Vitamins PDF

VITAMINS DR AJAEGBU OBINNA. MBBS, MSC, FMCPAED. Introduction They are substances that are essential for normal metabolism. Human cannot synthesize vitamins in the body except some vit D. Deficiency of vitamin could be primary (inadequate dietary intake) or secondary (failure of absorption or incre...

VITAMINS DR AJAEGBU OBINNA. MBBS, MSC, FMCPAED. Introduction They are substances that are essential for normal metabolism. Human cannot synthesize vitamins in the body except some vit D. Deficiency of vitamin could be primary (inadequate dietary intake) or secondary (failure of absorption or increase metabolism). Vitamins are classified as 1. Water soluble---- vitamin B group and vitamin c 2. Fat soluble---- vitamin A,D, E, K 1. Vitamin A: Retinol  Vitamin A is a generic term embracing substances having the biological action of retinol and related substances (called retinoid).  It is a fat soluble vitamin, bile is necessary for its absorption and it is stored in the liver  Principal action of retinol are: 1. Sustain normal epithelia 2. Promote cornea and conjunctiva development 3. Enhance immune function 4. Form retinal photochemical  Sources of vitamin A: Liver, dairy products, green vegetables, yellow fruits.  Deficiency of vitamin A:  Xeropthalmia, Photophobia, bitot spots, conjunctivitis, blindness  Squamaous cell metaplasia  Hyperkeratosis  Impairment of immune function Effects of excess vitamin A  Anorexia  Drying and cracking of skin  Swelling and pain of long bones  Increased intracranial pressure  alopecia Therapeutic uses of vitamin A  Tazorotene, a topical retinoid, is effective in the treatment of chronic plaque psoriasis.  Tretinon is retinoic acid and is useful in treatment of acne.  Tretinoin can be used to induce remission in conjunction with chemotherapy in acute promyelocytic leukemia. 2a. Vitamin B1 (Thiamine)  It is a water soluble vitamin. It a component of thiamine pyrophosphate involved in oxidative decarboxylation of alpha-keto acids such as pyruvates.  Thiamine pyrophosphate is a cofactor involved in the citric acid cycle.  Deficiency of thiamine leads to impaired production of glutamic acid and GABA which are neurotransmitters.  Sources: Meat, whole-grain eg legumes, nut.  Deficiency usually occur following impaired intake or from chronic alcoholism.  Deficiency of Vitamin B1 leads to the following. 1. Wernicke encephalopathy (opthalmoplegia, ataxia, confusion) 2. Korsakoff syndrome (amnesia, deficit in explicit memory, confabulation) 3. Beri-beri. 2b. Vitamin B2  A member of the flavoprotein enzymes important in oxidation- reduction reaction. It is a water soluble vitamin  Sources: milk, chees, meat, vegetables, egg etc  Deficiency:  Ariboflavinosis;  angular stomatitis,  glossitis,  photophobia,  blurred vision,  burning and itching eyes,  poor growth 2c.Vitamin B3 (Niacine)  Niacine is converted to nicotinamide and subsequently to nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADPH); the co-factors that are essential for the oxidation-reduction reactions that comprise tissue respiration.  Sources: meat, fish, poultry  Deficiency of niacin is called pellagra. (dermatitis, diarrhea and dementia)  Deficiency occurs following reduced intake eg Tryptophan;  other causes include alcoholism, carcinoid syndrome and Hartnup disease, chronic inflammatory bowel syndrome. 2d. Vitamin B6 (pyridoxine)  It a co-enzyme in the metabolism of many amino acids, including decarboxylation and transamination.  Sources: meat, fish, fortified cereals  Deficiency of vitamin B6 includes, microcytic anaemia, dermatitis, cheilosis, impaired immune function  Pyridoxine is given to treat certain pyridoxine-dependent inborn errors of metabolism eg homocystenuria, herediatary sideroblastic anaemia and primary hyperoxaluria.  Deficiency can be induced by drugs such as isoniazid, hydralazine, penicillin. 2e. Vitamin B12  The cobalamins are a family of compounds that have vitamin B12 activity. They have same basic structures with cobalt within a central corin ring.  Vitamin B12 is required by all cell for DNA synthesis; it is also required for red cell production, methylation and myelin synthesis.  Vitamin b12 is only produced by microorganism and human obtain it by ingesting foods of animal origin.  Sources: animal foods: meat, fish.  Ingested vitamin b12 binds to intrinsic factor (IF) synthesized by gastric parietal cells. The cobalamine-intrinsic factor complex passes to the terminal ileum where it is absorbed.  