by Craig Weatherby

We goofed!  An alert reader notified us that last week’s article titled “Vitamin D May Diminish Breast Cancer Risk Drastically” contained a math error.

The mistake (underlined) occurred in the section titled “Study #1”, whose 10^th paragraph said this: “Sadly, the average vitamin D intake in the US is only 320 IU per day, or about one-tenth of the 1,000 IU per day associated with a 50 percent reduction in breast cancer risk in the San Diego team's study.”

What we meant to say was this: “Sadly, the average vitamin D intake in the US is only 320 IU per day, or about one-third of the 1,000 IU per day associated with a 50 percent reduction in breast cancer risk in the San Diego team's study.”

The error arose because the maximum reduction in risk was seen in women who reported a much higher intake level averaging 2,800 IU per day. We were thinking of that intake level when we calculated the fraction that 320 IU would represent (Actually, 320 IU would be a bit more than one-tenth of 2,800 IU).

While the experts say that this very high dose level is generally safe for adults, the women in the study got much of the 2,800 IU per day from seafood (see our chart... sockeye salmon may be the world's richest source of vitamin D). Accordingly, you should discuss with your doctor the appropriateness of taking that much vitamin D in supplemental form.