Vitamins and Supplements: Do They Work?
The picture is mixed, but thumbs up for vitamin D and fish oil
Clarified on 12/10/08: An earlier version of this article stated that Harvard Men's Health Watch newsletter editor Harvey Simon says his concerns about multivitamins have recently eased. They have eased somewhat for breast cancer but not prostate cancer.
The Institute of Medicine has announced it will review the daily recommended dietary allowance of vitamin D, now from 200 to 600 international units depending on age, gender, and race. Experts put the high end anywhere from 800 IU to 2,000 IU a day. The IOM review is due in early 2010. Until then, while the benefits are unproven, adding 1,000 IU of vitamin D won't likely hurt and could help, especially for people who don't get much sun.
Fish oil. The evidence for the worth of the omega-3 fatty acids in fish oil, especially for heart-related conditions, continues to pile up. In August, a study in the Lancet online found a slightly lower rate of deaths and hospitalizations in heart-failure patients who took a daily 1,000-milligram fish oil supplement. The American Heart Association recommends fish oil supplements for those at high risk of a heart attack. Simon, no fan of nutrients in pill form, says that, for those with heart risks who don't eat fatty fish like tuna and salmon twice a week, adding 1,000 mg or so is a good idea.
Antioxidants. The glowing promise of antioxidants, by contrast, remains elusive. These substances, among them selenium and vitamins A, C, and E, are believed to help sop up molecules called free radicals. These react with other molecules in the body and promote oxidative damage—another name for cellular wear and tear. "There's a lot of data supporting the idea that oxidation, over time, has a role in chronic illnesses," says J. Michael Gaziano, a cardiologist with Brigham and Women's Hospital and VA Boston Healthcare System and coauthor of the recent Physicians' Health Study-II papers.
Many observational studies of people who gobble antioxidant-laden fruits and veggies or supplements suggest they lower the risk of some forms of heart disease and cancer. Most clinical trials, however, do not support this. Some research, in fact, has shown that supplemental beta carotene, another antioxidant, may actually increase the risk of lung cancer among smokers. Vitamin E may do the same. And cancer patients shouldn't add more vitamin C than the amount in a multi; research suggests that too much of the vitamin helps cancer cells withstand treatment. Supplement supporters argue that the observational studies should be taken seriously. But one logical explanation for their results is that people who eat fruits and veggies or take antioxidant supplements may eat better diets overall, have access to better medical care, and get exercise. Or, says Alice Lichtenstein, professor of nutrition science and policy at Tufts University's Friedman School of Nutrition, such people could appear to be healthier because they presumably are eating smaller amounts of meat and processed foods—and therefore are likely to be leaner.
advertisement
