Good vitamin descriptions

FYI: This is long Vitamins, Carotenoids, and Phytochemicals June 1999 By Well-Connected What Are Vitamins and Carotenoids and What Are the Adverse Effects of Deficiencies and Overdose? Vitamins do not share a common chemistry, but they share certain characteristics. They are all organic nutrients that are necessary in small amounts for normal metabolism and good health. Most vitamins must be provided by the diet or by supplements; only three vitamins (D, K, and the B vitamin biotin) can be manufactured in the body from nondietary sources. Vitamins are not sources of energy as are carbohydrates, fats, and proteins. Instead, vitamins serve as chemical partners for the enzymes involved in the body's metabolism, cell production, tissue repair, and other vital processes. Vitamins are either fat soluble or water soluble. The fat-soluble vitamins, which include A, D, E, and K, are absorbed by the body using processes that closely parallel the absorption of fat. They are stored in the liver and used up by the body very slowly. The water-soluble vitamins include C and the B complex vitamins. The body uses these vitamins very quickly; excess amounts are eliminated in urine. The Recommended Daily Allowance (RDA) for vitamins, set by the Food and Nutrition Board of the National Academy of Sciences-National Research Council, is gradually being enhanced using a new standard called the Dietary Reference Intake (DRI). The DRI is a general term for four different rating sets that will apply to vitamins, minerals, and proteins taken by men or women in specific age groups. (1) The Estimated Average Requirement (EAR) is the daily intake that meets the requirements of 50% of the population group. (2) If the EAR is unknown a rating called Adequate Intake (AI) is used, which is an estimate of average intake that seems to be healthy and not dangerous. (3) The Recommended Daily Allowance (RDA) is the amount of a supplement sufficient to meet nearly all needs of men or women in certain age groups. (4) The Tolerable Upper Intake Level (UL) is the maximum dose likely to be safe in nearly all individuals. The full list of nutrients is expected to be completed by 2000. Another standard being developed called Daily Reference Values (DRVs) will cover nutrients and other food components, such as phytoestrogens, fiber, and other nutritional factors, which do not yet have any standards. Because vitamins and other dietary supplements are regulated as food and not drugs by the government, however, no standards exist for effectiveness. Brands differ in quality and in the ability of vitamins to be absorbed by the body; it is nearly impossible for the average consumer to compare them wisely. Shopping for the lowest-priced vitamins is the wisest move; there appears to be no significant differences in quality between the vitamins in the lowest and those in the highest price ranges. The FDA is now requiring that vitamins and other dietary supplements include labels similar to those now found on all commercial foods. The label will include nutrient information and list all ingredients, including identifying parts of plants from which ingredients may be taken, but the quality of the supplement will not be evaluated. The essential problem remains there is no control over what goes into a dietary supplement and not enough known about long term effects and risks. Studies on ginseng, for example, found that some supplements did not contain any active ingredients and that others varied widely in the amount they contained. The U.S. Pharmacopoeia, an independent organization that sets standards for drugs, has implemented standards for vitamins; consumers should look for the USP label on products of companies that adhere to these standards. Vitamin A Vitamin A is part of a group of compounds called retinoids and is essential for growth, bone development, night vision, reproduction, and healthy skin. Vitamin A is present in animal products, such as liver, dairy products, eggs, and fish liver oil. It is also converted from carotenoids, found in dark red, green, and yellow vegetables (see Cartenoids below). Vitamin A is best absorbed in the presence of some dietary fat. Average DRI is 875 mcg. Supplements are rarely recommended for people with normal diets because of the risk of toxicity. Deficiencies of Vitamin A. Deficiencies of vitamin A can cause skin disorders and eye damage; in less developed countries severe deficiencies cause blindness in 250,000 children each year. Diets low in vitamin A may also increase the risk of developing cancer. Deficiencies in the U.S. are rare but can result from inadequate diets in preschool children or in women who are pregnant or breast feeding, from intestinal disorders such as cystic fibrosis, steatorrhea, and biliary obstruction, from hyperthyroidism, and from liver diseases such as cirrhosis. Toxicity of Vitamin A. Vitamin A can be very toxic when taken in high-dose supplements for long periods of