Saturday, February 12, 2011

Health benefits of vitamin B 12

Vitamin B12 is an essential water soluble vitamin that is commonly found in a variety of foods such as fish, shellfish, meats, and dairy products. Vitamin B12 is frequently used in combination with other B vitamins in a vitamin B complex formulation. It helps maintain healthy nerve cells and red blood cells, and is also needed to make DNA, the genetic material in all cells. Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from protein during digestion. Once released, B12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream.
The human body stores several years' worth of vitamin B12, so nutritional deficiency of this vitamin is extremely rare. Elderly are the most at risk. However, deficiency can result from being unable to use vitamin B12. Inability to absorb vitamin B12 from the intestinal tract can be caused by a disease known as pernicious anemia. Additionally, strict vegetarians or vegans who are not taking in proper amounts of B12 are also prone to a deficiency state.
A day's supply of vitamin B12 can be obtained by eating 1 chicken breast (0.6mcg) plus 1 hard-boiled egg (0.55mcg) plus 1 cup plain low-fat yogurt (1.37mcg) or 1 cup milk (0.92mcg) plus 1 cup raisin bran (1.64mcg).
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Uses based on scientific evidence
Vitamin B12 deficiency
Studies have shown that a deficiency of vitamin B12 can lead to abnormal neurologic and psychiatric symptoms. These symptoms may include: ataxia (shaky movements and unsteady gait), muscle weakness, spasticity, incontinence, hypotension, vision problems, dementia, psychoses, and mood disturbances. Researchers report that these symptoms may occur when vitamin B12 levels are just slightly lower than normal and are considerably above the levels normally associated with anemia. People at risk for vitamin B12 deficiency include strict vegetarians, elderly people, and people with increased vitamin B12 requirements associated with pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, liver or kidney disease.Administering vitamin B12 orally, intramuscularly, or intranasally is effective for preventing and treating dietary vitamin B12 deficiency. An oral dose of 100-250 micrograms/day is usually adequate although patients with absorption difficulties may need 1000 micrograms/day of vitamin B12. Oral preparations should not be used in patients with diarrhea, vomiting, severe neurologic involvement, or in patients likely to be noncompliant to therapy.
Megaloblastic anemia - due to vitamin B12 deficiency
Vitamin B12 deficiency is a cause of megaloblastic anemia. In this type of anemia, red blood cells are larger than normal, and the ratio of nucleus size to cell cytoplasm is increased. There are other potential causes of megaloblastic anemia, including folate deficiency or various inborn metabolic disorders. If the cause is B12 deficiency, then treatment with B12 is the standard approach. Patients with anemia should be evaluated by a physician in order to diagnose and address the underlying cause.
Pernicious anemia
Pernicious anemia (blood abnormality) is a form of anemia that occurs when there is an absence of intrinsic factor, a substance normally present in the stomach. Vitamin B12 binds with intrinsic factor before it is absorbed and used by the body. An absence of intrinsic factor prevents normal absorption of B12 and may result in pernicious anemia. Pernicious anemia treatment is usually lifelong supplemental vitamin B12 given either intramuscularly, intranasally, or by mouth.
Alzheimer's disease
Some patients diagnosed with Alzheimer's disease have been found to have abnormally low vitamin B12 levels in their blood. However, vitamin B12 deficiency itself often causes disorientation and confusion and thus mimics some of the prominent symptoms of Alzheimer's disease. Well designed clinical trials are needed before a recommendation can be made.
Some evidence suggests that folic acid 1mg plus vitamin B12 400mcg and pyridoxine 10mg daily can decrease the rate of restenosis in patients treated with balloon angioplasty. But this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting. An intravenous loading dose of folic acid, vitamin B6 and vitamin B12 followed by oral administration of folic acid 1.2mg plus vitamin B6 48mg and vitamin B12 60mcg taken daily after coronary stenting also does not seem to reduce restenosis and might actually increase restenosis. Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents.
Breast cancer
