Vitamin B12 is a water-soluble vitamin that exists in several forms and is active in human metabolism. The vitamin is essential in the formation of red blood cells, neurological functioning and in the synthesis of DNA. Normally, vitamin B12 is bound to protein in foods and released by the activity of acid in the stomach. When synthetic B-12 is added to fortified foods and other supplements, it doesn't require this separation step.
Vitamin B12
Doctors can evaluate your vitamin B12 status using a blood test to look at your levels, according to the Office of Dietary Supplements. Some evidence suggests that the blood levels of vitamin B12 do not accurately reflect how much B-12 is available inside the cells. When vitamin B12 deficiency occurs, pernicious anemia or megaloblastic anemia is the result, according to MayoClinic.com. However, the human body can store several years worth of vitamin B12 for future use, so a deficiency is rare. Individuals who are most at risk are the elderly who may have an inability to absorb vitamin B12 from the intestinal tract, as well as strict vegetarians or vegans who do not get enough of it in their diet.
Doses
A full day's supply of vitamin B12 can be obtained from food by eating one chicken breast plus one hard-boiled egg and 1 cup of plain low-fat yogurt. If, after consulting with your primary care physician, you feel that additional supplementation will be helpful, the recommended dietary allowance for adults and adolescents over the age of 14 is 2.4 mcg per day, according to MayoClinic.com. This dose is 2.6 mcg for adults and pregnant females and 2.8 mcg per day for adolescents, adults and lactating females. Those over the age of 50 must meet the recommended daily allowance by eating fortified foods or by taking a supplement, because between 10 and 30 percent of older individuals do not absorb food bound vitamin B12 efficiently.
Effectiveness
Vitamin B12 supplementation is available in injectable form as a prescription from your physician. According to Linus Pauling Institute, it is also available as a nasal gel and in over-the-counter preparations included in multivitamins, vitamin B complex combinations and as a separate vitamin B12 supplement. According to the Office of Dietary Supplements, existing evidence does not suggest that there is any difference in bioavailability of vitamin B12 based on different forms of administration. Preparations that are sublingual or lozenges are often marketed as having better bioavailability, but no evidence exists to suggest a difference.
Precautions
Individuals who are allergic to cobalamin, cobalt or any other ingredients in the product should of avoid using vitamin B12 supplements, according to MayoClinic.com. Side effects from vitamin B12 supplementation can include itching, rash and temporary raised rash. It has also been associated with a significant outbreak of rosacea that includes nodules, papules and pustules. These symptoms can persist for up to four months after the supplement has been stopped and may require treatment with systemic corticosteroids. Some patients have reported diarrhea. Vitamin B12 supplementation is contraindicated in Leber's disease, which is a hereditary optic nerve disease causing blindness.
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