time and can affect almost every part of the body, including eyes, bones, blood, skin, central nervous system, liver, and genital and urinary tracts. Symptoms include dizziness, nausea, vomiting, headache, skin damage, mental disturbances, and, in women, infrequent periods. Severe toxicity can cause blindness and may even be life threatening. Liver damage can occur in children who take RDA-approved adults levels over prolonged periods of time or in adults who take as little as five times the RDA-approved amount for seven to ten years. In children, chronic overdose can cause fluid on the brain and other symptoms similar to those in adults. Pregnant women who take amounts not much higher than RDA levels increase the risk for birth defects in their children. High consumption of vitamin A may also increase the risk of gastric cancer and the risk of osteoporosis and fractures in women. B Vitamins The B vitamins have a wide and varied range of functions in the human body. Most B vitamins are involved in the process of converting blood sugar into energy. Diets rich in B vitamins are particularly important for pregnant and breast-feeding women and for other people who require more energy, such as athletes and heavy-labor workers. General Deficiencies of Vitamin B. Deficiencies of B vitamins are uncommon in the U.S., but when they occur, they usually involve several B vitamins, since many of them come from the same food groups. Alcohol interferes with these vitamins, and some of the physical and mental problems that alcoholics experience may be attributed to a deficiency of B vitamins. Elderly people are also at risk for deficiencies, because of inadequate diets and potential interference with B-vitamin absorption by medications. General Toxicity of Vitamin B. Because the B vitamins are water-soluble and eliminated in the urine, toxic reactions from oral administration of most of them are extremely rare. (Exceptions are niacin and B6.) (For specific adverse reactions from deficiencies or high dosage levels, see individual discussions of B vitamins, below). It should be noted that substances known as B15 (pangamic acid) and B17 (laetrile) are neither vitamins nor nutrients; both chemicals are highly dangerous and have no proven nutritional or other value. Deficiencies and Toxicity of Vitamin B1 (Thiamin). Thiamin is essential for converting blood sugar into energy and is involved in metabolic activities in nerves, heart, and muscles and in the production of red blood cells. Thiamin is found in almost all foods, but the best source is pork and good sources are dried fortified cereals, oatmeal, corn, nuts, cauliflower, and sunflower seeds. Recommended RDA is 1.2 mg per day for men and 1.1 mg for women. Supplements for people with normal diets and health are unnecessary. Severe vitamin B1 deficiency, known as beriberi, is rare in the U.S., but can occur in alcoholics, in severely malnourished people, or in those receiving long-term dialysis or intravenous feeding. Symptoms may include visual disturbances, paralysis, staggering, loss of sensation in the legs and feet, psychosis, and congestive heart failure. No toxic effects have been reported for thiamin. Deficiencies and Toxicity of Vitamin B2 (Riboflavin). Like thiamin, riboflavin is important in the production of energy. Some dietary sources are liver, dried fortified cereals, and low fat yogurt. Recommended DRI is 1.7 mg. Supplements for people with normal diets and health are unnecessary. Deficiencies affect the skin and mucous membranes and can cause cracks on the lips or corners of the mouth, eczema of the face and genitals, a burning sensation on the tongue, or eye irritation. Previously, no toxic effects had been reported even from large doses of riboflavin However, one new study indicated that high consumption of vitamin B2 may increase the risk of stomach cancer. (In the same study, vitamins B1, B3, and B6 were protective). Deficiencies and Toxicity of Vitamin B3 (Niacin). Niacin, also known as nicotinic acid, helps break down blood sugar for energy and also acts as a vasodilator, widening blood vessels and increasing blood flow. Dietary sources are mackerel, swordfish, chicken, veal, dried fortified cereals, pork, salmon, and beef liver. Current DRI recommendations are 20 mg. This vitamin may be prescribed for improving cholesterol levels, but supplements are unnecessary in people with normal health and diets. A deficiency of niacin causes pellagra; symptoms can include eczema, intestinal and stomach distress, depression, headache, thinning of the hair, and excess saliva production. Anemia may occur, although this is probably due to an accompanying deficiency in folic acid (see Folic Acid, below). Even mildly high doses of niacin can cause hot flushing of the face and shoulders, headache, itchiness, and stomach problems. Some report heart disturbances and temporarily lowered blood pressure. Large doses may produce ulcers, gout, diabetes, and liver damage, which are