Researchers at Johns Hopkins University report that women with breast cancer tend to have lower vitamin B12 levels in their blood serum than do women without breast cancer. In a subsequent review of these findings, it was hypothesized that vitamin B12 deficiency may lead to breast cancer because it could result in less folate being available to ensure proper DNA replication and repair. Higher dietary folate intake is associated with a reduced risk of breast cancer. The risk may be further reduced in women who also consume high amounts of dietary vitamin B12 in combination with dietary pyridoxine (vitamin B6) and methionine. However, there is no evidence that dietary vitamin B12 alone reduces the risk of breast cancer.
Cardiovascular disease/hyperhomocysteinemia
Hyperhomocysteinemia (high homocysteine levels in the blood) is a risk factor for coronary, cerebral, and peripheral atherosclerosis, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, and ischemic stroke. Elevated homocysteine levels may be a marker instead of a cause of vascular disease. However, it is not clear if lowering homocysteine levels results in reduced cardiovascular morbidity and mortality. Folic acid, pyridoxine (vitamin B6), and vitamin B12 supplementation can reduce total homocysteine levels, however, this reduction doesn't seem to help with secondary prevention of death or cardiovascular events such as stroke or myocardial infarction in people with prior stroke. More evidence is needed to fully explain the association of total homocysteine levels with vascular risk and the potential use of vitamin supplementation.
There is some evidence that intramuscular injections of 5mg of vitamin B12 given twice per week might improve the general well being and happiness of patients complaining of tiredness or fatigue. However, fatigue has many potential causes. Well designed clinical trials are needed before a recommendation can be made.
High cholesterol
Some evidence suggests that 7.5mcg of vitamin B12 in combination with 5 grams of fish oil might be superior to fish oil alone when used daily to reduce total serum cholesterol and triglycerides. Well designed clinical trials of vitamin B12 supplementation alone are needed before a conclusion can be drawn.
Imerslund-Grasbeck disease
Administering vitamin B12 intramuscularly seems to be effective for treating familial selective vitamin B12 malabsorption (Imerslund-Grasbeck disease). Further research is needed to confirm these results.
Shaky-leg syndrome
Preliminary clinical reports show that cyanocobalamin may help relieve tremor associated with shaky-leg syndrome. Further research is needed to confirm these results.
Sickle cell disease
One study suggests that a practical daily combination may be 1mg folic acid, 6mcg vitamin B12, and 6mg vitamin B6. This combination may be a simple and relatively inexpensive way to reduce these patients' inherently high risk of endothelial damage. Further research is needed to confirm these results.
Circadian rhythm sleep disorders
Taking vitamin B12 orally, in methylcobalamin form, does not seem to be effective for treating delayed sleep phase syndrome. Supplemental methylcobalamin 0.5 to 1mg three times daily, with or without bright light therapy, does not seem to help people with primary circadian rhythm sleep disorders.
Lung cancer
Preliminary evidence suggests that there is no relationship between vitamin B12 status and lung cancer.
In people with a history of stroke, neither high dose vitamin B12 combinations containing 25mg of pyridoxine, 0.4mg of vitamin B12, and 2.5mg of folic acid nor low dose combinations containing 200mcg of pyridoxine, 6mcg of vitamin B12, and 20mcg of folic acid seem to affect risk of recurring stroke.
Leber's disease
Vitamin B12 is contraindicated in early Leber's disease, which is hereditary optic nerve atrophy. Vitamin B12 can cause severe and swift optic atrophy.
Uses based on tradition or theory
The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Aging, AIDS, allergies, amyotrophic lateral sclerosis, asthma, boosting energy, chronic fatigue syndrome, depression, depressive disorder (major), diabetes, diabetic peripheral neuropathy, hemorrhage, immunosuppression, improving concentration, improving mood, inflammatory bowel disease, kidney disease, liver disease, male infertility, memory loss, multiple sclerosis, malignancy, osteoporosis, periodontal disease, protection from tobacco smoke, psychiatric disorders, seborrheic dermatitis, tendonitis, thyrotoxicosis, tinnitus, tremor, vitiligo

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