Which Pills Work?; February 2011; Scientific American Magazine; by Melinda Wenner Moyer; 1 Page(s)

Physicians have recommended vitamin D supplements to their patients for a decade, with good reason: dozens of studies have shown a correlation between high intake of vitamin D—far higher than most people would get in a typical diet and from exposure to the sun—and lower rates of chronic diseases, such as cancer and type 1 diabetes. So when the Institute of Medicine, which advises the government on health policy, concluded in November that vitamin D supplements were unnecessary for most Americans and potentially harmful, patients were understandably confused.

The issue exposes a rift among experts over what constitutes valid proof when it comes to nutrition and could affect medical advice on many other supplements. On the one hand are scientists who insist that the only acceptable standard is the randomized clinical trial, which often compares the effects of a medical intervention, such as high intake of vitamin D, with those of a placebo. The scientists who reviewed the vitamin D findings fall heavily into this camp: trials “typically provide the highest level of scientific evidence relevant for dietary reference intake development,” they wrote. Their report set intake levels based only on clinical trial data.