Vitamins and Minerals - Student Notes PDF

VITAMINS AND MINERALS COMPILED AND ARRANGED BY JUSTIN RACHELLE P. DIMAGUIBA  Learning outcomes Identify the classification, uses, and application to nursing care Describe biochemical and physiological functions of vitamins and minerals.  Vitamins organic co...

VITAMINS AND MINERALS COMPILED AND ARRANGED BY JUSTIN RACHELLE P. DIMAGUIBA  Learning outcomes Identify the classification, uses, and application to nursing care Describe biochemical and physiological functions of vitamins and minerals.  Vitamins organic compounds, essential in small amounts for the proper functioning of the human body must be obtained from dietary sources because the body cannot synthesize it Organic compounds occurring in natural foods either as such or as utilizable precursors, which are required in minute amounts for normal growth, maintenance and reproduction, i.e. for normal nutrition and health.  Vitamins Certain vitamins and minerals are needed for the body to function. 13 vitamins 22 minerals Two types of vitamins Water-soluble Fat-soluble  13 Essential Vitamins Vitamin A helps form and maintains healthy teeth, bones, soft tissue, mucous membranes, and skin. Vitamin B6 helps break down proteins, helps maintain normal nerve function and form red blood cells. Vitamin B12 is essential for metabolism. It also helps form red blood cells and maintains the central nervous system. Vitamin C promotes the health of teeth and gums as well as wound healing.  13 Essential Vitamins Vitamin D helps the body absorb calcium, which is important for healthy teeth and bones. It also helps maintain proper blood levels of calcium and phosphorus. Vitamin E is an antioxidant that plays a role in the formation of red blood cells. Vitamin K is required for normal coagulation of the blood. Some studies suggest that it helps maintain bone health in the elderly.  13 Essential Vitamins Biotin is essential for the metabolism of proteins and carbohydrates, and in the production of hormones and cholesterol. Niacin helps maintain healthy skin and nerves. It also has cholesterol-lowering effects. Folate works with vitamin B12 to help form red blood cells. It is also necessary for the production of DNA which controls tissue growth and cell function.  13 Essential Vitamins Pantothenic acid is essential for the metabolism of food. It is also plays a role in the production of hormones and cholesterol. Riboflavin (B2) works with the other B vitamins. It is important for body growth and the production of red blood cells. Thiamine (B1) helps the body’s cells change carbohydrates into energy. It is also essential for heart function and healthy nerve cells.  Fat-Soluble vitamins Vitamin A, D, E and K Excess is stored in the liver and in body fat It is possible to build up to a toxic level Vitamin A (Retinol) — Beta-carotene is converted into vitamin A — Vitamin A: ◦ Promotes good vision ◦ Promotes healthy skin ◦ Helps with growth and maintenance of bones, teeth, and cell structure — RDA: 900 micrograms for males; 700 micrograms for females Too much vitamin A May turn your skin orange May cause fatigue, weakness, severe headache, blurred vision, hair loss and joint pain. Toxicity: May cause severe liver or brain damage Birth defects Vitamin A analogues Isotretinoin and etretinate are used to treat skin disorders. Isotretinoin is used to treat severe acne (but must be avoided in pregnancy, causing birth defects). Etretinate was used to treat psoriasis but it has been withdrawn in some countries. Too little vitamin A May cause night blindness Lowered immune system  Foods rich in vitamin A Foods Only animal products Liver Eggs Milk, butter and Carotenoids cheese Orange/Yellow fruits and vegetables Cantaloupes, carrots, sweet potatoes, winter squash Leafy green vegetables Spinach, broccoli  Vitamin D “The Sunshine Vitamin” Essential for building and maintaining bones and teeth Responsible for absorption and utilization of calcium Other health benefits: May boost immune system May also help decrease certain cancers RDA: 5 micrograms until age 50 10 micrograms / day until 70; 15 mcg 70+  Vitamin D “The Sunshine Vitamin” Ergosterol, the plant equivalent of cholesterol, is converted to vitamin D2 by ultraviolet light. Vitamin D3 (cholecalciferol) is formed in the skin from 7- dehydrocholesterol (an intermediate in the cholesterol biosynthesis pathway) in the presence of ultraviolet light, which opens the B-ring of the steroid nucleus.  