Vitamins - Part 1 PDF

Vitamins Dr: Aseel M. Omran Introduction Vitamins are organic substances, not synthesized within the body, that are essential in small amounts for the maintenance of normal metabolic functions. They do not furnish energy and are not utilized as building units for cellula...

Vitamins Dr: Aseel M. Omran Introduction Vitamins are organic substances, not synthesized within the body, that are essential in small amounts for the maintenance of normal metabolic functions. They do not furnish energy and are not utilized as building units for cellular structure. The lack of specific vitamins leads to distinctive deficiency states such as beriberi, rickets, scurvy, and xerophthalmia, or to conditions without definitive symptoms. The term vitamin was derived in 1911 when an amine thought to prevent beriberi was isolated from rice bran; this essential or vital amine was called a vitamin. Not all vitamins are amines; vitamins A, C, D, E, K, and inositol lack a nitrogen function of any type. The vitamins are diverse chemically, ranging from a simple molecule such as niacin to a complex molecule such as cyanocobalamin. Vitamins are distributed widely and are normally ingested as constituents of various food substances. Fresh fruits, leafy vegetables, whole grains, eggs, and liver are rich dietary sources of vitamins. Vitamins obtained from natural sources and those prepared synthetically are in distinguishable biochemically, nutritionally, and therapeutically. Vitamins may be used as special dietary supplements or as drugs. Vitamin supplements are technically foods for special dietary needs and are unnecessary in most cases in which there is a balanced diet. Vitamins are considered drugs if they are taken to treat a condition of vitamin deficiency or to prevent imminent development of a disease. Vitamins can be classified into two classes: 1. fat soluble vitamin (A, D, E, K). 2. water soluble vitamins (C, B complex). Storage of vitamins: The fat soluble vitamins :- are stored in the body and their deficiencies are relatively rare. On the other hand, excessive intakes may be toxic. The water soluble vitamins :- are not stored to any significant extent in the body. Excess supplements of these vitamins are usually excreted in the urine. FAT-SOLUBLE VITAMINS Vitamins A, D. E, and K are fat soluble. Their absorption from the intestinal tract is associated with that of lipids, and a deficiency state may be caused by conditions that impair fat absorption. These conditions include pathologic situations such as biliary cirrhosis, cholecystitis, and sprue, and therapeutic situations such as cholestyramine regimens and excessive use of mineral oil laxatives. Vitamin A (Retinol) Vitamin A is a term applied to all derivatives of β -ionone, other than the carotenoids, Retinol is the major natural form of the vitamin, but known forms include the acetate and palmitate esters of the alcohol. Retinol is readily absorbed (80 to 90%) from the normal intestinal tract and is stored in body tissues, especially the liver. An estimated one third of the ingested vitamin A is stored under normal circumstances. Sources: - Fish liver oils are the natural sources of the vitamin and formerly were its primary commercial sources. - Common dietary sources of vitamin A are animal organs (heart, kidney, liver) - Vitamin A activity is also derived from some plant carotenoids that occur in carrots and green leafy vegetables. Only carotenoids that possess at least one unhydroxylated β -ionone ring (α-, β -, and -y-carotene and cryptoxanthin) can be converted to vitamin A. Beta-carotene and related carotenoids (provitamin A substances) are cleaved by β -carotene oxygenase in mucosal cells of the intestine to yield retinal, most of which is promptly reduced in the presence NADH to retinol. Uses of Vitamin A : 1.Vision 2.growth and development 3.Immune function 4. Red blood cell formation 5.Skin and bone formation. 6. Regulating gene transcription A deficiency of this vitamin can result in a variety of conditions including nyctalopia (night blindness), xerophthalmia, hyperkeratosis of the skin, growth retardation, and decreased resistance to infection. Xerophthalmia Nyctalopia hyperkeratosis Vitamin D  Vitamin D2 (ergocalciferol)  Vitamin D3 (cholecalciferol) Vitamin D is a term that is used for several related steroids and their metabolites that are essential for the absorption and utilization of calcium. The two forms of vitamin D differ depending on their food sources. Vitamin D3 is only found in animal-sourced foods, whereas D2 mainly comes from plant sources and fortified foods. Sources of Vitamin D3  Oily fish and fish oil  Liver  Egg yolk  Butter  Dietary supplements Sources of Vitamin D2  Mushrooms (grown in UV light)  Fortified foods  Dietary supplements Vitamin D has been called the sunshine vitamin since ultraviolet light is involved in the conversion of provitamin substances to vitamins D2 and D3. Vitamin D3 Is Formed in Your Skin Your skin makes vitamin D3 when it’s exposed to sunlight. Specifically, ultraviolet B (UVB) radiation from sunlight triggers the formation of vitamin D3 from the compound 7-dehydrocholesterol in skin. A similar process takes place in plants and mushrooms, where UVB light leads to the formation of vitamin D2 from ergosterol, a compound found in plant oils. If you regularly spend time outdoors, lightly clad and without sunscreen, you may be getting all the vitamin D you need. Uses of vitamin D :- 1.In the intestine assists in the absorption of calcium and phosphorus. 2.playing a role in bone and calcium homeostasis 3.Maintains muscle and nerve contraction 4.important for immune system function. 5.Maintains general cellular function in all cells of the body 6.use in cardiovascular disease, cancer , diabetes and multiple sclerosis. Deficiency states lead to rickets in children and osteomalacia in adults. Vitamin E (tocopherol) Vitamin E is a term that refers to various forms of α-tocopherol. Several structurally related tocopherol analogs also occur in nature, including B, y-, and S-tocopherols, but these substances possess only low levels of vitamin E activity. - Vitamin E is widely distributed in nature, and the body's requirements are normally satisfied by dietary sources. Dietary sources Plant oils, green vegetables, whole grains, egg yolks, and meats are common dietary sources of this vitamin. Wheat germ oil is a traditional natural source of vitamin E for therapeutic purposes. Uses of vitamin E Vitamin E is the major lipid-soluble antioxidant protects cell membranes, proteins, and DNA from oxidation and thereby contributes to cellular health. It prevents oxidation of the polyunsaturated fatty acids and lipids in the cells.  formation of blood vessels boosting of immune function Vitamin E deficiency can cause nerve and muscle damage that results in loss of feeling in the arms and legs, loss of body movement control, muscle weakness, and vision problems. Another sign of deficiency is a weakened immune system Vitamin K (naphthoquinone) Vitamin K1 (phytonadione, phylloquinone) Vitamin K2 (menaquinone) Vitamin K3 (Menadione) Vitamin K4 (Menadiol) Vitamin K is a term that refers to 2- methyl-1,4-naphthoquinone and derivatives of this compound. Sources: Vitamin K is distributed widely in dairy products and many fruits and vegetables, green leafy vegetables being especially good dietary sources. The intestinal microflora also provide a significant portion of the normal human supply of this vitamin. Uses of vitamin K Vitamin K acts primarily in blood clotting (antihemorrhagic activity) treatments for bleeding events caused by overdose of the anticoagulant drug warfarin  Helps in metabolism of bone proteins (osteocalcin) without vitamin K, osteocalcin cannot bind to the minerals that normally form bones, resulting in poor bone mineralization. regulation of blood calcium levels. deficiency : Hemorrhageis the most common symptom in vitamin K deficiency