UnCategorized Vitamin C or L-Ascorbic Acid is not manufactured by the body. It must be obtained through diet or supplementation. It is a water soluble vitamin found in the juices of fruits and vegetables and readily leaches into the cooking water of boiled foods. It is very sensitive to oxidation and is destroyed whenever foods are cut or torn which exposes the cells to air. Alkalies such as baking soda or antacids destroy ascorbic acid. Vitamin C is a very important antioxidant and is required for at least 300 metabolic functions in the human body. This includes tissue growth and repair, adrenal gland function, and healthy gums. It also aids the production of anti-stress hormones and interferon which is an important immune-system protein. It must also be present for the metabolism of folic acid, tyrosine and phenylalanine. Taking vitamin C can reduce the symptoms of asthma. Ascorbic acid protects against the harmful effects of pollution, helps prevent cancer, protects against infection, and enhances immune system function. It increases the absorption of iron and can combine with toxic substances, like certain heavy metals, and render them harmless and allow them to be eliminated from the body. Very large doses of vitamin C may even render the venom of the black widow spider harmless. This vitamin may also reduce levels of LDL (the bad cholesterol) while it increases levels of HDL (the good cholesterol) and lower high blood pressure to help prevent atherosclerosis. It is essential for the formation of collagen. Collagen is a protein that forms the basis for connective tissue, the most abundant tissue in the body. Collagen binds muscle cells together, gives support and maintains shape in intervertebral discs and eustachian tubes, and provides movement in joints. Vitamin C protects against abnormal blood clotting and bruising. It may reduce the risk of cataracts and promotes healing of wounds and burns. Vitamins C works in concert with both vitamin E and beta-carotene. Taking these vitamins together allow them to repotentiate each other and may counter potential adverse effects of taking them separately. Vitamin E works to scavenge dangerous free radicals in cell membranes, while vitamin C scavenges free radicals in biologic fluids. These vitamins reinforce and extend the antioxidant activity of the other. Ascorbic acid has a role in amino acid metabolism and hormonal synthesis. It contributes to the formation of tyrosine (the precursor for the neurotransmitters epinephrine and norepinephrine). During periods of stress these hormones are mobilized, and the small stores of ascorbic acid in the adrenal glands are depleted. Therefore, vitamin C may help the body deal more effectively with stress. Tryptophan is converted to 5-hydroxytryptophan in the presence of vitamin C and is decarboxlated to form the neurotransmitter serotonin. CANCER: Cancer risk is reduced by the antioxidant characteristics of vitamin C. Researchers at Trinity College in Dublin, Ireland found that free-radical activity damages DNA, which might initiate carcinogenic changes in colonic mucosa. Vitamin C suppresses this damage and limits adenomatous polyp growth in patients with colorectal cancer. This vitamin acts as a cytotoxic agent in cancerous cells to reverse chemically-transformed cells back to a normal phenotype. Vitamin C, together with beta-carotene, reverses cervical dysplasia, leukoplakia, and gastric metaplasia. CARDIOVASCULAR DISEASE: A study at the University of California, Los Angeles, compared heart disease mortality rates in individuals with the highest and lowest vitamin C intakes and found that regular supplementation with vitamin C reduced the mortality rate from cardiovascular disease by 45%. DIABETES: Ascorbic acid may help regulate insulin action in diabetics according to a study conducted at the National Institutes of Health. The study indicates that ascorbic acid participates in insulin regulation by inhibiting glucose-induced insulin release in pancreatic islets. IMMUNE SYSTEM: A marginal ascorbic acid deficiency results in compromised immune system function according to a study from USDA Agriculture Research Service in San Francisco and UCLA School of Public Health in Los Angeles. This was despite the absence of clinical deficiency symptoms. Moreover, researchers at Arizona State University in Tempe report that high intakes of vitamin C stimulate the immune system response by degrading and detoxifying histamine and might indirectly enhance neutrophil chemotaxis. COMMON COLD: Finnish researches reviewed current research on ascorbic acid and the common cold. They found that most studies report the vitamin to have only a small effect on cold prevention. However, the studies consistently show this vitamin helps reduce a cold’s duration and severity. Vitamin C supplements given in therapeutic doses (1 to 8 grams/day) at the onset of a cold reduce the duration of cold episodes by as much as 48%. VISION: Levels of vitamin C in the eye are 20 to 70 times greater than that found in plasma and other tissues. This vitamin plays a key role in proper ocular function by protecting the eye against light-induced loss of retinal pigment, epithelial cells, and photoreceptor cells. It also eliminates O2 from the lens and protects against UV radiation. There is some evidence that links higher intakes of this vitamin with a reduced risk of age-related macular degeneration. Low intakes of this vitamin may increase the risk for developing cataracts. Low levels to none are found in cataractous lenses, while human lenses with senile cataracts have increased levels of free radicals. It is unknown whether these associations are the cause or result of cataracts. In vitro studies have shown that ascorbic acid may benefit glaucoma in the human eye. CAUTIONS: Do not take aspirin and large doses of standard ascorbic acid together. Doing so may lead to stomach irritations, possibly contributing to ulcer formation. If you take aspirin regularly, use a buffered form of vitamin C, and take it separately from the aspirin. If pregnant, take no more than 5,000 mg of ascorbic acid per day. A developing infant may become dependent on this supplement and develop scurvy when deprived of the accustomed megadoses after birth. Avoid using chewable forms of this supplement, as these can damage tooth enamel. About the Author: 相关的主题文章: