Vitamin B12
What is it? Overview Usage Side Effects and Warnings

What is Vitamin B12?

Vitamin B 12 , an essential nutrient, is also known as cobalamin. The cobal in the name refers to the metal cobalt contained in B 12 . Vitamin B 12 is required for the normal activity of nerve cells and works with folate and vitamin B 6 to lower blood levels of homocysteine , a chemical in the blood that might contribute to heart disease. B 12 also plays a role in the body's manufacture of S-adenosylmethionine (SAMe) .

Anemia is usually (but not always) the first sign of B 12 deficiency. Earlier in this century, doctors coined the name "pernicious anemia" for a stubborn form of anemia that didn't improve even when the patient was given iron supplements. Today we know that pernicious anemia comes about when the stomach fails to excrete a special substance called intrinsic factor....

It appears that individuals who take medications that dramatically lower stomach acid, such as H2 blockers or proton pump inhibitors , would benefit by taking B 12 supplements. 1 2 3 4 5 Other individuals likely to be deficient in B 12 , such as the elderly, or those taking the medications listed in Requirements/Sources, might well benefit from a daily B 12 supplement to prevent B 12 deficiency.

For pernicious anemia, B 12 injections are traditionally used but research has shown that oral B 12 works just as well, provided you take enough of it (between 300 and 1,000 mcg daily). 6 7 8 Weak evidence suggests that B 12 supplements may improve sperm activity and sperm count; on this basis, they could be useful for male infertility . 9 Some cases of recurrent...

Safety Issues

Vitamin B 12 appears to be extremely safe. However, in some cases very high doses of the vitamin can cause or worsen acne symptoms. 10

Interactions You Should Know About

If you are taking:

Colchicine , AZT , medications that reduce stomach acid (such as the H2 blocker ranitidine [Zantac] or the proton pump inhibitor omeprazole [Prilosec], oral hypoglycemics (such as metformin or phenformin), slow-release potassium supplements, or if you are exposed to nitrous oxide anesthesia: You may need extra B 12 . Another option is to take extra calcium , which may, in turn, improve B 12 absorption.