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Vitamins

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  1. Vitamins • Vitamins are essential for life • Vitamins are needed in small amounts • Vitamins do not provide energy • Vitamins have to be supplied by foods History 􀂄 Purified diets of carbohydrate, protein, fat, minerals and water were not capable of normal growth 􀂄 “Accessory growth factors” 􀂄 Casimir Funk, a Polish biochemist, isolated an antiberberi substance from rice polishings 􀂄 Named it vitamine 􀂄 An amine 􀂄 Vital for life

  2. Classification of Vitamins Classified according to solubility — Determines site in body were they function • Body tissues: watery or fatty (oily) — Fluids outside/inside body cells = waterbased — Cell membranes (layers)/nerve tissues = fatty substances • Vitamins that function in the watery areas = water-soluble vitamins • Vitamins that function in fatty tissues = fat-soluble vitamins

  3. Fat versus water soluble vitamins Fat-soluble vitamins • Dissolve in fat • Need fat: for absorption & transport • Can be stored in body: liver, adipose tissue Water-soluble vitamins • Dissolve in water • Are easily absorbed and excreted (via urine) • Are not easily stored

  4. Water soluble vitamins • B-group — B1 = thiamin — B2 = riboflavin — Niacin = nicotinamide = nicotinic acid = B3 — Pantothenic acid = B5 — B6 = pyridoxine — Biotin = vitamin B8 = vitamin H — Folic acid = folate = B11 — B12 = cobalamin ِ• Vitamin C = ascorbic acid Fat soluble vitamins • Vitamin A = retinol • Vitamin D3 = cholecalciferol • Vitamin E = α- tocopherol • Vitamin K1 = phylloquinone d

  5. Function • Essential for many processes in body • Vitamins play a role in digestion & utilization of — Protein — Fat — Carbohydrates • Vitamins are components of enzymes Some vitamins can be synthesised by body itself 􀃎 vitamin A• β-carotene — β-carotene = pro-vitamin A = vitamin A precursor (fore-runner) • From cholesterol 􀃎 vitamin D — In skin under influence of sunlight — Daily: 5-10 minutes • Bacterial flora in GI-tract 􀃎 vitamin K

  6. Vitamin A • Growth & repair of body tissues • Bone formation • Normal vision • Immune function • Deficiency: eye diseases leading to blindness

  7. Function of Vitamin D

  8. Vitamin A deficiency . 1. Impaired night vision (night blindness). 2. Dried skin, and mucous membranes fail to secrete mucus, causing: Drying and hardening of the cornea. 2) Severe – keratomalacia (total blindness) b) Drying and hardening of salivary glands, susceptible to infection, loss of appetite. c) Changes in GI tract lining, causing diarrhea. β-carotene is an antioxidant, which may decrease the risk of CVD and lung cancer.

  9. Vitamin D Vitamin D • Ca & P absorption / utilization: building bone mass & preventing bone loss • Skeletal integrity • Deficiency: rickets (malformation of bones) Vitamin D raises the blood concentration of Ca by: 1.Stimulating absorption of Ca and P from intestine (synthesis of calcium binding protein). 2.Withdrawing Ca from bones into blood for use in other parts of the body. 3.Stimulating Ca retention by kidneys.

  10. Vitamin D Deficiency Rickets (in children) Teeth: Slow eruption, not well formed, tendency to decay. Blood: Decreased Ca and/or P Bone: Poor calcification and retarded growth, deformities of ribs, enlargement of ends of long bones,, . Osteomalacia (in adults) Bone:Softening of bones, bone fracture, deformities of spine Blood: Decreased Ca and/or P levels ,

  11. Vitamin K Vitamin K is essential for synthesis of several proteins needed for blood coagulation or clotting. • Deficiency is rare: could be caused by conditions that interfere with absorption of fat or liver and gall bladder disease. • Deficiency results in “Hemorrhagic Disease”. • Vitamin K sources: – Made by intestinal bacteria – Food sources: green leafy vegetables, cabbage, milk, liver. 2-methyl-1,4-naphthoquinone structure phylloquinone (vitamin K 1 ) and menaquinones (vitamin K 2 ) Menadione, formerly known as vitamin K 3 Prolonged use of Sulfa drugs and antibiotic use may cause vitamin K deficiency.

  12. Vitamin K ,II,VII,X,XII

  13. Vitamin E The most active form of vitamin E, a-tocopherol, is a 6-hydroxychroman derivative.

  14. Vitamin E Vitamin E acts as an “antioxidant”. It protects vitamin A and polyunsaturated fatty acids from oxidation. • Antioxidant: compound that protects others from oxidation by being oxidize itself. – One of the most important organs where vitamin E exerts its antioxidant effect in lungs, where exposure to O2 is maximal, protects RBC and cells of lungs itself. – Vitamin E is also protective against strong oxidizing agents like ozone and nitrogen dioxide – air pollutants. These cause peroxidation of cell membrane lipids.

  15. Regulation of Vitamin C in the Body 􀂄 Absorption in small intestine via active transport 􀂄 Uses glucose transport protein 􀂄 High intakes 􀂄 Absorbed by simple diffusion in stomach & small intestine 􀂄 Circulates to liver via blood 􀂄 Excess excreted in urine Functions of Vitamin C 􀂄 Antioxidant 􀂄 Accepts & donates electrons 􀂄 Involved in a variety of redox reactions