Fat-Soluble Vitamins PDF

The fat-soluble vitamins: A, D, E and K Dr. Hadeel Alsufiani Chapter outline: The role in the body, deficiency, toxicity, recommendations and food sources of: Vitamin A Vitamin D Vitamin K Vitamin E  Vitamin A and Beta-Carotene Vitamin A was the first fat soluble vitami...

The fat-soluble vitamins: A, D, E and K Dr. Hadeel Alsufiani Chapter outline: The role in the body, deficiency, toxicity, recommendations and food sources of: Vitamin A Vitamin D Vitamin K Vitamin E  Vitamin A and Beta-Carotene Vitamin A was the first fat soluble vitamin to be recognized. The three different forms of vitamin A are active in the body: retinol, retinal and retinoic acid. Collectively known as retinoid, these compounds are commonly found in foods derived from animals. Foods derived from plants provide carotenoids, some of which can be converted to vitamin A. Conversion of vitamin A compounds Beta-carotene as a precursor and an antioxidant It serves as a vitamin A precursor Beta-carotene Some beta-carotene acts as an antioxidant  Vitamin A food sources Retinol Beta-Carotene pumpkin, deep fortified milk, cheese, orange fruits (apricots cream, butter, eggs, and cantaloupe) and liver and meat green leafy vegetables  Vitamin A recommendations Men: 900 microgram RAE/d Women: 700 microgram RAE/d Because the body can derive vitamin A from both retinoid and carotenoids, its content in foods and its recommendations are expressed as retinol activity equivalent (RAE) RAE: a measure of vitamin A activity; the amount of retinol that the body will derive from a food containing performed retinol or its precursor, beta-carotene. 1 microgram of retinol counts as 1 RAE, as does 12 micrograms of dietary beta- carotene. UL: 3000 microgram/d  Vitamin A deficiency Blindness Night blindness keratinization (xerophthalmia)  Vitamin A toxicity Bone Birth defects defects  Vitamin K Vitamin K appropriately gets its name from the danish word koagulation (‘coagulation” or “clotting”). its primary action is blood clotting, where its presence can make the difference between life and death.  Vitamin K food sources and recommendations Phylloquinone plant (K1) Vitamin K Bacteria and Menaquinone animal sources (K2) AI: for men 120 microgram/d and for women 90 microgram/d  Vitamin K deficiency Hemorrhagic disease: a disease characterized by excessive bleeding.  Vitamin K toxicity Toxicity is not common, and no adverse effects have been reported with high intakes of vitamin K. therefore, A UL has not been established.  Vitamin D (calciferol) Vitamin D differs from the other nutrients in that the body can synthesize it, with the help of sunlight, from a precursor that the body makes from cholesterol. Therefore, vitamin D is not an essential nutrient, given enough time in the sun, people need no vitamin D from foods.  Vitamin D comes in two major forms. Vitamin D2 ( ergocalciferol) derives primarily from plant foods in the diet. Vitamin D3 (cholecalciferol) (calciol) derives from animal foods in the diet and from synthesis in the skin. These two forms of are similar and both must be activated to 1,25-diOH- D3 before they can be fully function.  Roles in the body The overall function of 1,25-diOH-D3 is to maintain adequate plasma levels of calcium. It performs this function by: 1) increasing uptake of calcium by the intestine. 2) minimizing loss of calcium by the kidney by increasing reabsorption 3) stimulating resorption (demineralization) of bone when blood calcium is low.  Vitamin D food sources and recommendations Fatty fish (salmon and sardine), egg yolks, liver, fortified milk, margarines, butter, juices RDA for adults: 15 microgram/d (600 IU)  Vitamin D deficiency: Rickets Osteomalacia osteoporosis (in children) (in adults)  Vitamin D toxicity: Like all fat-soluble vitamins, vitamin D can be stored in the body and is only slowly metabolized. High doses (100,000 IUs for weeks or months) can cause loss of appetite, nausea, thirst. Enhanced calcium absorption and bone resorption results in hypercalcemia, which can lead to deposition of calcium in many organs, particularly the arteries and kidneys). The UL is 100 microgram/d (4000 IU/d). Vitamin E Vitamin E family tocopherols tocotrienols Alpha, beta, Alpha, beta, gamma and gamma and delta delta  Alpha-tocopherol is the most active form of Vitamin E. The others are not converted to alpha-tocopherol, nor are they recognized by its transport protein. For these reasons the RDA is based only on alpha- tocopherol.  Vitamin E as an antioxidant: Vitamin E is one of the body’s primary defenders against the adverse effects of free radicals. Its main action is to stop the chain reaction of free radicals from producing more free radicals. Most notably, vitamin E prevents the oxidation of the polyunsaturated fatty acids, but it protects other lipids. Vitamin E food sources and recommendations Polyunsaturated plant oils, dark green, leafy vegetables, egg yolks, nuts, seeds RDA for adults: 15 mg/d  Vitamin E deficiency A primary deficiency of vitamin E (from poor dietary intake) is rare, deficiency is usually associated with diseases of fat malabsorption. Without vitamin E, the red blood cells break and spill their contents, probably because of oxidation of the polyunsaturated fatty acids in their cell membrane. This classic sign of vitamin E deficiency, known as erythrocyte hemolysis, is seen in premature infants born before the transfer of vitamin E from the mother to the infants that takes place in the last weeks of pregnancy.  Vitamin E toxicity Vitamin E is the least toxic of the fat-soluble vitamins, and no toxicity has been observed at doses of 300 mg/d Extremely high doses of vitamin E may interfere with the blood-clotting action of vitamin K and enhance the effects of drug used to oppose blood clotting, causing hemorrhage.