Q. I’ve read a lot about the health benefits of Vitamin D. But isn’t there also a limit of how much Vitamin D I should supplement? Is there a danger or limit that avoids a possible toxic amount?
A. The Institute of Medicine recently doubled the safe upper limit (UL) for vitamin D from 2000 IU to 4000 IU. That’s still quite a bit lower than the 10,000+ IU a day that some vitamin D researchers recommend. The IOM tends to be rather conservative and research suggests that 10,000 IU a day is unlikely to cause problems. But I think the IOM may be trying to provide a counter-balance to what some see as “irrational exuberance” being displayed by some vitamin D aficionados.
The science on Vitamin D, while compelling, is still quite immature. While low vitamin D status has been linked to a number of health problems, we still don’t have strong evidence showing that high dose vitamin D supplements make or keep people healthier. In fact, And I just saw some research suggesting that a combination of dietary vitamin D (from food and supplements) and moderate sun exposure (which triggers vitamin D production in the skin) offers the most benefit.
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