicity symptoms from supplements
• Pellagra: severe niacin deficiency
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Vitamin B6 (Pyridoxine)
• Group of three related compounds
• Coenzyme in amino acid metabolism and
gluconeogenesis
• Good sources: meat, fish, poultry, enriched
cereals, starchy vegetables
• Toxicity from high-dose supplements: nerve
damage, skin lesions
• Deficiency involves skin, blood, nerve tissues
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Pantothenic Acid
• Essential for fatty acid metabolism
• Required for synthesizing cholesterol,
steroids, detoxification of drugs
• Good sources: chicken, beef, egg yolk,
potatoes, oat cereals, tomato products
• No adverse effects from excess amounts
• Deficiencies are very rare
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Biotin
• Coenzymes for fatty acid synthesis,
gluconeogenesis
• Carbohydrate, fat, and protein metabolism
• Content determined for very few foods
• Deficiency seen in large consumption of raw
egg whites over time
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Choline
• Vitamin-like substance: metabolism, cell
membranes, neurotransmission
• Fat and cholesterol metabolism/transport
• Homocysteine metabolism
• Widespread in foods
• Deficiency: fat accumulation in the liver
• Toxicity from excess supplementation
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Iodine
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Component of thyroid hormones
Regulates body temperature, metabolism
Important for reproduction and growth
Good sources: saltwater fish, iodized salt,
foods prepared with iodized salt
• Excess interferes with thyroid function
• Goiter: enlarged thyroid gland
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
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
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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
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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 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
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Manganese
• Cofactor in protein, fat, and carbohydrate
metabolism, gluconeogenesis, cholesterol
synthesis, and urea formation
• Part of antioxidant superoxide dismutase
• Good sources: whole-grain foods
• Toxicity impairs the nervous system, causing
spasms and tremors
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Sulfur
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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
© 2011 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
© 2011 Pearson Education, Inc.