NEW YORK (Reuters) -- A major review of the scientific literature on the safety of folic acid gives thumbs up to the vitamin supplement, declaring it safe.
"After my review, I'm more in favor of folic acid than I was prior to it," says Dr. Norman R.C. Campbell, associate professor of medicine, pharmacology, and therapeutics at the University of Calgary, Alberta, Canada.
His report, which appears in the August 12/26 issue of the Archives of Internal Medicine, did turn up information suggesting that folic acid might increase damage to nervous tissue, cause zinc deficiency, and increase the risk of cancer and malaria. But the author points out that most of the studies are of "limited scientific value" and that none of these adverse affects have been documented with any certainty.
However, he does caution that folic acid supplements might hide a person's deficiency of vitamin B12, or cobalamin, as measured by blood tests.
According to the researcher, "pure vegetarians and elderly patients would want to ensure that they have adequate vitamin B12."
Cobalamin is a cobalt-containing complex molecule that forms part of vitamin B12. Foods rich in the vitamin -- such as liver, kidney, chicken, beef, pork, fish, eggs, and dairy products -- are usually excluded from the diets of strict vegetarians.
Recent studies have indicated that people getting at least 400 milligrams of folic acid per day could have a reduced risk of heart disease. Several researchers have recommended that the federal government consider mandating that amount of the vitamin in processed grains, including bread, and that it be coupled with vitamin B12 to cover any possible harm from an undiagnosed cobalamin deficiency.
"The major problem with adding a little cobalamin to food is that a lot people who develop a deficiency have little ability to absorb it from the stomach," Campbell notes.
As to possibly overdosing on folic acid, Campbell says he was unable to find any amount that could be considered toxic.
"In general, it's very safe. It's very difficult to determine if there is indeed a dangerous dose. Essentially there are no proven toxicities to folic acid," he says.
However, in his report he concludes that any adverse effects of the vitamin are probably dependent on dose -- the amount consumed. "So if folic acid is increased, use the lowest dose that would supply the benefit," he says.
