Vitamins PDF

VITAMINS CLASSIFICATION OF VITAMINS FAT SOLUBLE VITAMINS Vitamin A Is Derived from Plant Carotenoids The active forms of vitamin A are Retinol, Retinal and Retinoic acid  The most important Carotenoids It is essential for the synthesis of glycoproteins n...

VITAMINS CLASSIFICATION OF VITAMINS FAT SOLUBLE VITAMINS Vitamin A Is Derived from Plant Carotenoids The active forms of vitamin A are Retinol, Retinal and Retinoic acid  The most important Carotenoids It is essential for the synthesis of glycoproteins needed for normal growth regulation and mucus secretion and its deregulation leads to drying of epithelial tissues Regulation of cell growth. It downregulates synthesis of Keratin and deficiency leads to hyperkeratosis and are required for Iron transport protein transferrin synthesis and deficiency leads to anemia Deficiency leads to increased susceptibility to infection and cancer FAT SOLUBLE VITAMINS Vitamin D synthesis requires sunlight Clinical indications Nutritional rickets: Vitamin D deficiency causes a net demineralization of bone, resulting in rickets in children and osteomalacia in adults. Rickets is characterized by the continued formation of the collagen matrix of bone, but incomplete mineralization, resulting in soft, pliable bones. In osteomalacia, demineralization of bones increases their susceptibility to fracture. Insufficient exposure to daylight and/or deficiencies in vitamin D consumption occur predominantly in infants and the elderly. Vitamin E is a very important naturally occurring antioxidant The term vitamin E refers to a family of 8 related compounds -tocopherol is the most active.  Vitamin E is a very important naturally occurring antioxidant Tocopherol is the most potent scavenger of reactive oxygen species (ROS) Tocopherol is a more potent scavenger of reactive nitrogen species (RNS). Stabilizing ATP production in the cells Prevent atherosclerosis Tocopherol increases the levels enzymes involved in heme synthesis Maintaining normal immune function Neurological symptoms have been reported following prolonged vitamin E deficiency The signs of human vitamin E deficiency include sensitivity of erythrocytes to undergo membrane rupture and other cellular membranes. Vitamin K is a Quinone derivative The γ-carboxyglutamic acid residues are good chelator (complex maker) that allow the proteins to bind Ca2+ Clinical indications Deficiency of vitamin K: A true vitamin K deficiency is unusual because adequate amounts are generally produced by intestinal bacteria or obtained from the diet. If the bacterial population in the gut is decreased, for example, by antibiotics, the amount of endogenously formed vitamin is depressed, and this can lead to hypoprothrombinemia. This condition may require supplementation with vitamin K Deficiency of vitamin K in the newborn: Newborns have sterile intestines and so initially lack the bacteria that synthesize vitamin K. Because human milk provides only about one fifth of the daily requirement for vitamin K, it is recommended that all newborns receive a single intramuscular dose of vitamin K as prophylaxis against hemorrhagic disease. WATER SOLUBLE VITAMINS  WATER SOLUBLE VITAMINS Excreted once their concentration are high, so toxicities are rare Their metabolic stores are labile and deficiencies occur relatively quickly on an inadequate diet. Most water-soluble vitamins are converted to coenzymes that are used in pathways for energy generation or hematopoiesis. Deficiencies of the energy-releasing vitamins produce a number of overlapping symptoms and show up first in rapidly growing tissues. Thiamin (B1) Significant sources Whole grain, fortified, or enriched grain products Moderate amounts in all nutritious food Pork Easily destroyed by heat Thiamin (B1) Forms the Coenzyme Thiamin Pyrophosphate A coenzyme required for activity on enzymes which are involved in bioenergetics Symptoms of mild thiamin deficiency include loss of appetite, constipation, nausea, mental depression, peripheral neuropathy, irritability, and fatigue. Symptoms of moderately severe thiamin deficiency are mental confusion, ataxia and ophthalmoplegia (Wernicke Korsakoff syndrome). Severe thiamin deficiency is known as Beriberi (neuromuscular symptoms, including muscular atrophy and weakness) Riboflavin (B2) Significant sources Milk products (yogurt, cheese) Enriched or whole grains Liver Easily destroyed by ultraviolet light and irradiation Riboflavin (B2) Forms the Coenzymes FAD and FMN coenzyme Riboflavin is the required for coenzymes (FAD and FMN ) in a wide variety of redox reactions. Riboflavin is also required for iron mobilization, and riboflavin deficiency can contribute to anemia when iron intake is low. Characteristic symptoms of riboflavin deficiency are angular cheilitis, glossitis, and scaly dermatitis Foods rich in riboflavin include milk, meat, eggs, and cereal products. Riboflavin deficiencies are quite rare and are common in chronic alcoholics.  