Vitamins PDF

Vitamins Dr. Doa’a Dwairej  Introduction Vitamins are organic (carbon-containing) compounds that are essential in small amounts for body processes. Vitamins themselves do not provide energy. They enable the body to use the energy provided by carbohydrates, fats, and prot...

Vitamins Dr. Doa’a Dwairej  Introduction Vitamins are organic (carbon-containing) compounds that are essential in small amounts for body processes. Vitamins themselves do not provide energy. They enable the body to use the energy provided by carbohydrates, fats, and proteins. They should not be overused megadoses can be toxic. Vitamins are found in minute amounts in foods. The specific amounts and types of vitamins in foods vary.  Introduction Many of the 13 known vitamins are currently named according to their chemical composition or function in the body  Vitamin deficiencies Persons inclined to vitamin deficiencies because: – They do not eat balanced diets include alcoholics, the poor and incapacitated elderly, patients with serious diseases that affect appetite, mentally retarded persons, and young children who receive inadequate care. – Deficiencies of fat-soluble vitamins occur in patients with chronic malabsorption diseases such as cystic fibrosis, celiac disease, and Crohn’s disease.  Classification of vitamins Vitamins are commonly grouped according to solubility: – A, D, E, and K are fat-soluble – B complex and C are water-soluble. provitamin – Is found in foods. – This is a substance from which the body can synthesize (manufacture) a specific vitamin. – Carotenoids are examples of precursors of vitamin A and are referred to as provitamin A.  Fat soluble vitamins The fat-soluble vitamins A, D, E, and K are chemically similar They are not lost easily in cooking but are lost when mineral oil is ingested After absorption, fat-soluble vitamins are transported through the blood by lipoproteins because they are not soluble in water  Fat soluble vitamins Excess amounts can be stored in the liver. – Therefore, deficiencies of fat-soluble vitamins are slower to appear than are those caused by a lack of water-soluble vitamins – Because of the body’s ability to store them, megadoses of fat-soluble vitamins should be avoided, as they can reach toxic levels.  Vitamin A Vitamin A consists of two basic dietary forms: – Preformed vitamin A, also called retinol, which is the active form of vitamin A – Carotenoids, the inactive form of vitamin A, which are found in plants. Functions – Vision – bone growth – Reproduction – cell division – regulate the immune system – Antioxidant (provitamin A ;carotenoids)  Vitamin A Antioxidants protect cells from free radicals. – Free radicals are atoms or groups of atoms with an odd (unpaired) number of electrons. – Once formed, these highly reactive radicals can start a chain reaction. When they react with important cellular components such as DNA or cell membranes, the most damage occurs. – Antioxidants have the capability of safely interacting with free radicals and stopping the chain reaction before vital cells are damaged.  Vitamin A Sources – Preformed vitamin A (retinol) is found in fat-containing animal foods such as liver, butter, cream, whole milk, whole-milk cheeses, and egg yolk. It is also found in low-fat milk products and in cereals that have been fortified with vitamin A, but these are not the best sources. – Provitamin A carotenoids (beta-carotene) The best sources of beta-carotene are carrots, sweet potatoes, spinach, broccoli, pumpkin, squash (butternut), mango, and cantaloupe  Vitamin A Requirements – A well-balanced diet is the preferred way to obtain the required amounts of vitamin A. – A retinol equivalent is 1 μg retinol or 6 g beta carotene Hypervitaminosis – Signs of hypervitaminosis A may include Birth defects, hair loss, dry skin, headaches, nausea, dryness of mucous membranes, liver damage, and bone and joint pain. – In general, these symptoms tend to disappear when excessive intake is discontinued.  Vitamin A Deficiency. – Signs of a deficiency of vitamin A include: Night blindness; dry, rough skin; and increased susceptibility to infections. – Avitaminosis A can result in blindness or xerophthalmia, a condition characterized by dry, lusterless, mucous membranes of the eye. – Lack of vitamin A is the leading cause of blindness in the world (discounting accidents).  Vitamin D Vitamin D exists in two forms D2 and D3. – Each is formed from a provitamin when exposed to ultraviolet light. – They are equally effective in human nutrition, but D3 is the one that is formed in humans from cholesterol in the skin. – D2 is formed in plants. Vitamin D is considered a prohormone because it is converted to a hormone in the human body.  Vitamin D Functions – Promotion of calcium and phosphorus absorption in the body – Building and maintenance of normal bones and teeth – Prevention of tetany Vitamin D is absorbed in the intestines and is chemically changed in the liver and kidneys. Excess amounts of vitamin D are stored in the liver and in adipose tissue.  