Q. In your prior newsletters you have cautioned about not taking too much vitamin D, more than 3000 units a day. How can one overdose on vitamin D? People get thousands of units just being in the sun for an hour! I take 10,000 daily since my level was 15 (The normal range is 30 to 70 nanograms per milliliter).

A. I guess we will find out ten or twenty years from now whether people who are taking massive amounts will be healthier or worse off. Getting vitamin D through a pill through intestinal absorption may have some effects that may be different than getting it from the sun through the skin. There are a lot of unknowns and some early evidence indicates that calcification has been noted in the brain of those with very high levels and there seems to be an increased risk for kidney stones when combined with calcium. It's a gamble at this time and if people wish to take this gamble (that is, by taking more than 5000 units a day), it is up to them. I can't predict yet who is going to be right ten or twenty years from now. For decades doctors thought taking calcium 1000 to 1500 mg daily for osteoporosis was safe, too, until we learned that high amounts increase the risk for heart disease and stroke due to excess calcification of blood vessels.