Vitamin D “The Sunshine Vitamin” Cholecalciferol is successively hydroxylated first in the liver forming 25- hydroxycholecalciferol (25- HCC) and then in the kidney to form the most active form: 1,25- dihydroxycholecalciferol (1,25-DHCC), also known as calcitriol. Too little vitamin D Rickets in children Osteoporosis in adults Deficiency may occur from: Inadequate diet lactose intolerance, milk allergy Malabsorption- Steatorrhoea caused by exocrine pancreatic disease or biliary obstruction can cause vitamin D deficiency. Limited exposure to sunlight  Vitamin D Deficiency May lead to osteomalacia and/or osteoporosis Vitamin D toxicity Hypervitaminosis D produces hypercalcaemia that can result in bone loss, organ calcification (e.g. kidneys and heart) and kidney stones. Vitamin D hypersensitivity in sarcoidosis - extrarenal 1α-hydroxylase activity occurs in sarcoid granulomas, which converts vitamin D to inappropriately high concentrations of 1,25-DHCC, causing hypercalcaemia. Also occurs in some lymphomas and sarcomas.  Sun exposure for 10 minutes a day Foods: Fortified milk Tuna Salmon May need a supplement Check with doctor first though  Vitamin E four tocopherols (α-, β-, γ- and δ-) and four tocotrienols (α-, β-, γand δ-). Of these, α-tocopherol is the most important  Vitamin E BIOCHEMICAL FUNCTION α-tocopherol is an antioxidant that prevents free radical damage to polyunsaturated fatty acids, particularly those in the cell membrane of red blood cells. Evidence suggests α-tocopherol reduces oxidative damage to low density lipoproteins (LDLs), which is associated with the development of atherosclerosis. 500 IU α-tocopherol/day claim inhibition of lipid oxidation in atherosclerotic lesions  Vitamin E Important to red blood cells, muscles and other tissues Deficiency is rare Toxicity is rare But Vitamin E acts as a blood thinner Foods: Vegetable oils, salad dressings, whole grain cereals, green leafy vegetables, nuts, seeds, peanut butter and wheat germ.  Vitamin E Diagnostic test for deficiency Measure platelet vitamin E concentration Dietary sources Vegetable oils, nuts and green leafy vegetables Deficiency diseases occurs in children with cystic fibrosis and patients with steatorrhoea. Red cell membrane damage results in haemolytic anaemia. Damage to nerve cells causes peripheral neuropathy. Toxicity high doses might cause increased clotting times in subjects with a low vitamin K status  Vitamin K From the Danish word coagulation exists in two natural forms: vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). Vitamin K3 (menadione) is a synthetic, water-soluble analogue Vitamin K Important for blood clotting Also has a role for bone health Mostly made in the intestines Foods: Turnip greens, cauliflower, spinach, liver, broccoli, kale and cabbage  Vitamin K Biochemical function 1. Blood clotting -precursors of the anticoagulants prothrombin and factors VIII, IX and X are activated when glutamate (Glu) residues are carboxylated to γ- carboxyglutamate (Gla) by a vitamin K-dependent reaction. This process is linked to regeneration of vitamin K in the “vitamin K epoxide cycle”  Vitamin K Biochemical function 2. Bone mineralization. - suggests that vitamin K plays a role in bone growth and development.  