Calcium and vitamin D. Thumbs up. Extra calcium to protect bone health is safe and routinely prescribed for adults who get too little from food. In one study, men who consumed the most calcium (about 2,000 mg. a day) were 25 percent less likely to die over the next decade than their peers who got the least, according to findings published in 2010 in the American Journal of Epidemiology. The Iowa Women's Health Study also found that calcium supplements were associated with reduced risk of death over nearly two decades.
And consensus is building that Americans need more vitamin D to promote calcium uptake. It is produced by sun-exposed skin and is difficult to get from unfortified foods—fatty fish is the only major food source. Studies suggest vitamin D also may help fend off cancer and ward off infections. Still, no large-scale randomized controlled clinical trials prove vitamin D supplements offer benefits beyond bone health. Researchers are hungry for more evidence.
In 2010, the Institute of Medicine released new recommendations for daily calcium and vitamin D intake. Between 600 and 4,000 international units of vitamin D are advised, depending on age and gender, and between 700 and 2,500 milligrams of calcium.
Fish oil. New findings are at odds with past evidence for the worth of the omega-3 fatty acids in fish oil, especially for heart-related conditions. An April analysis published in the Archives of Internal Medicine found that fish oil may not do much to ward off heart attacks and strokes in people who already have heart disease. Those taking fatty acid pills had about the same rates of heart disease, death from heart attacks, congestive heart failure, and stroke as those on placebo pills. But the findings don't necessarily mean that fish oil supplements are useless in heart patients. The study participants were all taking statins, powerful cholesterol-lowering medications, which could have trumped any benefits from fish oil.
The American Heart Association continues to recommend 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, taking 1,000 mg or so is a good idea.
Antioxidants. The glowing promise of antioxidants 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 chronic disease epidemiologist with Brigham and Women's Hospital and coauthor of the Physicians' Health Study-II papers.
Many observational studies suggest that people who gobble antioxidant-laden fruits and veggies or supplements have a reduced 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 vitamin E may actually increase the risk of lung cancer among smokers, as has been found with beta carotene, as noted above. 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.
Researchers are still studying whether supplemental antioxidants might slow the progression of age-related macular degeneration and perhaps prevent noise-related hearing loss. But "no doctor would recommend them for the prevention of cancer, of cardiovascular disease, or of dementia," says Simon.
What about you? Nutritional profiles are not all the same. Recommended intake varies by age, gender, and even race. And genetic differences mean everyone utilizes or responds to vitamins differently, says K. Simon Yeung, a research pharmacist in the Integrative Medicine Service at Memorial Sloan-Kettering Cancer Center. Diet preferences, such as a low-fat or vegetarian regimen, will alter the mix of nutrients taken in. Moreover, lab tests that analyze the nutrients in your system and indicate which ones might need boosting or trimming are, with a few exceptions, not readily available and not often performed. However, keeping tabs on your dining habits for a few days with SuperTracker, a U.S. Department of Agriculture tool, will give you a sense of whether you're on the right course. (It helps you plan, analyze, and track your diet and physical activity.)