usually reversed when high doses are discontinued. Deficiencies and Toxicity of Vitamin B5 (Pantothenic Acid.) Pantothenic acid, like many B vitamins, plays a wide role in the body, including metabolism of fats, carbohydrates, and proteins, as well as production of steroid hormones and other important chemicals. Dietary sources are whole grains, beans, milk, eggs, and liver. Recommended adequate intake (AI) is 4 to 7 mg. Supplements are unnecessary in people with normal health and diets. Deficiency is unlikely except in company with other B vitamin deficiencies. Symptoms include abdominal distress, burning sensation in the heels, and sleep problems. Although no toxicity has been reported in humans, high dosages have caused liver damage in rats. Deficiencies and Toxicity of Vitamin B6 (Pyridoxine). Vitamin B6, or pyridoxine, has an effect on over 60 proteins in the body, importantly, those that play a role in the nervous system, in red and white blood cell production, and in heart disease. Food sources of B6 are meats, oily fish, poultry, whole grains, dried fortified cereals, soybeans, avocados, baked potatoes with skins, watermelon, plantains, bananas, peanuts, and brewer's yeast. Current DRI recommendations are 2 mg in all adults, although for heart protection some experts recommend 3 to 6 mg. Deficiencies are very uncommon but can cause skin problems and nervous system disorders, including impaired memory and concentration. They may also increase the risk for kidney stones. In rare cases, infants are born unable to metabolize pyridoxine; in such cases seizures or convulsions can occur, and vitamin B6 must be administered. Deficiency is associated with increased levels of the chemical homocysteine, which is turn has been associated with heart disease, birth defects, and possibly Alzheimer's disease and dementia. (It is not known if reducing homocysteine levels will have any protective effect.) A diet rich in fruits and vegetables may reduce homocysteine levels. Very high doses (2,000 mg per day) can cause nerve damage with symptoms of instability and numbness in the feet and hands, which may be permanent in some cases. In some cases, the damage may be permanent. Pyridoxine also reduces the effects of L-dopa, the drug used for Parkinson's disease. Deficiencies and Toxicity of Vitamin B12 (Cobalamin). Vitamin B12 is essential for the production of blood cells, manufacturing genetic material, and for healthy functioning of the nervous system. The only natural dietary sources of B12 are animal products, meats, dairy products, eggs, and fish (clams and oily fish are very high in B12); like other B vitamins, however, B12 is added to commercial dried cereals. The RDA is 2.4 mcg a day. Deficiencies are rare in young people, although the elderly may have trouble absorbing natural vitamin B12 and require synthetic forms from supplements and fortified foods. Symptoms of mild B12 deficiency include memory loss, instability, disorientation, and decreased reflexes, and possibly and hearing loss. Deficiencies also elevate homocysteine (see vitamin B6, above). When vitamin B12 deficiencies are caused by a genetic defect, in which a protein known as gastric intrinsic factor is lacking, a serious disorder known as pernicious anemia can develop, which must be treated with injections of vitamin B12 or else neurologic damage may occur. Deficiencies and Toxicity of Biotin. Biotin, also a B vitamin, is involved in the production of amino acid proteins and fatty acids. It is obtained not only in diet but is also produced by bacteria in the intestines. Dietary sources are eggs, milk, liver, mushrooms, bananas, tomatoes, whole grains, nuts, and brewer's yeast. There is no DRI for biotin; some experts suggest 30-100 mcg. Deficiencies are almost unheard of. There is no evidence of toxicity with this vitamin. Deficiencies and Toxicity of Folate. Folate is a B vitamin compound that is important for many metabolic processes in the body and is used in the manufacture of neurotransmitters (chemical messengers in the brain), in preventing heart disease, and for synthesizing DNA. Folate is best found in avocado, bananas, orange juice, cold cereal, asparagus, fruits, green, leafy vegetables, dried beans and peas, and yeast. The synthetic form, folic acid, is now added to commercial grain products. Vitamins are usually made from folic acid, which is about twice as potent as folate. Many experts now recommend that adults have 400 mcg of folic acid daily, which is considerably higher than the DRI recommendations of 400 mcg of folate, which does not take into consideration the possible benefits of folate on the heart. Low levels of folate during pregnancy are common without supplements; deficiencies at that time increase the risk of neural tube defects in newborns. Women who are planning to be pregnant should take 400 mcg of folic acid before conception as well as when they are pregnant or breast feeding. Folate deficiency can cause megaloblastic