Vitamin K Diagnostic test for deficiency Measure under carboxylated Gla proteins in the blood. Dietary sources The major source is phylloquinone (vitamin K1) found in vegetable oils and green leafy vegetables. Menaquinone (vitamin K2) is synthesized by the flora of the large intestine.  Vitamin K deficiency Hemorrhagic disease of the newborn Placental transfer of vitamin K is inefficient so deficiency can occur, resulting in neonatal hemorrhage. Breast milk a poor source of vitamin K. Osteoporosis an association between osteoporotic fracture and vitamin K.  Vitamin K toxicity intravenous menadione causes oxidative damage to red cell membranes (haemolysis) Water-Soluble Vitamins  Thiamin Pyrophosphate (Vit. B1) essential for pyruvate dehydrogenase and similar large multienzyme complexes which oxidatively decarboxylate a-ketoacids. RNI 0.4 mg/1000 kcal (depends on energy intake)  Vitamin B1 Biochemical function a) Cofactor for pyruvate dehydrogenase in the “link reaction” between glycolysis and Krebs cycle. Involved in energy metabolism from glucose and other carbohydrates b) Cofactor for a-ketoglutarate dehydrogenase c) Cofactor for several a-ketoacid dehydrogenases, e.g. the branched-chain a-ketoacid dehydrogenases involved in amino acid oxidation d) Cofactor for transketolase in the pentose phosphate pathway  Thiamin Pyrophosphate (Vit. B1) Helps to convert carbohydrates to energy Deficiency: Fatigue, nausea, depression, nerve damage Foods: Pork, beef, liver, peas, seeds, legumes, whole-grain products, and oatmeal  Thiamin Pyrophosphate (Vit. B1) Diagnostic test Hyperlactatemia especially after a glucose load when pyruvate and lactate (which are immediately upstream of pyruvate dehydrogenase) accumulate. Measurement of red blood cell transketolase activity in the absence and presence of additional thiamin (ETKAC) Dietary sources cereals, pulses, yeast, liver Vitamin B1 deficiency and toxicity (a) Associated with alcohol abuse causing Wernicke’s encephalopathy and Korsakoff’s dementia (b) Wet beriberi: edema, cardiovascular disease; and Dry beriberi: neuropathy and muscle wasting (c) Toxicity: 3 g/day (variety of clinical signs)  Riboflavin or Vit. B2 involved in energy metabolism from glucose and fatty acids. a component of FAD which is the prosthetic group of several enzymes used in oxidation/reduction reactions. a component of FMN which is in complex I of the respiratory chain  Vitamin B2 Biochemical function (a) Needed for the multi-enzyme complexes involved in oxidative decarboxylation (i) Cofactor for pyruvate dehydrogenase in the “link reaction” between glycolysis and Krebs cycle. Cofactor for a-ketoglutarate dehydrogenase (ii) Cofactor for several a-ketoacid dehydrogenases, e.g. the branched-chain a-ketoacid dehydrogenases involved in amino acid oxidation (b) Prosthetic group for succinate dehydrogenase in Krebs cycle (c) A constituent of FMN which is a component of complex I in the respiratory chain (d) Cofactor for acyl CoA dehydrogenase in b-oxidation  Riboflavin or Vit. B2 Key to metabolism and red blood cells Deficiency: Dry, scaly skin Foods: Milk, yogurt, cheese, whole-grain breads, green leafy vegetables, meat, and eggs  Riboflavin or Vit. B2 Diagnostic tests: (a) Measure activity of red blood cell glutathione reductase which is a FAD-dependent enzyme (b) Measure urinary secretion of riboflavin Dietary sources: - Milk, liver, yeast, eggs. Present in fortified cereal products but poor in natural cereals Toxicity: - No evidence of toxicity Deficiency diseases: (a)Inflamed, magenta-coloured tongue. (b)Ultraviolet light destroys riboflavin and so neonates given phototherapy for jaundice need riboflavin supplements Pantothenate or Vit. B5 important as a component of coenzyme A which has numerous functions in carbohydrate, lipid and amino acid metabolism Daily requirement 4–7 mg Vitamin B5 Biochemical function a component of coenzyme A (CoASH) which has numerous functions in carbohydrate, lipid and amino acid metabolism also a component of the acyl carrier protein used in fatty acid synthesis  