Truth About Vitamin D: Can You Get Too Much Vitamin D?

Can I get too much vitamin D?

Too much of any good thing is a bad thing. Too much vitamin D can cause an abnormally high blood calcium level, which could result in nausea, constipation, confusion, abnormal heart rhythm, and even kidney stones.

It's nearly impossible to get too much vitamin D from sunlight or from foods (unless you take way too much cod liver oil). Nearly all vitamin D overdoses come from supplements.

The Institute of Medicine's Food and Nutrition Board's old 1997 recommendations suggested that 2,000 IU per day of vitamin D is safe for adults and that 1,000 IU per day is safe for infants up to 12 months of age. Many observers expected a drastic increase in the IOM's 2010 update.

That didn't exactly happen. The IOM committee did increase its "upper level intake" -- that is, the boundary at which it feared vitamin D would become unsafe. That dose is 4,000 IU/day for adults, 3,000 IU/day for kids ages 4-8, 2,500 IU/day for kids ages 1-3, 1,500 IU/day for infants ages 6-12 months, and 1,000 IU/day for infants ages 0-6 months.

But some recent studies suggest that healthy adults can tolerate more than 10,000 IU of vitamin D per day. John Jacob Cannell, MD, executive director of The Vitamin D Council, notes that the skin makes 10,000 IU of vitamin D after 30 minutes of full-body sun exposure. He suggests that 10,000 IU of vitamin D is not toxic.

According to the National Institutes of Health, 25-OHD levels that are consistently over 200 ng/mL are "potentially toxic."

The IOM committee found no conclusive evidence that increased vitamin D levels confer increased health benefits, "challenging the concept that '

more is better.'"

Next: What kind of vitamin D is best?

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