The B Vitamin You Want Just Enough Of

Like running with scissors, skimping on folate -- an important B vitamin found in beans and greens and in fortified breads, breakfast cereals, and noodles -- is a health accident waiting to happen. Low levels can literally rewrite your DNA, raising cancer risk by muting your tumor-suppressing genes and weakening chromosomes.

But more isn't better. New research shows that big doses of this B vitamin won't bulletproof your cells against cancer. In fact, there's emerging evidence that most of us should AVOID high doses of this Jekyll-and-Hyde nutrient.

The facts: High-dose folic acid (the synthetic folate in supplements) did nothing to lower breast cancer risk in a new 7-year Harvard School of Public Health study. Nor did 8 years of extra folic acid reduce colon cancer risk. In fact, it even may have raised the odds for advanced and multiple tumors, reports the University of North Carolina at Chapel Hill. And despite early promise, this B vitamin hasn't been found to reduce the risk of heart disease, either.

Should you throw away your folic acid pills and toss the fortified grain products in your pantry? Not yet. Truth is, you need enough folate. Period. Get too little and your body can't produce enough thiamine -- one of the basic building blocks of DNA -- yet it increases uracil, a molecule found to raise cancer risk. Get too much, and folic acid seems to fuel the growth of tiny, preexisting cancers and precancers.

How do you get just the folate you need, without going overboard? Here are the new rules:

1. Pregnant, or planning to be? Take 400–600 micrograms (mcg) of folic acid daily. Taken before conception and during the first weeks of pregnancy, folic acid offers 60% to 100% protection against neural-tube defects, which affect a growing baby's brain and spinal cord. Some experts also recommend getting 500 mcg per day if breastfeeding. If you've already had a baby with a neural-tube defect, your doctor may recommend higher doses, but take it only with your physician's guidance.

2. Everybody else: Stick with a multivitamin containing 400 mcg. Few of us get enough folate from our diets -- among the millions who've taken the RealAge Test, about 50% have come up short on this B vitamin. We YOU Docs take a multi containing 400 mcg of folic acid as nutritional insurance, and we think you should, too. Another reason: There's evidence that a genetic quirk (called C677T MTHFR) suppresses folate levels in up to 25% of us, but as yet, there's no widely available test or agreed-upon folate level to guide us . . . though we expect both to be announced in the next 5 to 7 years.

• Getting 400 mcg of folic acid a day may be especially important for women who drink alcohol, even in moderation. Even one drink a day can reduce your body's folate levels. There's some evidence that getting enough folic acid from supplements and/or folate from food can offset the increased risk of breast cancer from having one or more alcoholic drinks per day.

3. Don't fret about overdoing with B-fortified bread or breakfast cereals. Or pasta or flour, either. Enriched grain products have contained extra folic acid since 1998, when the U.S. government decided this move could help reduce neural-tube defects. It worked, cutting these serious birth defects by about 50% or more. If you take a multivitamin, you won't “overdose” if you also eat enriched or naturally folate-filled foods.

4. Even better: Skip enriched, get real. Foods richest in folate include black-eyed peas, Great Northern beans, baked beans, spinach, asparagus, and broccoli. All are near-perfect nutritional packages, brimming with fiber, antioxidants, and a wealth of vitamins and minerals that keep you ultrahealthy.