Second stage Animal nutrition /vitamins dr. Ahmed Qassem Khalaf. Vitamins

Transcription

1 Vitamins The discovery of the first vitamin was published in 1911 by a Polish biochemist, Casimir Funk. The term vitamine is derived from the words vita (meaning lifegiving) and amine (were originally thought to be amines). Although not all vitamins are amines, they are organic compounds required by humans in small amounts from the diet. Usually only a few milligrams (mg) or micrograms (μg) are needed per day, but these amounts are essential for health. Most vitamins cannot be made by the body, so have to be provided by the diet. An exception is vitamin D which can be obtained by the action of sunlight on the skin. Small amounts of a B vitamin (niacin) can be made from the essential amino acid, tryptophan. Vitamin K is formed by bacterial action in the large intestine. Vitamins functions Vitamins do not contain energy, but they help regulate energy process in the body. Vitamins have a variety of functions in the body: some are co-factors in enzyme activity, some are antioxidants (prevent oxygen from doing damage in the body) and one (vitamin D) is a prohormone. If insufficient amounts of vitamins are available to the body because of a poor diet or some medical condition (e.g. malabsorption of nutrients), specific symptoms will appear and can develop into a deficiency disease. Vitamin deficiency diseases are rare in the westernized society, but still occur in some parts of the world. Vitamins and minerals are measured in milligrams (mg), micrograms (µg) and international units vitamins requirements The body requires different amounts of each vitamin because each of them has a different function. People have different requirements too, according to their age, gender, level of activity and state of health. Vitamin supplements Although most people are able to meet their requirements for vitamins by eating a varied diet, there are certain groups of the population who have higher than normal requirements, e.g. the sick, those taking certain drugs and pregnant women. Infants and young children are recommended to have supplements of vitamins A and D for at least 2 years.

2 Some women many require additional vitamins if menstrual losses are high. The evidence for benefits from antioxidant supplementation for athletes is mixed. Vitamin classification Vitamins have been traditionally grouped into two categories: 1. the fat soluble vitamin (A, D, E, K), 2. the water soluble vitamins (C, B complex). riginally, vitamins were given letters (A, B, C, etc.) but now are usually referred to by their chemical names, e.g. folate. The fat soluble vitamins are stored in the body and their deficiencies are relatively rare. n 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. The water soluble vitamins 1-Vitamin C (Ascorbic acid ) Vitamin C is the most famous vitamin. sources: almost exclusively in foods from plant sources (citrus fruits, broccoli, peppers, kiwi, strawberries, potatoes, tomatoes), although fresh milk and liver contain small amounts. RDA: 80 mg one kiwi, small orange or 4 strawberries provides 100% of RDA Structure Metabolism 1. oxidation/reduction 2. dehydroascorbic acid 3. dehydroascorbate reductase 4. glutathione (GSH)

3 Major function in the body glutamate-cysteine-glycine 1. helps form collagen 2. helps in growth and repair of body tissue and blood vessels 3. prevents scurvy 4. a strong antioxidant 5. aids in absorption of iron 6. helps regulate the metabolism of cholesterol and amino acids 7. Enhances absorption of iron 8. reduces iron to more absorbable ferrous form 9. chalets with ferrous ion to make it more soluble Hydroxylation Reactions Synthesis of Neurotransmitters Dopamine Norepinephrine Serotonin Bile acid synthesis Antioxidant Activity 1. Reacts and removes active oxygen species 2. Pro-oxidant Activity 3. Reduces metals to their pro-oxidant forms RDA for Vitamin C mg/day prevents scurvy 2. historic RDA s mg (60mg in 1989), 75mg in prevention of scurvy vs antioxidant effect with supplements? Anti-oxidant properties of vitamin C: 1. Normal metabolic processes in the cell lead to the generation 2. of reactive oxidizing agents such as superoxide 3. Superoxide can react with and damage protein and DNA, leading 4. to cellular changes that can lead to premature aging and cancer

4 5. Vitamin C reacts with superoxide, thus preventing this damage H H H H H H Ascorbic acid deficiency scurvy 1. hemorrhage from mucous membranes, mouth and GIT, skin and muscles 2. gingivitis: swelling, tenderness, redness bleeding and ulceration of gums 3. Petechiae 4. easy bruising 5. impaired wound healing and bone repair 6. loosening or loss of teeth 7. swelling of joints 8. rarefaction of bones and dentine 9. anemia The vitamin can be decreased by cigarette smoking, stressful injuries, stress and oral contraceptives. hypervitaminosis: excessive doses can cause kidney stones and break down red blood cells Toxicity of Vitamin C 1. UL adults: 2000mg/d 2. smotic diarrhea 3. xalate kidney stones 4. Decreases uric acid reabsorption resulting in increased risk of gout 2-VITAMIN B CMPLEX Eight vitamins that make up the B Complex of vitamins: 1. Vitamin B 1 (Thiamine)

