How to get the benefits without any of the potential harms

When research recently showed that the drug Niaspan, which is derived from niacin (vitamin B-3), outperformed the powerful new cholesterol-lowering drug ezetimibe (Zetia), it was another win for an important B vitamin.

Even though Zetia’s manufacturer, Merck, said that the study was flawed, niacin supplements have a long history of providing health benefits—most notably boosting HDL “good” cholesterol.

What’s new: Other research indicates that some B-vitamin supplements may actually increase the risk for prostate cancer.

Many people think B vitamins are safe at high doses because they’re water soluble—that is, they don’t accumulate in fatty tissue. But research suggests that taking high doses of B vitamins without a specific deficiency and/or without a doctor’s supervision can be dangerous.

How some key B vitamins affect common medical conditions…*

• Age-related macular degeneration (AMD). Scientists recently analyzed research that involved 5,400 women (age 40 and older) who took either a placebo or a combination of B vitamins—folic acid (the supplemental form of the dietary nutrient folate), vitamin B-6 and vitamin B-12. The incidence of AMD (a leading cause of blindness in adults over age 65) was significantly reduced in the vitamin group after an average follow-up of seven years.

My advice: If you are concerned about developing AMD or have risk factors, such as family history, ask your doctor about taking a daily regimen of folic acid, vitamin B-6 and vitamin B-12.

• Cancer. Many studies have found a link between a low-folate diet and an increased risk for certain cancers, particularly colon, breast, cervical and pancreatic. For this reason, people with cancer risk factors, such as a family history of a particular cancer, often have been advised to take 1,000 micrograms (mcg) or more of folic acid daily—far more than the recommended Daily Value of 400 mcg.

Important finding: A study involving about 643 men over a 10-year period found that those taking folic acid supplements at 1,000 mcg daily were more likely to develop precancerous colon polyps than those taking a placebo (in contrast, dietary folate reduced risk for prostate cancer). There’s also some evidence that high-dose folic acid supplements may increase the risk for prostate cancer. Newer studies dispute the suggestion that folic acid may increase cancer risk.

Bottom line: Adequate folate in the diet is beneficial, but research on high-dose folic acid supplements is mixed.

My advice: To help prevent birth defects, women who plan to get pregnant should be sure to get the daily recommendation of 400 mcg of folic acid and pregnant women should get 600 mcg daily. This supplement also makes sense for people who have been found (via blood tests) to have low levels of folate. This is common in people who drink significant amounts of alcohol, have irritable bowel syndrome or don’t eat a lot of folate-rich foods, such as leafy greens, oranges, beans or whole grains. If you improve your dietary folate intake and/or start taking supplements, ask your doctor to recheck your blood levels and discuss your individual risk-benefit profile. Don’t exceed the Daily Value for folic acid without consulting your doctor.

Read food labels: Fortified foods, such as many breakfast cereals, as well as protein bars, vitamin-fortified waters and other products, contain significant levels of folic acid that should be counted in your total daily intake.

• Cognitive decline. Vitamin B-12 is found only in animal foods, including meat, fish, milk and eggs. Older adults deficient in B vitamins—particularly vitamin B-12—tend to have the greatest declines in memory and other cognitive functions.

My advice: Since virtually everyone absorbs less B-12 with advancing age (due to an age-related decline in the production of stomach acid, a substance that’s required for freeing B-12 from food proteins), it’s wise for adults age 65 and older to take a daily supplement that includes B-12. Talk to your doctor about dosage—some people with chronic fatigue may need B-12 injections. Vegans (people who avoid all animal foods) of any age can take whole-food supplements that contain B-12, such as spirulina and chlorella.

• Hearing loss. In a study of 51,529 male health professionals, men over age 60 with high folate intakes—from food or folic acid supplements—were 20% less likely than men with low levels of the vitamin to develop hearing loss.

My advice: If you are concerned about hearing loss, talk to your doctor about increasing your intake of folate.

• Heart health. People who are concerned about heart health have been advised to supplement their natural folate intake with folic acid. That’s because folic acid lowers levels of homocysteine, an amino acid that damages artery linings and increases the risk for heart disease.

Recent finding: When doctors in Norway gave nearly 3,100 adults a placebo or varying doses of folic acid, participants given folic acid had reductions in homocysteine. However, their rates of death and cardiovascular events (such as heart attacks) were virtually the same as those given a placebo.

My advice: Reduce your homocysteine with folate-rich foods. People who don’t eat a lot of these foods can supplement with a daily multi-nutrient that includes 400 mcg of folic acid. Higher doses are unlikely to benefit the heart.

• Stress. Even people who eat a healthful diet may be low in one or more B vitamins. Psychological stress and the metabolic stress caused by illness or exposure to air pollution or other environmental toxins, as well as alcohol consumption, deplete B vitamins.

My advice: Most people could benefit by taking a B-complex supplement containing all eight B vitamins.

Important: Some people report that they feel worse when they start taking a B-complex supplement.

Read the label: Many products contain yeast, gluten or other substances that can trigger allergic-type reactions in some people. The vitamins sold in health-food stores are usually less likely to contain these allergenic foods than the brands found in supermarkets and large chain drugstores. My favorite brands include Nature’s Way, Country Life and Now Foods.

*Before taking any of these vitamins at doses that exceed the government’s recommended Daily Value, consult your physician.