Vitamin D Sources – The best source of vitamin D is sunlight, which changes a provitamin to vitamin D3 in humans – The amount of vitamin D that is formed depends on the individual’s pigmentation (coloring matter in the skin) and the amount of sunlight available. – The best food sources of vitamin D are milk, fish liver oils, egg yolk, butter, and fortified margarine.  Vitamin D Because of the rather limited number of food sources of vitamin D and the unpredictability of sunshine, health authorities decided that the vitamin should be added to a common food. Milk was selected Requirements – People who are seldom outdoors, those who use sunscreens, and those who live in areas where there is little sunlight for 3 to 4 months a year should be especially careful that their diets provide their AI levels of vitamin D.  Vitamin D Requirements – Drinking 2 cups of vitamin D–fortified fat-free milk each day will provide sufficient vitamin D to those between birth and 50 years of age.  Vitamin D Hypervitaminosis. – Hypervitaminosis D must be avoided because it can cause deposits of calcium and phosphorus in soft tissues, kidney and heart damage, and bone fragility. Deficiency – Young children suffering vitamin D deficiency may develop rickets – Adults lacking sufficient vitamin D may develop osteomalacia, softening of bones.  Vitamin E Functions – Vitamin E is an antioxidant. It is aided in this process by vitamin C and the mineral selenium. – It is carried in the blood by lipoproteins. – Vitamin E has been found helpful in the prevention of hemolytic anemia among premature infants. – It also may enhance the immune system  Vitamin E Sources – Vegetable oils made from corn, soybean, safflower, and cottonseed and products made from them, such as margarine, are the best sources of vitamin E. – Wheat germ, nuts, and green leafy vegetables also are good sources Requirements – Research indicates that the vitamin E requirement increases if the amount of polyunsaturated fatty acids in the diet increases. diet is thought to contain sufficient vitamin E  Vitamin E Deficiency – A deficiency of vitamin E has been detected in premature low-birthweight infants and in patients who are unable to absorb fat normally. – Malabsorption can cause serious neurological defects in children, but in adults, it takes 5 to 10 years before deficiency symptoms occur.  Vitamin K Vitamin K1, commonly called phylloquinone, is found in dietary sources K2, called menaquinone, is synthesized in the intestine by bacteria and is also found in animal tissue. Vitamin K is absorbed like fats, mainly from the small intestine and slightly from the colon. Its absorption requires a normal flow of bile from the liver, and it is improved when there is fat in the diet.  Vitamin K Functions – Formation of prothrombin, which permits the proper clotting of the blood. Sources – Green leafy vegetables such as broccoli, cabbage, spinach, and kale – Dairy products, eggs, meats, fruits, and cereals – Cow’s milk is a much better source of vitamin K than human milk – The synthesis of vitamin K by bacteria in the small intestine does not provide a sufficient supply by itself. It must be supplemented by dietary sources.  Vitamin K Requirements Adequate intake of vitamin A men 120 g women 90 g Infants up to 6 months 2.0 g – Vitamin K must be ingested daily. – What is absorbed today will be utilized immediately with very little storage in the liver.  Vitamin K Hypervitaminosis – Ingestion of excessive amounts of synthetic vitamin K can be toxic and can cause a form of anemia. Deficiency – Defective blood coagulation. This increases clotting time, making the client more prone to hemorrhage. – Human deficiency may be caused by faulty fat metabolism, antacids, antibiotic therapy, inadequate diet, or anticoagulants.  Water soluble vitamins Water-soluble vitamins include B complex and C. These vitamins dissolve in water and are easily destroyed by air, light, and cooking. They are not stored in the body to the extent that fat-soluble vitamins are stored.  Vitamin B Complex Vitamin B complex is composed of eight B vitamins: – B-1 (thiamine) – B-2 (riboflavin) – B-3 (niacin) – B-5 (pantothenic acid) – B-6 (pyridoxine) – B-7 (biotin) – B-9 (folic acid) – B-12 (cobalamin)  Vitamin B12 Vitamin B12 – Vitamin B12 (cobalamin) is a compound that contains the mineral cobalt. – It is slightly soluble in water and fairly stable to heat, but it is damaged by strong acids or alkalies and by light. – It can be stored in the human body for 3 to 5 years.  Vitamin B12 Functions – Involved in folate metabolism – maintenance of the myelin sheat and healthy red blood cells – A patient who has lost the ability to produce the gastric secretions, pancreatic proteases, intrinsic factor, or the special receptor cells because of disease or surgery will develop pernicious anemia.  