Fat-Soluble Vitamins

Chapter

10

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© Photodisc

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 © Digital Stock

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 © Photodisc

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 calcium-binding properties.