Chapter
10 Fat-Soluble Vitamins
Understanding Vitamins • A few myths… • If a little is good, then a lot is better. • Vitamins are energy boosters. • Vitamins work exclusively of one another.
• Vitamins in foods • Natural sources: all food groups • Enriched and fortified foods
Understanding Vitamins • Anatomy of the Vitamins • • • •
Daily needs are small Not an energy source Individual units Organic compounds essential for normal functioning, growth, and maintenance • Functions often interrelated
Fat-Soluble Versus Water-Soluble Vitamins • Fat-soluble • Vitamins A, D, E, and K
• Water-soluble • B vitamins and vitamin C
Understanding Vitamins • Fat-soluble • Vitamins A, D, E, and K • Absorbed like fat, into lymphatic system • Stored in larger quantities, therefore, toxicities may occur • May have precursors • Less vulnerable to cooking losses
Understanding Vitamins • Water-soluble • • • •
Eight B-vitamins and vitamin C Absorbed into bloodstream Stored in small amounts Vulnerable to cooking losses
Vitamin Absorption
Understanding Vitamins • Storage and Toxicity • Fat-soluble • Accumulate in the liver and adipose tissue
• Water-soluble • Not stored in appreciable amounts
Understanding Vitamins • Provitamins • Vitamins in food
Vitamin A: The Retinoids • Forms • Retinoids • Carotenoids • Provitamin A
Vitamin A: The Retinoids • Storage and Transport • Functions • • • •
Vision Cell Differentiation Reproduction Bone Health
Vitamin A: The Retinoids • Dietary Recommendations
Vitamin A: The Retinoids • Sources • Proformed Vitamin A • Dietary Vitamin A • Provitamin A • Caroteniods
Vitamin A • Deficiency • Eyes, skin, other epithelial tissues, immune function
• Toxicity • Can be fatal! • Acne treatment
Carotenoids • Functions • • • • •
Source of vitamin A Fighting free radicals (antioxidants) Immune system Vision Cancer
Carotenoids • Absorption and Storage of Carotenoids • Food Sources • Yellow-orange vegetables • Orange fruits • Dark-green leafy vegetables
• Supplementation
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Vitamin D • Forms and Formation • Made in the skin from cholesterol • Activated in liver and kidney
• Functions • Regulates blood calcium levels
• Dietary recommendations • Sources • Sunlight • Dietary sources
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Vitamin D • Deficiency • Rickets in children • Osteomalacia and osteoporosis in adults • Other conditions • Who is most at risk?
• Toxicity • Hypercalcemia
Vitamin E • Forms • Tocopherol, tocotrienals
• Functions • Antioxidant • Protects cell membranes from free radicals
Vitamin E • Dietary recommendations • Food sources • Nuts and seeds • Wheat germ • Oils, margarine, salad dressing
• Deficiency • Hemolysis
• Toxicity is rare
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Vitamin K • Functions • Blood clotting • Formation of bone
• Dietary recommendations • Food sources • Green vegetables, liver, egg yolks
Vitamin K • Deficiency • Rare in healthy people • Increases risk of hemorrhage
• Toxicity • Can interfere with anticoagulant medications • Toxicity is rare
Vitamins: An Overview • All types of foods contain vitamins. Provitamins are vitamin precursors that the body can convert to the active vitamin form. Growing conditions, storage, processing, and cooking all affect the amounts of vitamins in foods. • For at the last 3,000 years, there has been an empirical understanding that some diseases (which we now call vitamin deficiency diseases) could be cured by eating certain foods.
Mucous Membrane Integrity • Mucous membranes contain a higher percentage of goblet cells. • With retinoic acid, fewer stem cells become goblet cells and these surfaces become hard and scaly.
Vitamin A and Vision • Deficiency of vitamin A results in progressive vision loss from temporary night blindness, then reversible blindness, and finally permanent blindness. • In addition, the lack of mucous secretions and reduced immune function make the person with vitamin A deficiency vulnerable to infections. Vitamin A toxicity can result from the use of supplements, even with dosages just a few times higher than the RDA.
Osteoporosis • A lack of vitamin D can lead to osteoporosis. • Vitamin D supplements in elderly women slows bone turnover, increases bone density, and decreases nonvertebral fractures.
Free Radical Damage • Vitamin E helps prevent free radical damage to polyunsaturated fatty acids in cell membranes.
Vitamin K and Bone Health • Osteocalcin is an abundant bone protein that is required for bone mineralization and maturation. • Vitamin K helps in the carboxylation of osteocalcin, greatly enhancing its calciumbinding properties.