Vitamin B12 is one of eight important B vitamins. All of the B vitamins are water-soluble, meaning they are not stored by the body, except for B12, which is stored in small amounts. This vitamin is unique and plays several important roles throughout your body. B12 is readily available in many foods, but in some cases you may require a dietary supplement. You only need a few mcg of B12 each day, so taking a 1,000 mcg supplement may be excessive. Check with your physician as a precaution before you begin taking B12 supplements.
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Your body requires 2.4 mcg of B12 each day. If you are pregnant, this amount increases to 2.6 mcg, reports the Office of Dietary Supplements. Breastfeeding drains your B12 stores, so you need as much as 2.8 mcg of B12 each day while lactating. Consuming 1,000 mcg of B12 from diet and supplements far exceeds what your body needs.
Toxicity of B12
Vitamin B12 is relatively safe, even at high doses of up to 1,000 mcg. While consuming 1,000 mcg of B12 from supplements or from your diet may not pose a health threat, you can only absorb about 10 mcg per day, explains the Linus Pauling Institute. Toxicity risk of B12 is low since your body absorbs such a small amount, excreting any excess.
Functions of B12
Vitamin B12 is necessary for red blood cell formation, proper neurological function, as well as the synthesis of DNA, the genetic material found in each cell. B12 comes in several forms, but it is usually paired with the mineral cobalt. In this form, the B12 compound is referred to as a cobalamin, common in dietary supplements. Cobalamins are easily converted into methylcobalamin and 5-deoxyadenosylcobalamin, the two types of active B12 compounds in your body. In food, B12 is bound to protein and must be released by stomach acids in order to function. Synthetic B12, in supplements and fortified foods, is already in a free state and does not need this extra step, explains the Office of Dietary Supplements. Adding 1,000 mcg of B12 to your diet doesn't improve these functions or processes since you can only absorb a small amount.
Foods Rich in B12
If you are generally healthy, adding a 1,000 mcg supplement to your diet isn't necessary since this vitamin is in several food sources. Animal meat and seafood are excellent sources of B12. A 3-oz. serving of fried clams provides 34.2 mcg; salmon has 4.9 mcg; and trout provides 4.2 mcg per 3-oz. serving. Enjoying a small 6-oz. sirloin steak has nearly 5 mcg of vitamin B12. You can also get B12 from a variety of dairy foods. An 8-oz. glass of milk provides about 1 mcg of B12; 1 cup of yogurt contains 1.4 mcg; and a 1-oz. slice of Swiss cheese has 0.9 mcg. Additionally, having a fried egg for breakfast provides approximately 0.6 mcg of vitamin B12.