Why is it that so many people need to take a vitamin D supplement in order to have optimal levels? We're supposed to be able to make vitamin D after we go into the sunlight. But I have reported to you in the past that for most people, sunlight is just not enough. And here's another question. Why do some of us need to take such high vitamin D doses in order to have optimal levels? I need to take 15,000 units a day. And many of my patients need even more than that. But why?

Most doctors and researchers have assumed that the problem comes from aging, the use of sun blocks, sunglasses, shunning the sun, and staying indoors. But that can't be the reason. There have been too many reports of tanned young men who work construction all day long outdoors in Hawaii wearing only swim trunks without sun blocks or sunglasses that can't get close to optimal levels. Now, finally, we are getting some answers to these questions. It's genetics.

Researchers reported just last month that certain genetic variations in vitamin D binding protein can account for the problem. According to the authors, "Common genetic variants in the CYP2R1 and GC genes modify vitamin D concentrations in the same manner after artificial ultraviolet exposure induced vitamin D and consumption of vitamin D3-fortified bread and milk." They are saying that the same genetic differences that account for why so many people can't get adequate vitamin D levels from sun exposure also accounts for why they often need to take such high doses.

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The scientists learned this when they exposed 92 healthy men and women to the same doses of ultraviolet vitamin D-stimulating light. They measured their vitamin D levels before and after. Then they analyzed 25 different gene variations involved in vitamin D synthesis, transport, activation, or degradation. Sure enough, they were able to predict who would respond best to the ultraviolet light simply by seeing the pattern in these genetic variations.

To study the effect of vitamin D supplements, they did the same kind of before and after study on 201 healthy Danish families who were given vitamin D3-fortified bread and milk or placebo for six months during the winter. The results were the same. The same genes determined how much vitamin D you can make from sunlight as well as how much you can get from your diet or supplements. But here's the point.

You can't take these gene tests anyway. They are not commercially available. Even if they were, who cares? Just get as much sunlight as you can without getting sunburned. And take as much vitamin D supplements as you need to get your blood levels up to the optimum of 60-75 ng/ml. For some, it won't take much (start at 5,000 IU daily) and for others it will take a lot. I have written extensively on the safety and health benefits of taking vitamin D this way. And if you aren't familiar with how important optimal vitamin D levels are, you can find all of those reports in the archives on my website.

Yours for better health,

Frank Shallenberger, MD

REF:

Nissen J, Vogel U, Ravn-Haren G, et al. Common variants in CYP2R1 and GC genes are both determinants of serum 25-hydroxyvitamin D concentrations after UVB irradiation and after consumption of vitamin D3-fortified bread and milk during winter in Denmark. Am J Clin Nutr. 2015 Jan;101(1):218-27.