5 2. Vitamin B 2 (Riboflavin) 3. Vitamin B 3 or Vitamin P or Vitamin PP (Niacin) 4. Vitamin B 5 (Pantothenic acid) 5. Vitamin B 6 (Pyridoxine and Pyridoxamine) 6. Vitamin B 7 or Vitamin H (Biotin) 7. Vitamin B 9 or Vitamin M and Vitamin B-c (Folic acid) 8. Vitamin B 12 (Cyanocobalamin) 2-Thiamin (Vitamin B1) Structure pyrimidine ring thiazole ring methyl bridge Pyrimidine ring Thiazole ring sources: whole grains, nuts and meat. White and brown flour and many breakfast cereals are usually fortified with thiamin. RDA: 1,5 mg for men, 1,1 mg for women function: Thiamin is needed to release energy from carbohydrate. It is involved in the normal function of the nervous system and the heart. Vitamin B1 deficiency causes beri-beri (symptoms: weight loss, emotional disturbances, weakness and pain in the limbs, irregular heart rate...), a disorder of the nervous system, which occurs in communities where white rice is the main food eaten. A different type of thiamin deficiency affecting brain function is sometimes seen in alcoholics, where daily thiamin intake is low and absorption and utilisation of the vitamin is impaired.

6 hypervitaminosis: general lack of toxicity Chemical Characteristics 1. Very labile nutrient 2. Heat a) stable in crystalline form b) less stable in solution 3. Alkali - very unstable with heat baking soda 4. Sulfites - decomposes B-1 High cooking/processing losse Absorption of B-1 1. in duodenum 2. active transport (low thiamin levels) requires sodium and folic acid 3. passive transport (hi B-1 levels) 4. phosphorylation to active form inside cells (TPP) 5. transported via portal blood 6. no significant storage, excess to urine Thiamin Deficiency 1. Beri-Beri 2. anorexia, fatigue, depression 3. effects on a) cardiovascular system b) nervous system in animals Polyneuritis: Head retraction, incoordination,arched back & hyperextended legs, spastic gait, loss of balance. Infantile Beri-Beri 1. first 6 months 2. breast milk deficient in B-1 3. mother w/o symptoms 4. rapid onset

7 5. cyanosis, tachycardia, labored breathing 6. heart failure and death Wet Beri Beri 1. symptoms similar to congestive heart failure 2. Pitting edema - trunk, limbs, face 3. labored breathing, tachycardia 4. rapid deterioration 5. fatal cirulatory collapse 6. responds rapidly to B-1 supplements Dry Beri-Beri 1. no edema 2. progressive wasting 3. numbing and weakening of extremities 4. chronic infections Riboflavin (Vitamin B2) 1. vitamin B 2, lactoflavin (ovo, hepato, verdo), vitamin G 2. a heterocyclic flavin linked to ribose analogous to the nucleosides in RNA 3. orange-yellow fluorescent compound 4. found in significant quantities in green leafy vegetables, milk and meats 5. heat stable, but easily destroyed by light 6. recommended intake is related to energy intake (kcal) RDA 1 2 mg/day H 2C H H C H H C H It chemically has a three rings structure H H C C H H H 3C N N Chemical Characteristics (isoalloxazine) linked to ribose moiety. Riboflavin is a yellow to orange- yellow powder, soluble in water (1:3000 to 1:20000) due to internal crystalline structure, urea or niacinamide are used to solubilize riboflavin when high concentrated solution needed. Functions of Riboflavin 1. 2 cofactors are involved: H 3C N RIBFLAVIN N H

8 a) riboflavin phosphate (flavin mononucleotide, FMN) b) flavin adenine dinucleotide (FAD) 2. involved in the metabolism of carbohydrates, fats and proteins (flavin dehydrogenases/flavoproteins) 3. hydrogen carriers in the respiratory chain Riboflavin deficiency seldom seen in industrialized societies deficiency when seen: Niacin 1. cheilosis (vertical fissure in the lips) 2. angular stomatitis (craks in the corner of the mouth) 3. glossitis 4. photophobia 5. seborrheic dermatitis 6. normochromic normocytic anemia 7. usually encountered along with pellagra (niacin deficiency) 8. newborns treated for hyperbilirubinemia by phototherapy (riboflavin is unstable to light) 9. Generalized dermititis & growth failure. Marked keratitis of cornea. Structure Nicotinic Acid = Niacin Nicotinamide = Niacinamide Cofactor Forms of Niacin Nicotinamide Adenine Dinucleotide NAD Nicotinamide Adenine Dinucleotide Phosphate NADP Niacin is found in most foods, although meat is the major source. It can also be made by the body from the amino acid tryptophan. RDA: 19 mg for men, 15 mg for women function: It is required for the release of energy from food, for the normal structure of the skin and mucous membranes and for normal functioning of the nervous system. deficiency: a disease called pellagra (symptoms: high sensitivity to sunlight, aggression, dermatitis, red skin lesions, insomnia...) Nicotinic acid is sometimes prescribed by doctors (as a drug) to treat high blood lipid levels, i.e. hyperlipidaemia (excess fat in the blood).

