Too Much Vitamin D?

2 min

First, here’s some background for those who haven’t followed the latest news on vitamin D and calcium. On November 30, 2010, the Institute of Medicine (IOM), an arm of the National Academy of Sciences, recommended increasing the amount of dietary vitamin D most Americans and Canadians should get daily to 600 international units (IUs), triple the 200 IUs recommended in 1997.

The IOM said it based its recommendation on levels of vitamin D needed for bone strength and said that there isn’t enough evidence to demonstrate that low vitamin D causes chronic diseases, as some new research suggests. In fact, low levels of D have been linked through population studies with a higher incidence of autoimmune diseases, a number of types of cancer, psoriasis, and diabetes. The IOM recommended that everyone from infancy through age 70 get 600 IUs of vitamin D daily and that those age 71 and over get 800 IUs daily.

As for calcium, the IOM recommended 700 mg per day for children ages one through three; 1,000 mg daily for kids ages 4 through 8; no more than 1,300 mg daily for those age 9 through 18. IOM said that 1,000 mg daily is enough for adults age 19 through 50 and that beginning at age 51 for women and at age 71 for men the recommended amount is 1,200 mg daily.

I disagree with these conclusions and will continue to recommend that everyone get 2,000 IU of dietary vitamin D daily.

My calcium recommendations also remain the same: women who don’t get adequate calcium from their diets should supplement with 500 to 700 mg of calcium citrate in two divided doses taken with meals, for a total daily intake of 1,000-1,200 mg from all sources. Men should aim for 500 mg from all sources. I don’t recommend calcium supplements for men. (Higher amounts have been linked to increased risks of prostate cancer.) Men should also watch their dairy intake.

I was interested in the comments of my friend and colleague, vitamin D researcher Michael Holick, M.D., Ph.D., in news reports of the IOM recommendations. Dr. Holick told National Public Radio that he sees no downside to increasing vitamin D intake. "When I’ve been recommending for the past decade that people take more than the (officially recommended) 200 units, there was a lot of skepticism. Now they’re recommending three times what we recommended in 1997. "I suspect a decade from now that they’ll be recommending another three- or four-fold higher increase," Holick predicts.

I agree. What’s more, I don’t think there is any possibility of harm in taking the vitamin D dosage I recommend. And I believe evidence will continue to come in supporting the preventive benefits of the dosage I recommend, and possibly even higher.

Andrew Weil, M.D.