Pantothenate or Vit. B5 Diagnostic test -Measure blood concentration Dietary sources - ubiquitous, present in all foods Toxicity - 0 - none up to 10 g/day Deficiency diseases - apart from the infamous “burning feet syndrome” seen in prisoners of war, deficiency conditions have not been described  Pyridoxal phosphate or Vit. B6 is needed for several reactions of the amino acids, notably transamination. also needed for phosphorylase (glycogen breakdown), the biosynthesis of vitamin B3 (NAD+) from tryptophan, and the catabolism of homocysteine. RNI 1.5 mg/day Toxic in high doses Vitamin B6 Biochemical function pyridoxal phosphate is essential for aminotransferase (transamination) reactions in amino acid metabolism needed both for biosynthesis of the non- essential amino acids and also for amino acid oxidation for energy metabolism Also an important component of glycogen phosphorylase  Pyridoxal phosphate or Vit. B6 Diagnostic tests Measure plasma concentration of B6 - Measure urinary excretion of xanthurenate (yellow product) following an oral load of tryptophan. Normally tryptophan catabolism proceeds via the B6- dependent kynureninase but in B6 deficiency, xanthurenate accumulates Dietary sources meat, fish, milk and nuts - NB: Pyridoxal phosphate deficiency also compromises the synthesis of NAD+ etc. from tryptophan Deficiency most common in alcoholism. Inflammation of tongue, lip and mouth  Cobalamin or B12 Helps with nervous system, red blood cells and DNA synthesis Deficiency: Nervous system disorders and pernicious anemia a significant problem, especially in vegetarians and particularly in vegans. Foods: Only found in animal products Meat, fish, poultry, eggs, milk products and clams Vitamin B12 Biochemical function Vitamin B12 (cobalamin) has two active forms that are involved in two reactions: 1. Methylcobalamin is needed for methionine synthase (also known as homocysteine methyltransferase) for the methionine salvage pathway. 2. Deoxyadenosylcobalamin is needed for the methylmalonyl CoA mutase reaction.  Cobalamin or Vitamin B12 Diagnostic tests 1. Full blood count and mean cell volume. 2. Measure plasma concentration of cobalamin. 3. Schilling test: radiolabelled vitamin B12 is given and urinary excretion is measured. Less than 10% B12 excretion suggests deficiency. Pernicious anaemia is confirmed by repeating with intrinsic factor if the excretion of B12 is normalised to >10% of the dose. 4. Measure methylmalonic acid in the urine. Vitamin B12 deficiency 1. B12 deficiency causes deficient methionine synthase activity, which results in megaloblastic anemia similar to folate deficiency. In pernicious anemia the parietal cells of the stomach are destroyed by autoimmune attack and are unable to produce intrinsic factor (50 kDa glycoprotein), which is needed for the absorption of cobalamin in the ileum. 2. B12 deficiency causes homocysteinaemia, which is associated with cardiovascular disease. 3. A deficiency of methylmalonyl CoA mutase causes accumulation of methylmalonyl CoA. It is thought that this competes with the normal precursor malonyl CoA for lipid synthesis.  Folic acid (Folacin, Folate- B9) Serine, tryptophan and histidine donate 1-carbon units to folate metabolites that are used for DNA and RNA synthesis during cell division and growth. NB: Vitamin B12 is needed for the metabolism and function of folate.  Folic acid (Folacin, Folate- B9) Key role in red blood cell formation and cell division Deficiency: Anemia, digestive disorders Foods: Leafy, dark green vegetables Also found in liver, beans, peas, asparagus, oranges, avocados  Vitamin B9 Biochemical function 1. Measure plasma/serum folate or red cell folate. 2. Haematology tests for megaloblastic anemia. 3. Measure FIGLU (N-formiminoglutamate) after a loading dose of histidine.  