Newly absorbed vitamin b12 binds to transcobalamin to form holotranscobalamin (20-30% of plasma vitamin b12); this is the biologically active form which is available for delivery to cell. The remaining (70%) is bound to haptocorrin which is taken up and stored in the liver. Causes of vitamin b12 deficiency 1. Inadequate dietary intake: elderly and vegans 2. Pernicious anaemia: autoimmune destruction of the gastric parietal cells produce atrophic gastric mucosa and reduced secretion of intrinsic factors. Deficiency results from failure to absorb cobalamine in the terminal ileum. 3. Mal-absorption syndromes: intestinal disease affecting the terminal ileum can interrupt the normal enterohepatic circulation of vitamin b12. eg gastrostomy, gastric bypass surgery, tropical sprue 4. Drugs. Eg metformin, phenytoin, large doses of vit c can reduce vit b12 absorption 5. Congenital defect: Transcobalamin deficiency enzyme defects. 6. Deficiency leads to megaloblastic anemia. 2e. Folic acid  Folic acid is one of the B group vitamins and is widely distribute particularly in green vegetables, fruits, yeast and liver. It is water soluble.  Absorbed in the proximal jejeunum following deconjugation to the monoglutamate form. In the plasma it is present as 5-methy tetrahydroflate. Causes of deficiency of folic acid 1. Inadequate dietary intake: 2. Mal-absrption syndrome: jejunum resection, Gluten-sensitive enteroathy. 3. Increased folate requirement: prematurity, pregnancy, dialysis, psoriasis. 4. Antifolate drugs: long term antiepileptic use (phenytoin, phenobabitone), methotrexate, trimetroprim, pyrimethamineally. Deficiency of folic acid  Deficiency of folic acid causes megaloblastic anemia as a result of impaired production of purines and pyrimidines, essential for DNA synthesis. 3. Vitamin C: ascorbic acid  Vitamin C is a powerful reducing agent (antioxidant) and is an essential cofactor and substrate in a number of enzymatic reaction  Deficiency of ascorbic acid leads to scurvy which is characterize by petechial hemorrhages, hematomas, bleeding gums and anaemia.  Ascorbic acid is useful in treatment of methaemoglobinaemia. Ascorbic acid is needed to convert the metaemoglobin (ferric iron) back to oxyhaemoglobin (ferrous iron) when there is impairment of oxygen carrying capacity of the blood. Methylene blue (Methylthioninium chloride) is another alternative that can be used. 4. Vitamin D  Vitamin D comprises of a number of structurally related sterol compounds having similar biological properties in that they are useful in prevention/treatment of vitamin D-deficiency diseases, rickets and osteomalcia. It is a fat soluble vitamin.  Types 1. Vitamin D2: ergocalciferol: produced by ultraviolent irradiation of ergosterol in plant. Not the naturally occurring form. 2. Vitamin D3: colecalciferol: this is made by ultraviolent irradiation of 7-dehydrocholesterol in the skin.  Vitamin D3 undergoes successive hydroxylations: first in the liver to form 25-hydroxyvitamin D3 and second in the proximal tubules of the kidney (under the control of parathyroid hormone t form 1,25dihydroxyvitamin D.  Action :Vitamin D promotes the active transportation of calcium and phosphate in the gut (increase absorption) and renal tubules (reduced excretion).  Deficiency: Rickets in growing children, osteomalacia, hypocalcaemia  Sources: exposure to sunlight, fish oil, egg yolks Indication of vitamin D use  Treatments/ prevention of rickets and osteomalacia  Osteoporosis  Hypoparathyroidism  Psoriasis  Renal osteodystophy (CKD) 5. Vitamin E  They are group of compounds with similar biologic activities; with alpha tocopherol the most potent and common form. It is fat soluble  Action: it is a good antioxidant necessary in protection of cell membranes from lipid peroxidation and formation of free radicals  Sources: vegetable oils, seeds, nuts, green leafy vegetables.  Deficiency: red cell hemolysis in infants; posterior column and cerebella dysfunction; pigmentary retinopathy. 6. Vitamin K  They are group of napthoquinones with similar biologic activities  K1 (phylloquinone) from diet  K2 (menaquinones) from intestinal bacteria  They are fat soluble, stable to heat and re reducing agents.  Action: They are essentials in synthesis of vitamin K dependent clotting factors like factors II, VII, IX, X.  Sources: green leafy vegetables, liver, legumes.  Deficiency: Hemorrhage. Summary.  Vitamins are essential component of the body needed for proper growth and development.  Deficiency of vitamins could be primary or secondary.  Deficiency may manifest as mild symptoms or serious symptoms depending on level of deficiency.  Early identification and prompt management is key. In the presence of the Lord there is fullness of joy, in his right hand are pleasures for evermore. Psalm 16:11