Fat-Soluble Vitamins Overview

Fat-Soluble Vitamins

• Vitamins A, D, E, and K are fat-soluble.
• These vitamins are essential for health, needed in small amounts.
• They are absorbed and used by the body.
• Vitamins dissolve in fat and are stored in fat tissues.

Vitamins in general

• Vitamins are essential nutrients in small amounts to prevent deficiency diseases and support health.
• Bioavailability is the rate and extent of a nutrient's absorption and use.
• Precursors (provitamins) are inactive forms of vitamins that become active in the human body.
• Cooking and storage can destroy vitamins.

Water-Soluble vs. Fat-Soluble Vitamins (Comparison)

Vitamin A

• Vitamin A exists in the body as retinoids: retinol, retinal, and retinoic acid.
• Sources include retinyl esters in animal foods and beta-carotene in plant foods.
• Functions include maintaining the cornea, converting light to nerve impulses in the retina (using rhodopsin), and regulating growth.
• Deficiency can lead to night blindness, impaired immunity (children), and xerophthalmia (blindness).
• A build-up can cause bone defects and birth defects, and acute toxicity includes nausea, vomiting and headaches.
• RDA for men is 900 µg RAE/day and for women 700 µg RAE/day

Vitamin D

• Other names include calciferol, 1,25-dihydroxy vitamin D (calcitriol).
• Animal sources: vitamin D₃ (cholecalciferol); Plant sources: vitamin D₂ (ergocalciferol).
• Cholesterol is a precursor.
• Exposure to sunlight produces vitamin D3 in the skin.
• Functions include maintaining blood calcium and phosphorus levels (through reabsorption from the digestive tract, mobilization from bones, and stimulating retention by kidneys).
• Deficiency can cause rickets in children (bowed legs, and enlarged ends of long bones, deformed ribs) and osteomalacia in adults (soft and deformed bones).
• Symptoms include progressive weakness and pain in pelvis, lower back, and legs.
• AI for 19-50 years: 5 µg/day, for 51-70 years: 10 µg/day, and for more than 70 years: 15 µg/day.
• Significant sources include fortified milk, margarine, butter, cereals, chocolate mixes, beef, egg yolks, liver, fatty fish (like salmon and sardines).

Vitamin E

• Four tocopherol compounds; only alpha-tocopherol is active.
• Functions as an antioxidant, stopping free radical chain reactions, protecting LDL oxidation, and protecting polyunsaturated fatty acids and Vitamin A.
• Deficiency is rare, but can cause loss of muscle coordination, impaired vision, speech problems, and nerve damage.
• Toxicity is uncommon.
• RDA for adults is 15 mg/day; upper level is 1000 mg/day.
• Excellent sources include polyunsaturated plant oils, salad dressings, leafy green vegetables, wheat germ, whole grains, liver, egg yolks, nuts, and seeds.

Vitamin K

• Functions include synthesizing blood-clotting proteins and bone proteins to regulate blood calcium.
• Deficiency symptoms include hemorrhaging and hemorrhagic disease.
• Newborn infants usually receive a single dose of Vitamin K at birth because their intestinal tracts are initially sterile.
• Secondary deficiencies may occur with antibiotic use.
• Toxicity is rare and there are no known toxicities.
• RDA for men is 120 µg/day and for women 90 µg/day.
• Sources include liver, leafy green vegetables and cabbage-type vegetables, and milk.

This quiz explores fat-soluble vitamins A, D, E, and K, highlighting their importance for health, absorption, and storage in the body. Understand the differences between water-soluble and fat-soluble vitamins, their characteristics, and how they interact with the body. Test your knowledge on vitamins and their vital roles in nutrition.