9 hypervitaminosis: rare, headache, nausea, burning and itching skin Chemical Characteristics of Niacin relatively stable to 1. light 2. heat 3. oxidation 4. alkali major losses due to leaching Digestion and Absorption of Dietary Niacin 1. Coenzyme form in food 2. hydrolysis in small intestine to free vitamin 3. absorbed in duodenum 4. nicotinic acid protein bound in corn requires alkali treatment (lime) to release niacin Deficiency of B-3 1. Pellegra 2. Dermatitis scaly dermatitis, sun exposed 3. Dementia confused, disoriented 4. Diarrhea irritation/inflammation of mucous membranes Niacin Toxicity 1-3g/day for treatment of hypercholesterolemia increases histamine release skin flushing increase risk of peptic ulcers liver injury time release forms greater risk of liver injury

10 Pantothenic acid (Vitamin B 5) 1. It is a peptide substance composed of Pantoic acid and b-alanine. 2. It can be present as the Calcium salt or the Alcohol Pantothenol. 3. a yellow viscous oil (free acid) 4. stable to moist heat (not to dry heat) and to oxidizing and reducing agents 5. hydrolyzed in acid or alkaline medium 6. sources (numerous): liver, kidney, eggs, lean beef, milk, molasses, cabbage, cauliflower, broccoli, peanuts, sweet potatoes, kale (derive its name from everywhere) sources: beef liver, lean meats, milk, eggs, legumes, whole grain products, most vegetables A recent study also suggests that gut bacteria in humans can generate pantothenic acid RDA: 4 7 mg function: Pantothenic acid is needed to form coenzyme-a (CoA), and is critical in the metabolism and synthesis of carbohydrates, proteins, and fats. deficiency: rare, fatigue, nausea, loss of appetite, mental depression hypervitaminosis: general lack of toxicity Pyridoxine (Vitamin B6) Vitamin B6 comprising 3 forms pyridoxine, pyridoxal and pyridoxamine. widespread occurrence 1. pyridoxine: mostly in vegetable products 2. pyridoxal and pyridoxamine: mostly in animal products pyridoxine is stable in acid solution, but unstable in neutral or alkaline solutions (destroyed by light sources: is found in a variety of foods: beef, fish and poultry are rich sources. It also occurs in eggs, whole-grains and some vegetables. RDA: 2 mg for men, 1,6 mg for women CH CH 2 NH 2 CH 2 H H CH 2 H H CH 2 H H CH 2 H H 3 C N H 3 C N H 3 C N PYRIXXAL PYRIDXAMINE PYRIDXINE

11 function: It is essential as a coenzym in protein metabolism, necessory for formation of hemoglobin and red blood cells, needed for glycogenolysis and gluconeogenesis. Together with folate and vitamin B12, vitamin B6 is required for maintenance of normal blood homocysteine levels. Raised homocysteine is a risk factor for cardiovascular disease. deficiency: a complication of cardiovascular disease, nerve damage, anemia hypervitaminosis: loss of nerve sensation, deficiency: 1. difficult to produce in humans 2. may be accomplished artificially with a pyridoxine antagonist (deoxypyridoxine) 3. symptoms include: nausea and vomiting, seborrheic dermatitis, depression and confusion, mucous membrane lesions, peripheral neuritis, anemia Biotin (Vitamin B 7 or H) 1. an imidazole sulfur containing compound 2. sometimes referred to as vitamin B7 or vitamin H 3. widely distributed in foods (liver, kidney, milk, molasses) 4. a large portion of the daily need of biotin is met by synthesis by intestinal bacteria 5. deficiency is usually the result of a defect in utilization rather than simple dietary deficiency deficiency: 1. quite uncommon requirements: mcg/day Folate (vitamin B 9) Folic acid is the synthetic form of the vitamin and 2. can be induced by feeding raw egg white (avidin) 3. avidin is a protein which binds tighly with biotin (MW 70,000) 4. symptoms are: anorexia, nausea, muscle pain, fine scaly desquamation of the skin the most stable. It is used in supplements and for food fortification. Various folates are found in both plant and animal foods. sources: liver, yeast extract, orange juice and green leafy vegetables. Various foods, e.g. breakfast cereals and bread may be fortified with folic acid. RDA: 200 µg for men, 180 µg for women

