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Vitamin D: Update: Vit D2 vs D3 & How Much Sun? PDF Print E-mail
Written by Jeff Novick, M.S., R.D.   
Sunday, 13 July 2008 13:21

Vitamin D3 is often regarded as the best source of Vitamin D "if" someone was to need to take a supplement. However, recent evidence shows that Vitamin D2 may be as effective as Vitamin D3.

The following Q & A's come from a very recent article from Micheal Holick, who is considered the worlds leading expert on Vitamin D. I am copying his responses to the Vitamin D2 vs D3 quesion along with the response to how much sun expsoure is required for the body to manufcature adequate amounts of Vitamin D. For those who would like to read the full article, I have include a link to it also.

For those not familair with him, Michael F. Holick, PhD, MD, is professor of medicine, physiology, and biophysics; director of the General Clinical Research Center; and director of the Bone Health Care Clinic and the Heliotherapy, Light, and Skin Research Center at Boston University Medical Center.

Q: Has recent research shown that both vitamin D 2 and D3 are equally effective at increasing the levels of 25-hydroxyvitamin D? This is in opposition with earlier studies, is it not?

Dr Holick: That’s correct. There was a study done in Canada in which researchers gave a group of adults 4000 IU of vitamin D 2 or 4000 IU of vitamin D 3 in ethanol for a period of 2 weeks and showed wide variability, and there appeared to be a 50% reduction in the 25-hydroxyvitamin D levels in the adults who were taking vitamin D 2. This implied that vitamin D2 was less effective than vitamin D 3. The second study that set this kindling on fi re was the observation by Dr Heaney’s group. They gave a single 50 000-IU dose of vitamin D 2 or a single 50 000-IU dose of vitamin D3 to healthy adults in the summertime. When they followed their 25-hydroxyvitamin D levels, they found that the levels more rapidly declined in the group that got that single dose of vitamin D 2. But more importantly and alarmingly was that the 25-hydroxyvitamin D 3 in those same subjects more rapidly declined than the subjects who received a placebo, implying that the vitamin D 2 induced the destruction of vitamin D 3. Therefore, not only was vitamin D 2 less active, but it caused the destruction of vitamin D3.

I decided to conduct a study in which we gave 1000 IU of Vitamin D 2 or 1000 IU of vitamin D3 to healthy adults at the end of the winter—Dr Heaney’s study was done in the summer, and sun exposure may have infl uenced the outcome of the study. We found that vitamin D 2 raised the blood levels of 25-hydroxyvita-min D identically to the group that took vitamin D 3. More importantly, to leave no stone unturned, we also made a capsule that contained 500 IU of vitamin D 2 and 500 IU of vitamin D 3 and showed that the 25-hydroxyvitamin D levels increased exactly the same degree for the 25-hydroxyvitamin D 2 and 25-hydroxyvitamin D 3 and that there was no alteration in the 25-hydroxyvitamin D 3 levels in the group that got vitamin D 2. That, to me, proves that vitamin D 2 is as effective as vitamin D 3 in raising and maintaining 25-hydroxyvitamin D levels. That is consistent with the early literature that showed that 100 IU of vitamin D 2 was effective in preventing rickets in children.

Q: How much vitamin D does a person get from exposure to the sun?

Dr Holick: We did a study that showed that if you expose a person in a bathing suit to what we call 1 minimal erythemal dose, which is a light pinkness to the skin 24 hours after sun exposure, it’s equivalent to taking between 15 000 and 20 000 IU of vitamin D 3. For a white adult, that would be equivalent to being exposed to sunlight in June at noon for about 10-15 minutes on a Cape Cod beach. Your body has a huge capacity to make vitamin D. What’s interesting is that the sunlight destroys any excess vitamin D that your body makes, so you could never become vitamin D intoxicated from sun exposure

ALTERNATIVE THERAPIES, May/jun 2008, VOL. 14, NO. 3, 64-75.
Conversations: Michael Holick, PhD, MD.
Interview by Frank Lampe and Suzanne Snyder. Photography by David Keough.


(NOTE: For those of you who are following a vegan lifestyle, Vit D2 would be the preferred option as Vitamin D3 is animal derived.)

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