anemia and affect concentration and memory and may cause hearing loss. As with vitamins B6 and B12, deficiencies also elevate homocysteine, and recent studies are suggesting a strong link between low folate levels and the onset of heart disease. Poor diet coupled with alcoholism is the most common cause of folate deficiency. Any condition that disturbs the small intestine can contribute to folate deficiency. High-dose aspirin, smoking, treatment for seizures, and oral contraceptives may increase the risk for folate deficiency. Some studies have reported a link between high doses and central nervous system disorders, zinc deficiency, and seizures in epileptics. This risk appears to be low, but these results indicate that megadoses of folic acid should be avoided. High amounts in the elderly may also mask symptoms of vitamin B12 deficiencies. Deficiencies and Toxicity of Choline. Choline has recently been recognized as an important B vitamin. It is particularly essential for fetal brain development and for learning and memory. Peanuts, eggs, cauliflower, and meats, especially liver, are good sources of choline. Recommended daily doses are 425 mg for nonpregnant women, 450 mg for pregnant women, and 550 mg for nursing women. Excessive doses can cause intestinal problems, and there is also some concern that high doses can be carcinogenic. Vitamin C (Ascorbic Acid) Vitamin C acts as an antioxidant. It is essential for the production of collagen, the substance that forms the body's connective tissues (bones, cartilage, tendons, and ligaments), and it may help to boost the immune system. Best sources are citrus fruits and juices, papayas, hot chili peppers, bell peppers, broccoli, potatoes, kale, red cabbage, cauliflower, cantaloupe, sweet potatoes, and Brussels sprouts. Good sources are tomatoes and potatoes. The National Institutes of Health now recommend 100 to 200 mg a day. (Smokers need the higher amount.) Deficiencies of Vitamin C. Scurvy is the major vitamin C deficiency disease and affects most body tissues, particularly bones, teeth, and blood vessels. Early symptoms include tiredness, weakness, irritability, weight loss, and vague muscle aches. Later symptoms are bleeding gums, wounds that won't heal, rough skin, and wasting away of the muscles. Low dietary intake of vitamin C may also increase lead levels in the blood. Deficiency has been uncommon in the U.S., usually occurring in the elderly, alcoholics, cancer patients, and some food faddists. Surprisingly, a recent study suggested that many healthy middle-class Americans were deficient in vitamin C. High doses of aspirin taken over a long period of time can interfere with vitamin C and may cause a deficiency. Toxicity of Vitamin C. Adverse effects from vitamin C supplements are uncommon, but high doses (more than 1000 mg per day) may cause headaches and intestinal and urinary problems, including kidney stones. Studies have suggested that in doses of only 500 mg or more vitamin C may actually have pro-oxidant effects (as opposed to being a beneficial antioxidant in normal levels) and can damage cells. Because ascorbic acid increases iron absorption, people with certain blood disorders, such as hemochromatosis, thalassemia, or sideroblastic anemia, should particularly avoid high doses. Large doses can also interfere with anticoagulant medications, blood tests used in diabetes, and stool tests for diagnosing colon cancer. A condition called rebound scurvy is caused by abrupt withdrawal from long-term ingestion of large doses of the vitamin. In rare cases, infants of pregnant women who have taken large doses of vitamin C have been born with rebound scurvy. Vitamin D Vitamin D is actually a term for several hormones that are stored mainly in the liver and also in fat and muscle tissue. Vitamin D is essential for maintaining healthy bone structure because of its role in the absorption and metabolism of calcium. It is easily absorbed during digestion and is excreted from the body very slowly. It is manufactured in the body from a chemical reaction to the ultraviolet radiation in sunlight and is found in a few food sources, including vitamin D fortified milk, fatty fish, egg yolk, and liver. The AI (adequate intake) level is 200 IU (5 micrograms) per day for children and most adults, 400 IU (10 micrograms) for people over 50, and 600 IU (15 micrograms) for those over 70 who do not have sufficient exposure to sunlight. Some experts believe that many people now may require supplements to achieve the recommended levels. Deficiencies of Vitamin D. Deficiencies result in rickets in children and osteomalacia in adults; both diseases are characterized by a softening of the bones caused by low amounts of calcium and phosphorous. Vitamin D deficiency also increases the risk for hip fractures in postmenopausal women. It is also associated with a higher risk for prostate cancer and breast cancer risk, especially in ------------------ http://webpotential.com/ericibs/index.htm