Vitamin B-12, a water-soluble vitamin, is the largest and most complex of all 13 essential vitamins. It functions to keep your nerve and blood cells healthy. Deficiencies in vitamin B-12 pose health risks, including anemia and nervous system dysfunction. Additionally, vitamin B-12 participates in the synthesis of methionine, an amino acid formed from homocysteine. Elevated levels of homocysteine in the blood increase your risk for heart disease, according to the American Heart Association, but not all experts agree.
Vitamin B-12
Vitamin B-12 serves as a cofactor for the enzyme methionine synthase. This enzyme is involved in amino acid metabolism, converting homocysteine to methionine. The reaction is required for the proper formation of DNA, your genetic code. When methionine synthase does not function properly, homocysteine levels rise in your blood. Too much homocysteine increases your risk for conditions such as heart disease and stroke. This may be due to damage caused by homocysteine to your arteries, notes the AHA, which can promote blood clots.
Homocysteine
Your homocysteine level is influenced by factors that include genetics and diet. Specifically, B-12 helps reduce homocysteine levels, as do other B vitamins, including folate and B-6. This is likely due to the increased activity of methionine synthase, the enzyme responsible for breaking down homocysteine. The American Heart Association recommends that those at high risk for heart disease pay careful attention to meeting recommended intakes for these important vitamins.
B-12 Sources
Vitamin B-12 is present in a variety of foods. Natural sources of the vitamin include animal foods such as eggs, fish, milk and other dairy products. Beef liver and clams are the highest in vitamin B-12 of all foods. Vegetarian sources include fortified cereals and some brands of nutritional yeast. The vitamin is also available in most multivitamins. Supplements that contain only B-12, or B-12 in addition to other B vitamins, also exist. The daily requirement for adults is 2.4 mcg per day.
Considerations
Although the American Heart Association advises consuming adequate B-12 and other B vitamins to lower homocysteine levels as a way of reducing heart disease risk, not all expert sources agree. According to the National Institutes of Health, supplementation with B-12 does not reduce your risk of cardiovascular disease. The Linus Pauling Institute notes that though B-12 does lower homocysteine levels, further research is needed to determine whether supplementation actually reduces disease risk. It may be that whole foods, not vitamins, are the answer.
References
- Office of Dietary Supplements: National Institutes of Health: Dietary Supplement Fact Sheet: Vitamin B12
- American Heart Association: What is Homocysteine?
- American Heart Association: Homocysteine, Folic Acid and Cardiovascular Disease
- Linus Pauling Institute: Micronutrient Information Center: Vitamin B12
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