12 function: Folate is essential for normal cell division and in the formation of blood cells. It is also needed for the normal structure of the nervous system and specifically in the development of the neural tube (which develops into the spine and skull) in the developing embryo. Together with vitamins B6 and B12, folate is involved with the maintenance of normal blood homocysteine absorbed by both active and passive transport on the average we absorb ug per day (about 10-25% of dietary intake) storage is in the form of 5-methyl THF (5-20 mg) found in green vegetable, dietary yeasts, liver, kidney bacteria synthesize their own folic acid (dihydropteroate synthetase) Increasing intakes of folate through supplements of folic acid, before conception and during the first twelve weeks of pregnancy, prevents the majority of neural tube defects (e.g. spina bifida) in babies. It is recommended that all women of childbearing age, and especially those planning a pregnancy and who are in the early stages of pregnancy, take a daily supplement of 400μg folic acid as it is difficult to achieve this amount of additional folate by diet alone. Women s diets typically provide about 250 μg folate/day. hypervitaminosis: may prevent of detection of pernicious anemia (caused by B 12 deficiency) Folate Deficiency 1. Megaloblastic Anemia 2. decreased DNA synthesis 3. failure of bone marrow cells to divide 4. normal protein synthesis 5. results in large immature RBC s 6. contrast with microcytic hypochromic anemia Cyanocobalamin (Vitamin B12) sources: Dietary intake is exclusively from animal sources, e.g. milk, meat and eggs (and fortified foods). Although some bacteria can make vitamin B12, it is probably not in a form that can be used by the body. Fortified breakfast cereals can be a useful source of this vitamin. RDA: 2 µg

13 function: B12: 1. normal cell division and normal blood formation, for the normal structure and function of nerves. 2. Together with folate and vitamin B6, it is required for the maintenance of normal blood homocysteine levels; raised blood homocysteine is a risk factor for cardiovascular disease. synthesized by bacteria only red in color, levorotatory and stable to heat commercially available either as cyano or hydroxocobalamin stored in the liver as the coenzyme absorbed only in the presence of the intrinsic factor (a glycoprotein released by parietal cells) transported to tissues via transcobalamin II present in foods such as liver, fish, eggs, milk absent in vegetables and fruits by far the most complex vitamin in structure made up of a planar corrin ring (4 pyrroles) the only vitamin that possesses a metal ion (cobalt) as part of its structure the major cofactor form of B12 is adenosylcobalamin or 5 -deoxyadenosylcobalamin small amounts of methylcobalamin also occur (intermediate in methyl transfer reactions) Causes of B 12 deficiency Pernicious anemia (autoimmune gastritis against parietal cells - loss of intrinsic factor) rarely due dietary deficiency oral contaceptive drugs intestinal parasite gastrectomy chronic gastritis Schilling test Vitamin A (Retinol) The fat soluble vitamins Retinol and beta carotene preformed vitamin A. Beta carotene can be converted to retinol in the body; 6mg of beta carotene is equivalent to 1mg of retinol.

14 sources: 1. Retinol is found in liver, whole milk, cheese and butter. 2. Carotenes are found in milk, carrots, dark green leafy vegetables and orange coloured fruits, e.g. mango and apricots. 3. The law states that margarine must be fortified with vitamin A (and vitamin D). 4. RDA (retinol): 1000 mcg of retinol, or 5000 IU, for adult males and 800 mcg of retinol, or 4,000 IU, for adult females 5. one glass of milk provides 10% of the RDA 6. one medium carrot provides 200% of the RDA 7. a serving of liver provides 900% of RDA Major function in the body 1. vital to good vision 2. prevents night blindness 3. antioxidant 4. necessary for healthy skin, hair growth 5. keeps mucous membranes healthy 6. promotes bone development 7. Vitamin A is stored in the body in relatively large amounts, and thus deficiencies are rare. deficiency: night blindness, intestinal infections, impaired growth hypervitaminosis: nausea, headache, fatigue, liver and spleen damage, skin peeling, risk of birth defect.it is for this reason that women who are pregnant, or who might become pregnant, are advised not to take vitamin A supplements unless they are advised to do so by a health professional. Liver and liver products may contain a large amount of vitamin A, so these should also be avoided. Exits in 3 forms: all trans-retinol long chain fatty acyl ester of retinol (main storage form) retinal (the active form in the retina) retinoic acid is also considered to be physiologically active provitamin A or carotene can be converted to retinol in vivo H3 C CH 3 CH 3 CH 3 CH 2 H CH 3 VITAMIN A (RETINL)

