Take a Supplement
Given all these uncertainties, it’s no surprise that all the experts interviewed for this article believe in taking vitamin D daily. Lichtenfeld takes a multivitamin, but the others consider that just a starting point. Giovannucci, who lives in Boston, aims for 1,500 IU daily, but thinks that 1,000 to 2,000 IU might be appropriate for “those with very little sun exposure.” In Omaha, Heaney takes a once-weekly 10,000 IU pill, but suggests 1,000 IU as a good daily goal for all adults. “It won’t be enough for some, it will be enough for many, and everybody will get some benefit.”
Whatever you choose, avoid the D2 form of the vitamin, sometimes called “ergocalciferol.” Though widely used in fortification and supplements, it’s much less potent than the vitamin D3 form. Look for the terms “vitamin D3” or “cholecalciferol” on labels. And don’t opt for cod liver oil as your source, says Heaney. Though it’s loaded with vitamin D, it’s also rich in vitamin A, which most Americans don’t lack: “You could run the risk of toxicity.”
A Sunnier Future
Modern life may have made it harder to get the vitamin D we need daily, but luckily the solutions are simple and close at hand. A couple of servings of fatty fish weekly, a few glasses of milk and an occasional egg yolk—plus fortified foods, supplements and perhaps a little sunshine. It doesn’t sound like a complicated prescription, but it can go a long way toward sending old-time diseases like rickets and osteomalacia back into ancient history where they belong. And, just maybe, it can help ward off modern-day scourges like cancer and diabetes in the future.