Subsisting on an all-supplement diet is obviously far from anyone’s ideal. But for a lot of us, every day we take what we consider to be key supplements — vitamin D, essential fatty acids, probiotics, etc — to contribute to our long-term health. But two studies examined by Tara Parker-Pope at The New York Times — “More Evidence Against Vitamin Use” — raise questions about whether vitamins can sometimes cause more harm than good.
One study of men linked both vitamin E and selenium to an increased risk of prostate cancer. And according to a study of women in Iowa, the use of multivitamins, vitamin B6, folic acid, iron, magnesium, zinc, and copper were all associated with increased risk of death. Writes Pope: “The findings translate to a 2.4 percent increase in absolute risk for multivitamin users, a four percent increase associated with vitamin B6, a 5.9 percent increase for folic acid, and increases of three to four percent in risk for those taking supplements of iron, folic acid, magnesium, and zinc.” And some studies conducted by the National Cancer Institute have suggested a connection between beta carotene and lung cancer, and folic acid and precancerous polyps.
It is useful to note that, in some instances, supplement use in these studies tended to increase once people became sick — so the causal relationship isn’t exactly clear. Plus, the studies generally address unusually high doses. But it’s also worth noting that supplements are not miracle cures. We need vitamins and minerals of all stripes — best consumed through food — but you can’t smoke, excessively drink, neglect your diet, and then pop a few pills to undo the damage. Plus, many people take vitamins somewhat arbitrarily and without actually consulting a healthcare professional to determine what their body might actually need. While many health professionals continue to recommend reasonable doses of a few select supplements (vitamin D, EFAs, probiotics), it may well be a case where more is definitely not better.