Vitamin B12
Last Updated on Sunday, 28 February 2010 21:09
Vitamin B12 is a water-soluble vitamin that is required for proper red blood cell formation, neurological function, and DNA synthesis. Vitamin B12 functions as a cofactor for methionine synthase and L-methylmalonyl-CoA mutase. Methionine synthase catalyzes the conversion of homocysteine to methionine. Methionine is required for the formation of S-adenosylmethionine, a universal methyl donor for almost 100 different substrates, including DNA, RNA, hormones, proteins, and lipids. L-methylmalonyl-CoA mutase converts L-methylmalonyl-CoA to succinyl-CoA in the degradation of propionate, an essential biochemical reaction in fat and protein metabolism.
Recommended Intake
The Food & Nutrition Board at the Institute of Medicine of the National Academies established recommended dietary allowances for vitamin B12 for children and adults. They are listed below in micrograms (mcg) per day.
| Age | Male | Female | Pregnancy | Lactation |
|---|---|---|---|---|
| Birth to 6 months* | 0.4 mcg | 0.4 mcg | ||
| 7-12 months* | 0.5 mcg | 0.5 mcg | ||
| 1-3 years | 0.9 mcg | 0.9 mcg | ||
| 4-8 years | 1.2 mcg | 1.2 mcg | ||
| 9-13 years | 1.8 mcg | 1.8 mcg | ||
| 14+ years | 2.4 mcg | 2.4 mcg | 2.6 mcg | 2.8 mcg |
Sources of Vitamin B12
| Food | Micrograms (mcg) per serving | Percent Daily Value* |
|---|---|---|
| Liver, beef, braised, 1 slice | 48.0 | 800 |
| Clams, cooked, breaded and fried, 3 ounces | 34.2 | 570 |
| Breakfast cereals, fortified with 100% of the DV for vitamin B12, 1 serving | 6.0 | 100 |
| Trout, rainbow, wild, cooked, 3 ounces | 5.4 | 90 |
| Salmon, sockeye, cooked, 3 ounces | 4.9 | 80 |
| Trout, rainbow, farmed, cooked, 3 ounces | 4.2 | 50 |
| Beef, top sirloin, broiled, 3 ounces | 2.4 | 40 |
| Cheeseburger, double patty and bun, 1 sandwich | 1.9 | 30 |
| Breakfast cereals, fortified with 25% of the DV for vitamin B12, 1 serving | 1.5 | 25 |
| Yogurt, plain, 1 cup | 1.4 | 25 |
| Haddock, cooked, 3 ounces | 1.2 | 20 |
| Tuna, white, 3 ounces | 1.0 | 15 |
| Milk, 1 cup | 0.9 | 15 |
| Cheese, Swiss, 1 ounce | 0.9 | 15 |
| Beef taco, 1 taco | 0.8 | 13 |
| Ham, cured, roasted, 3 ounces | 0.6 | 10 |
| Egg, large, 1 whole | 0.6 | 10 |
| Chicken, roasted, ½ breast | 0.3 | 6 |
*Daily Values were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents among products within the context of a total daily diet. The Daily Value for vitamin B12 is 6 micrograms. Foods providing 20 percent of more of the Daily Value are considered to be high sources of a nutrient, but foods providing lower percentages of the Daily Value also contribute to a healthful diet.