Folic acid or Vitamin B9 Dietary sources Green leafy vegetables (Latin folium, leaf) and also yeast are sources. Deficiency diseases 1. Folate is needed for cells undergoing rapid division and growth, e.g. haemopoietic tissue in bone marrow. Deficiency causes megaloblastic anemia. 2. Moderate folate deficiency at the time of conception is associated with neural tube defects, e.g. spina bifida. It is recommended that women who may conceive should take folate supplements of 400 µg daily. 3. Deficiency is associated with hyper homocysteinemia, which is a risk factor for cardiovascular disease.  Niacin or B3 a component of the hydrogen carriers, NAD+ and NADP+ Both have numerous roles in metabolism but NAD+ is especially important as a “hydrogen carrier” for ATP production by the respiratory chain, whereas NADPH is very important for biosynthetic reactions. Daily requirement: 6.6 niacin equivalents/1000 kcal  Vitamin B3 Biochemical function niacin is a term for nicotinic acid & nicotinamide. A component of NAD+ and NADP+, and their reduced forms, NADH and NADPH which are involved in numerous metabolic reactions. NAD+ is involved in glycolysis, the oxidation of fatty acids, amino acid oxidation and Krebs cycle. It is particularly important as a “hydrogen carrier” since oxidation of NADH by the respiratory chain generates ATP. NADP+ and its reduced form NADPH+ are particularly important in biosynthetic reactions, e.g. lipid synthesis.  Vitamin B3 Biochemical function Dietary sources vitamin -enriched breakfast cereals, liver, yeast, meat, pulses. Approximately half the daily requirement can be biosynthesized from tryptophan (60 mg of tryptophan - 1 mg niacin) Deficiency diseases pellagra (from the Italian “rough skin”) occurs if diet is deficient in BOTH niacin and tryptophan such as maize-based diets (dermatitis, diarrhoea, dementia) Pharmacology/toxicity pharmacological doses (of 2–4 g daily) have been used in trials as a hypolipidaemic agent Excessive nicotinic acid can cause transient vasodilation with hypotension  Niacin or B3 Also involved with energy production Also helps with skin, nerves and digestive system Deficiency: Rare but causes: diarrhea, dermatitis, dementia and death Foods: Meat, poultry, liver, eggs, brown rice, baked potatoes, fish, milk, and whole-grain foods  Ascorbic acid or Vitamin C — needed for several hydroxylation reactions notably prolyl- and lysylhydroxylase in the formation of collagen — Also important as a free radical scavenger — Requirements 50 – 60 mg daily  Vitamin C Biochemical functions (a) Hydroxylation of proline and lysine which is needed for cross-linking in structure of collagen (b) Functions as a free radical scavenger preventing oxidative damage, e.g. to lipids in cell membranes and LDL (low density lipoproteins); to proteins and to DNA which may cause mutations leading to cancer. (c) Saves vitamin E from oxidative damage (d) Needed for the biosynthesis of carnitine, noradrenaline. Also needed by the microsomal cytochrome P450 enzymes which are involved in the metabolism of drugs and toxic substances.  Ascorbic acid or Vitamin C Diagnostic tests Measure vitamin C in white blood cells (“buffy coat”) Dietary sources Fresh fruit, particularly citrus fruits, and vegetables Deficiency Impaired synthesis of collagen leads to scurvy characterized by bleeding gums, bruising and poor wound-healing. Vitamin C supplements improve wound-healing and decrease skin- bruising in some types of Ehlers–Danlos syndrome.  Ascorbic acid or Vitamin C — Important to bone health, blood vessel health, cell structure and absorption of iron — Deficiency: ◦ scurvy — Too much vitamin C — Foods: ◦ Melons, berries, tomatoes, potatoes, broccoli, fortified juices, kiwi, mangos, yellow peppers and citrus fruits  Minerals Two categories: Major/Macrominerals Include calcium, chloride, magnesium, phosphorus, potassium, sodium, and sulfur Trace/Microminerals Include iron, zinc, iodine, selenium, copper, manganese, fluoride, chromium, molybdenum, arsenic, nickel, silicon, boron and cobalt End of presentation