15 Diseases of deficiency: 1. Nigh blindness and xerophthalmia (dry eye) 2. Skin disorders 3. Lack of growth Hypervitaminosis: A serious potential problem (CNS disorders; birth defects) Additional role of retinol retinol also functions in the synthesis of certain glycoproteins and mucopolysaccharides necessary for mucous production and normal growth regulation this is accomplished by phosphorylation of retinol to retinyl phosphate which then functions similarly to dolichol pho Vitamin D (Cholecalciferol) Vitamin D is found in foods in two main forms, mostly as cholecalciferol and in small amounts as ergocalciferol. The physiologically active form is calcitriol, which is the hormone of this vitamin. The ultraviolet rays from sunshine convert a compound found in the skin into cholecalciferol which is released into the blood and is eventually converted by the liver and kidneys into active hormone calcitriol. In this form it works as a hormone in controlling the amount of calcium absorbed by the intestine. It is also essential for the absorption of phosphorus and for normal bone mineralization and structure. sources: fish liver oils, eggs, tuna, salmon, fortified foods like dairy products and margarine, and some breakfast cereals, action of sunlight on the skin = deficiencies are unusual RDA (cholecalciferol): 10 micrograms or 400 IU 1. one glass of milk provides 25% of RDA 2. one tin of sardines provides 100% of RDA There are 2 major precursor forms: 1. 7-dehydrocholesterol 2. ergosterol UV irradiation affords cholecalciferol (vitamin D 3 ) and ergocalciferol (vitamin D 2 ) RDA 20 mg (required in minute amounts) disease of deficiency: rickets Hypervitaminosis Malformation of bones due to improper bone mineralization Toxic dose only 10X higher than the RDA

16 Causes hypercalcemia can lead to cardiac arrest vitamin D is not a vitamin (or a cofactor) it is a steroid hormone Major function in the body 1. acts as a hormone to increase intestinal absorption of calcium 2. promote bone and tooth formation 3. prevents rickets in children and osteomalacia in adults deficiency: rickets in children and osteomalatia in adults, Deficiencies are rare. Some groups of people (e.g. older adults, and children) are at risk of vitamin D deficiency because of low vitamin D intake from food and/or inadequate exposure of skin to sunshine. hypervitaminosis: loss of appetite, nausea, joint pains, loss of muscle tone, damage to soft tissues such as the kidney, heart, and blood vessels due to deposits of calcium. Vitamin E (alpha-tocopherol) Vitamin E is a group of compounds called tocopherols and tocotrienols, of which alpha tocopherol is the most active. sources: vegetable oils, margarine, green leafy vegetables, wheat germ, whole grain products, egg yolks RDA (tocopherol): 10 mg for men, and 8 mg for women one tablespoon of margarine provides 74% of RDA Major function in the body 1. helps breakdown polyunsaturated fats

17 2. antioxidant, protect cells against oxidative damage by free radicals, for example oxidation of the lipids in the cell membranes 3. plays a role in aging, sexual performance, or prevention of cancer and/or heart disease deficiency: disruption of red blood cell membranes, anemia Deficiencies are extremely rare. hypervitaminosis: headache, fatigue, diarrhea, general lack of toxicity with doses up to 400 mg Vitamin E is one of the most popular nutrient supplements. There are many health claims for supplementation slowing of the aging process or an improvement in sexual potency. Vitamin K (phylloquinone) the coagulation vitamin exists in 2 forms: plant origin: phylloquinone or vit K 1 bacterial origin: menaquinones or vit K 2 also certain synthetic quinones have vitamin K activity menadione (vitamin K 3 ) menadiol sodium phosphate (vitamin K 4 ) Vitamin K is found in foods from both plant and animal sources and is also made by bacteria in the gut. sources: beef liver, eggs, spinach, cauliflower, broccoli, tomatoes RDA: 80 µg for men, 65 µg for women Major function in the body essential for clotting of blood (vitamin K is named antihemorrhagic vitamin) normal bone structure deficiency: increased bleeding and hemorrhage Deficiency states are rare, they may occur in some individuals when antibiotic medications kill the intestinal bacteria that produce the vitamin. hypervitaminosis: thrombosis, vomiting CH 3 CH 3 CH 3 3 CH 3 PHYTNADINE (VITAMIN K 1 ; PHYLLQUINNE)