Vitamin D

(from Berkeley Wellness alert)

Because of growing evidence about the benefits of vitamin D—for bone health, muscle function, and possibly even prevention of some cancers and other illnesses—many people are rushing out to buy vitamin D pills. Here’s what to look for.

There are two main forms of vitamin D:

Vitamin D3 (cholecalciferol) is typically derived from lanolin from sheep’s wool. Less commonly, D3 comes from fish liver oil, a concern because of mercury, PCBs, and other possible contaminants—though reputable manufacturers can remove harmful compounds in processing. D3 is also the form our skin produces when exposed to sunlight and is the natural form found in food.

Vitamin D2 (ergocalciferol) comes from non-animal sources, such as fungi, that are exposed to ultraviolet light to convert their cholesterol-like substances, called sterols, into vitamin D.

Once consumed, both vitamin D2 and vitamin D3 are converted in the body to the active form. But some research strongly suggests that D3 is preferable to D2. One study, for example, found that D2 was less than one-third as potent as D3 and that it was shorter-acting.

Reading labels: The type of vitamin D is listed on supplement bottles in the ingredients (and sometimes in the “Supplement Facts” panel). Look for D3 or cholecalciferol, preferably not from fish liver oil. The same company may use D3 in some of its products but D2 in others. If you’ve been taking a supplement with D2 (ergocalciferol), you are still getting benefits, but consider switching to a product with D3 when you are done with that bottle. Some strict vegetarians may prefer D2 since it’s not derived from animals, but because it’s less potent, higher doses are needed to get the same effect as D3.



Many vitamin D pills, multivitamins, and bone formulas—especially those from major brands like One-A-Day and Centrum—contain D3, as does most milk and other fortified foods. Quite a few health-food store brands, however, may still contain D2.

Your D needs: A growing number of experts believe that the current recommended daily intake levels for vitamin D (which range from 200 to 600 IU, based on age) are too low, and that a better goal for everyone is 800 to 1,000 IU a day—especially if you are over 60 (the ability to manufacture vitamin D from sunlight and utilize it declines with age), have darker skin (which makes less vitamin D), live at northern latitudes, or are housebound. You can get some vitamin D from foods—such as milk, fatty fish, and foods fortified with vitamin D—but it’s nearly impossible to get 800 to 1,000 IU without also taking a supplement.