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United States Department of Agriculture

Agricultural Research Service

B12 – More Important Than You Think
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By Gerald Combs, Jr.

Mom was right when she encouraged you to eat meat, dairy products and eggs. These foods have always been good sources of vitamin B12, in addition to being rich in other vitamins and minerals.

Today, is it thought that significant? Vitamin B12 deficiency is relatively rare in the United States. But, emerging evidence suggests that less severe deficiencies of the vitamin do occur and may contribute to heart disease – the country’s number one cause of death. In addition, an Agricultural Research Service-funded study found that volunteers with very low plasma vitamin B12 levels were at greater risk of osteoporosis than those with higher levels.

Vitamin B12 is actually a family of compounds called cobalamins that are essential for health. The name comes from the fact that the vitamin contains cobalt, an element related to iron. But where did the 12 in B12 come from? This vitamin—which is vital to the formation of red blood cells and to a healthy nervous system, was the twelfth of these particular water-soluble vitamins to be characterized. In fact, it was the last member of the vitamin B complex to be recognized, which occurred just after World War II.

Vitamin B12 was discovered as a result of studies conducted to look into the causes of anemia, or too few red blood cells, and the ability of certain foods to prevent anemia in humans and animals. The anemia of vitamin B12 deficiency causes fatigue, shortness of breath, and pallor; but these symptoms can be masked by supplements of another vitamin--folic acid.

Vitamin B12 deficiency also leads to other symptoms that cannot be masked and that are not readily corrected. These include nerve disorders such as numbness, tingling, poor balance, loss of concentration, poor memory, insomnia and mood changes, although each of these symptoms can have other causes.

Vitamin B12 is made only by bacteria. Therefore, it is not found in plant foods. It does occur in dairy products and meats from cows, sheep, and bison, which, themselves, absorb the vitamin made by bacteria in their fore stomachs. It also occurs in meats from chickens and pigs, which are fed the vitamin directly. Typical mixed diets that contain these foods provide at least twice the recommended daily allowance for vitamin B12, which is 2.4 micrograms per day for both men and women.

Two groups, however, are at risk of not getting enough vitamin B12. The first includes individuals with low intakes of animal products, including strict vegetarians. The second group includes individuals over 50 years of age. Studies show that between 10 percent and 30 percent of people in this age group are unable to absorb vitamin B12 from their food. This can happen as a result of diminished production of stomach acids and digestive enzymes that free vitamin B12 from food proteins. In addition, reduced production of other small proteins lowers their ability to assist the absorption of the vitamin by the small intestine. Therefore, the USDA Dietary Guidelines for Americans (http://www.health.gov/dietaryguidelines/) recommends that all persons over 50 get their vitamin B12 from dietary supplements and fortified foods. Cyanocobalamin is the synthetic form of vitamin B12 that is used in the United States to fortify foods and to make dietary supplements. You’ll see the name, cyanocobalamin, listed on food or supplement labels.

Animal protein foods, such as fish, liver, beef, pork, milk and cheese are good sources of vitamin B12. For a list of selected food sources sorted by vitamin B12 content, visit this web page (http://www.ars.usda.gov/Services/docs.htm?docid=9673) at ARS' Nutrient Data Laboratory, and scroll down to "Vitamin B12."


Last Modified: 2/7/2006