Vitamin B12 Sources – The best food sources of B12 are animal foods, especially organ meats, lean meat, seafood, eggs, and dairy products. Requirements – Vitamin B12 is measured in micrograms – The DRI for adults is 2 to 4 g a day, but it increases during pregnancy and lactation. – The amount absorbed will depend on current needs.  Vitamin B12 Deficiency – A vitamin B12 deficiency is rare and is thought to be caused by congenital problems of absorption, which inhibit the body’s ability to absorb or synthesize sufficient amounts of vitamin B12. – It may also be due to years of a strict vegetarian diet that contains no animal foods.  Vitamin B12 Deficiency – When the amount of B12 is insufficient, megaloblastic anemia may result. – If the intrinsic factor is missing, pernicious anemia develops. – Intrinsic factor could be missing because of surgical removal of the stomach, or a large portion of it, or because of disease or surgery affecting the ileum  Vitamin B12 Deficiency – Vitamin B12 deficiency may also result in inadequate myelin synthesis. – This deficiency causes damage to the nervous system. – Signs of vitamin B12 deficiency include anorexia, glossitis, sore mouth and tongue, pallor, neurological upsets such as depression and dizziness, and weight loss.  Folate /folic acid Functions – Folate is needed for DNA synthesis, protein metabolism, and the formation of hemoglobin. – Researchers have concluded that folic acid helps to prevent colon, cervical, esophageal, stomach, and pancreatic cancers. – Folic acid also increases homocystein levels that help prevent strokes, blood vessel disease, macular degeneration, and Alzheimer’s disease.  Folate /folic acid Sources – Cereals fortified with folate – Green leafy vegetables – Legumes – Sunflower seeds – Fruits such as orange juice and strawberries Heat, oxidation, and ultraviolet light all destroy folate, and it is estimated that 50% to 90% of folate may be destroyed during food processing and preparation. Consequently, it is advisable that fruits and vegetables be eaten uncooked or lightly cooked whenever possible.  Folate /folic acid Requirements – The average daily requirement for the adult female is 400 g, and for the adult male it is also 400 g. – There is an increased need for folate during pregnancy and periods of growth because of the increased rate of cell division and the DNA synthesis in the body of the mother and of the fetus. – The recommended amount for a woman 1 month before conception and through the first 6 weeks of pregnancy is 600 g a day.  Folate /folic acid Deficiency – Folate deficiency has been linked to neural tube defects (NTDs) in the fetus, such as spina bifida (spinal cord or spinal fluid bulge through the back) and anencephaly (absence of a brain).  Folate /folic acid Other signs of deficiency are – Inflammation of the mouth and tongue, poor growth, depression and mental confusion. – Problems with nerve functions, and megaloblastic anemia. Megaloblastic anemia is a condition wherein red blood cells are large and immature and cannot carry oxygen properly.  Folate /folic acid Hypervitaminosis – The FDA limits the amount of folate in over-the- counter (OTC) supplements to 100 g for infants, 300 g for children, and 400 g for adults because consuming excessive amounts of folate can mask a vitamin B12 deficiency and inactivate phenytoin, an anticonvulsant drug used by epileptics.  Vitamin C Vitamin C – is also known as ascorbic acid. – It has antioxidant properties and protects foods from oxidation, and it is required for all cell metabolism. – It is readily destroyed by heat, air, and alkalies, and it is easily lost in cooking water.  Vitamin C Functions – Prevent scurvy – Formation of collagen making it necessary for wound healing (the requirement for vitamin C is increased during trauma, fever, and periods of growth) – Vitamin C aids in the absorption of nonheme iron (from plant and animal sources and less easily absorbed than heme iron). – Formation or functioning of norepinephrine some amino acids, folate, leukocytes (white blood cells), the immune system, and allergic reactions.  Vitamin C – It is believed to reduce the severity of colds because it is a natural antihistamine, and it can reduce cancer risk in some cases by reducing nitrites in foods. – Vitamin C is absorbed in the small intestine. Sources – The best sources of vitamin C are citrus fruits, melon, strawberries, tomatoes, potatoes, red and green peppers, cabbage, and broccoli.  Vitamin C Requirements – Vitamin C is measured in milligrams. – Under normal circumstances, an average female adult in the United States requires 75 mg a day and an average male 90 mg. In times of stress, the need is increased. Deficiency – Deficiencies of vitamin C are indicated by bleeding gums, loose teeth, tendency to bruise easily, poor wound healing, and, ultimately, scurvy.