Vitamin B12 is a water-soluble and complex vitamin that serves as a precursor to the enzymes methionine synthase and L-methylmalonyl-CoA mutase. These enzymes contribute toward energy production, cancer prevention and a lowered risk of cardiovascular disease. According to the Linus Pauling Institute, it is unlikely to have an excessively high amount of vitamin B12 in your body because once your body reaches its needs for the vitamin, the percentage of the vitamin your gastrointestinal tract absorbs decreases significantly. Injected forms of B12 may have a more profound effect on your serum level, however.
Average Levels
The Drexel University College of Medicine reports that the average serum values for vitamin B12 are between 200 picograms and 900 picograms per milliliter of fluid. Blood tests measure biologically active vitamin B12, so the chances of an incorrect result are low. To obtain a normal blood serum level of vitamin B12, the average healthy adult over the age of 14 needs to consume around 2.4 mcg of the vitamin per day. The average adult currently consumes between 3 mcg and 4.5 mcg of vitamin B-12 each day without experiencing high serum levels.
High Serum Causes
If your body does not appear to be excreting excess vitamin B12, it may be a sign of a serious condition. Drexel University reports that people with liver diseases such as cirrhosis or hepatitis could experience elevated levels of vitamin B12. Raised amounts in your blood may also be a sign of myeloproliferative disorders, which cause abnormal blood cell growth in your bone marrow.
Side Effects
There are no known side effects associated with consuming vitamin B12, even at high doses. The Linus Pauling Institute reports that doses as high as 1,000 mcg have been given to patients with pernicious anemia without any recorded side effects. The patients received these high-level doses through both oral supplementation and intramuscular injection. There is not a tolerable upper intake level for vitamin B-12 established by the Institute of Medicine, as of summer 2011.
Benefits
Consuming more than your daily needs for vitamin B12 ensures that you have an adequate amount in your blood at all times, which can be useful as you get older and your ability to absorb the vitamin decreases. Having high levels of vitamin B12 may help your body convert the chemical homocysteine into the amino acid methionine. According to the Harvard School of Public Health, this serves a dual purpose. First, methionine is a building block your body needs to create proteins. Second, lowering homocysteine likely also lowers your chances for heart disease.
References
- Drexel University School of Medicine; Vitamin B-12 Level; Linda J. Vorvick, M.D., et al.; March 2010
- Linus Pauling Institute; Vitamin B12; Jane Higdon, Ph.D.; March 2003
- Harvard School of Public Health: Three of the B Vitamins -- Folate, Vitamin B6, and Vitamin B12
- "Dietary Reference Intakes: The Essential Guide to Nutrient Requirements"; Food and Nutrition Board; 2006
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