People who take a multivitamin and eat foods with added vitamins, like some cereals and nutrition bars, may be increasing their risk of cancer from excessive folic acid. This could be the result of a  Food and Drug Administration mandate to add folic acid, a B vitamin, to our food supply.

Folic acid is the synthetic form of the B vitamin, folate, which is needed to produce healthy cells. A deficiency results in an abnormally low amount of red blood cells. Folate also helps break down the amino acid, homocysteine, which benefits the heart and arteries.

More folate is needed by pregnant women, especially in the first trimester, to prevent serious birth defects, including spina bifida, but many women run short because they are not aware of being pregnant until months later.

In an effort to reduce birth defects, the FDA implemented the folic acid fortification program in January 1998. Manufacturers are required to add 140 micrograms of folic acid per 100 grams of grain to cereals, breads, pasta, rice and other products labeled "enriched.� National health surveys from 1988-96 found most people did not consume enough folate, but after the fortification program, they consumed recommended amounts.

This change in our food system has decreased birth defects by 45 percent and reduced heart attacks and strokes. But some are questioning if a rise in certain cancers, particularly colon cancer, might be another effect.

More research is under way to answer this question, but what should a consumer do now?

Continue to eat your leafy greens, citrus fruits, and legumes that contain natural folate. There is no risk of overdoing this type because the body adjusts how much will be absorbed. Synthetic folic acid, the type used in multivitamins and added to foods, is rapidly absorbed and must be converted to folate. It lingers in the body and some scientists believe large amounts might help cancer cells grow.  

The daily value on food labels is set at 400 mcg. If you eat a cereal with 100 percent of the daily value (400 mcg), and take a multivitamin containing 400 mcg, and eat a fortified nutrition bar, like say a Luna Bar with another 400 mcg � you would exceed the upper limit. It is best to get the complete benefit of a multivitamin, and avoid highly fortified foods in general. Here are some tips.

- Choose a multivitamin with 400 mcg folic acid or less per serving.

- Avoid cereals (Total, Kashi Heart to Heart, Special K and others that provide 100 percent of the  daily value for folic acid) if you take a multivitamin.

- Choose nutrition bars � like Nature Valley, Kashi, Trader Joe�s and others � that do not add vitamins to their product (aim for 0 to 25 percent of the daily value of folic acid).

- Check labels of protein shakes, Slim Fast, meal replacement bars/cookies to avoid going over the 1,000 mcg daily limit.

Joan Endyke is a registered dietitian with a master�s degree in nutrition and food science, and also a certified personal trainer. She is the nutrition director at Fitness Unlimited. Readers may send questions about nutrition to Endyke at Fitness Unlimited, 364 Granite Ave., Milton,  MA 02186 or  jendyke@fitnessunlimited.com. The information in this column is not intended to diagnose individual conditions. Readers should see their doctors about specific problems.