Chief functions in the body Niacin (B3) Part of coenzymes NAD (nicotinamide adenine dinucleotide) and NADP (its phosphate form) used in energy metabolism Significant sources Milk, eggs, meat, poultry, fish Whole-grain and enriched breads and cereals Nuts All protein-containing foods Precursor: dietary tryptophan Upper level for adults: 35 mg/day  Niacin (B3) Forms the Coenzymes NAD and NADP NAD is also required tor the poly-ADP-ribose polymerase reaction, which regulates DNA replication, DNA repair, and cell cycle progression. Niacin deficiency results in a glossitis (redness) of the tongue, pellagra, which is characterized by the three Ds: dermatitis, diarrhea, and dementia. The neurologic symptoms are associated with actual degeneration of nervous tissue. Pregnancy, lactation, and chronic illness lead to increased needs for niacin, but a varied diet usually provides sufficient amounts. The richest sources of niacin are meats, peanuts and other legumes, and enriched cereals. Pyridoxine (B6) Other names Pyridoxine Pyridoxal Pyridoxamine As coenzyme for Transamination Deamination Decarboxylation Condensation reactions Pyridoxine (B6) Deficiency leads to poor activity of PLP-dependent enzymes Causing: Deficient amino acid metabolism Deficient lipid metabolism Deficient neurotransmitter synthesis: Serotonin, epinephrine, norepinephrine and gamma amino butyric acid (GABA) PLP is involved in the synthesis of sphingolipids Its deficiency leads to demyelination of nerves and consequent peripheral neuritis Mild deficiency leads to: Irritability Nervousness Depression Severe deficiency leads to: Peripheral neuropathy Convulsions Biotin (B7) Chief functions in the body Part of a coenzyme used in energy metabolism, fat synthesis, amino acid metabolism, and glycogen synthesis Significant sources Widespread in foods Organ meats, egg yolks, soybeans, fish, whole grains Also produced by GI bacteria Deficiency symptoms Depression, lethargy, hallucinations, numb or tingling sensation in the arms and legs Red, scaly rash around the eyes, nose, and mouth Hair loss Toxicity symptoms: none reported Pantothenic Acid (B5) Chief functions in the body Part of coenzyme A, used in energy metabolism CoA in produced form B5 Significant sources Widespread in foods Organ meats, mushrooms, avocados, broccoli, whole grains Easily destroyed by food processing Deficiency symptoms Vomiting, nausea, stomach cramps Insomnia, fatigue, depression, irritability, restlessness, apathy Hypoglycemia, increased sensitivity to insulin Toxicity symptoms: none reported Folate (B9) Main function of tetrahydropholate transfer a single carbon atom including the methyl group–CH3 from compound to compound. FOLIC ACID DEFICIENCY Folic acid deficiency can be due to poor diet, chronic alcoholism, inadequate absorption (e.g. damage to the upper third of small intestine), use of drugs such as anticonvulsants, or extra demand during pregnancy or lactation. An intracellular deficiency of folic acid can also arise if methionine synthesis is impaired. Folic acid deficiency results in anaemia. This is known as megaloblastic anaemia, since it results in the formation of large, abnormal forms of the cells that are precursors for erythrocytes. This is because erythrocyte development arrests at this stage due to lack of purine and pyrimidine nucleotides for DNA synthesis. Anaemia is characterised by weakness, tiredness, irritability, headache and palpitations.  Folate Deficiency symptoms Anemia (large-cell type) Smooth, red tongue Mental confusion, weakness, fatigue, irritability, headache Toxicity symptoms Masks vitamin B12-deficiency symptoms Neural tube defects Spina bifida Vitamin B12 (Cobalamin) Cobalamin (B12) Two reactions require B12 Conversion of methylmalonyl- CoA to succinyl-CoA by methyl-malonyl-CoA mutase Methionine synthase reaction Homocystein to Methionine B12 Deficiency symptoms Pernicious anemia Megaloblastic anemia Myelin sheath of neurons is chemically unstable and damaged Neuropathy Peripheral nerve damage Causes of neuropathy Deficiency of vitamin B12 leads to accumulation of methylmalonyl CoA High levels of methylomalonyl CoA is used instead of malonyl CoA for fatty acid synthesis Myelin synthesized with these abnormal fatty acids is unstable and degraded causing neuropathy  OTHER WATER-SOLUBLE VITAMINS VITAMIN C Vitamin C or ascorbic acid is a cofactor for mixed function oxidases involved in the hydroxylation of Lys and Pro, synthesis of carnitine, synthesis of norepinephrine, absorption of iron by reducing it to the ferrous state in the stomach Hydroxylation of Proline and Lysine is catalized by peptidyl hydroxylases; prolyl hydroxylase and lysyl hydroxylase Deficiency of vitamin C required for hydroxylase results in scurvy in which bleeding gums, swelling joins and impaired wound healing results from the impaired stability of collagen C vitamin Deficiency Capillary fragility Scurvy Decreased wound healing osteoporosis, hemorrahaging and anemia Since C vitamin is required for normal leukocyte function and for histamine level decrease, it is recommended for prevention of cold. Smoking causes lower C vitamin levels.