Could Your Sunscreen Be Causing Vitamin Deficiency?

Continuing on Skin Cancer Awareness Month, the topic of Vitamin D deficiency has become a hot topic around my house as both myself and my husband are, in fact, Vitamin D deficient. In the words of one of my colleagues:"Yeah, so what else is new? We all are" -- the "we" in this sentence being white-people-who-live-in-the-Pacific-Northwest.

So what's the connection with the sun, you might ask? Vitamin D is a pretty neat vitamin mostly because humans photosynthesize it via sunlight. Isn't that just the coolest thing? Briefly, it goes something like this: sunlight (UVB, specifically) hits the cell membranes of skin cells containing a particular lipid (7-dehydrocholesterol). With the help of the sunlight, this lipid is transformed into pre-Vitamin D (cholecalciferol or Vitamin D3). Pre-Vitamin D then makes it way into the blood stream, making pits stops in the liver and kidneys to be hydroxylated, and becoming active Vitamin D which then goes on to modulate genes and other fancy stuff in the rest of the body. Without sunlight, this whole process cannot happen.

After learning about my low Vitamin D level, I couldn't help but wonder if it had something to do with sunscreen. Presumably, if sunscreen is blocking both UVA and UVB rays that cause cancer and photo-aging, then wouldn't it make sense that it is also blocking the body's ability to synthesize Vitamin D? Thus began my tour of the scientific literature to find an answer. Stupidly, I didn't check the Skin Cancer Foundation's helpful website first because they have a very thoughtful and well-spelled out discussion. It turns out that sunscreen does block the production of vitamin D, but not completely. In this excellent article by Dr. Gilchrest from Boston University School of Medicine, she reviews the (fairly limited) research on sun exposure and Vitamin D. Here is what she concludes with regard to sunscreen usage:

"Although some have claimed that sunscreens block all UV and hence all Vitamin D photosynthesis, this is not the case. By definition, sunscreens allow continuous transmission of a fraction of erythemogenically weighted incident UV photons equal to 1/SPF or the total (eg. 1/15th or 7% for an SPF 15 product). Moreover, studies have shown that sunscreen users customarily apply half or less of the FDA-stipulated amount of product required to generate the stated level of protection (2mg/cm2) and hence achieve far less protection. If persons require 2-8 minutes of unprotected summer sun exposure to optimize cutaneous vitamin D synthesis, they could accomplish this in 10-20 minutes of exposure after apply an SPF 15-30 sunscreen in the customary manner. Most critically, regardless of one's complexion or extent of UV exposure, daily oral vitamin D supplementation can completely compensate for lack of cutaneous vitamin D photosynthesis [emphasis added]."

So what to make of all this? Yes, Vitamin D comes from the sun (hence the adorable moniker "the sunshine vitamin"). Yes, if you wear sunscreen, it does block the production of Vitamin D. Also, if you limit your sun exposure, or happen to live in a Northern latitude, or have a dark skin tone, you are even less likely to have opportunities to make Vitamin D. But the good news is that Vitamin D from a supplement is equally effective and unlikely to cause the lasting damage that we know the sun can.

The question of how much Vitamin D a person needs to take is not entirely settled, but U.S. public health authorities recommend a minimum of 200 IU (5 micrograms) daily for healthy adults. However, in light of increasing evidence suggesting benefit from higher doses of Vitamin D supplementation, some authorities recommend doses closer to 800 IU daily. And, just in case you were wondering how much is too much, the Institute of Medicine has defined the "tolerable upper intake level" for vitamin D as 2000 IU daily. Food sources for Vitamin D are unfortunately fairly limited, with oily fish like salmon or tuna being your best bet.

So before you decide to throw away the sunblock and run out there to catch some rays in the name of Vitamin D, it makes sense to weight the risks and benefits of getting vitamin D from the sun vs. the other things that you can get from the sun like cancer, wrinkles, sun spots, discoloration, sagging and more wrinkles. Especially because you can get vitamin D from a supplement and there is no supplement to take away wrinkles or cancer, despite what some cosmetics companies would like you to believe.

Cartoon courtesy of Natalie Dee.



BeautyTalk said...

I'd rather get my vit. D from a supplement. But have you heard of topical products with vitamin D? I wonder how effective they are... or if they are at all effective...

May 17, 2009 at 6:11 AM
Kyl said...

I agree on the supplement idea. I'm not familiar with any topical treatments, but maybe I'll check that out. Thanks for the comment!
May 17, 2009 at 12:11 PM

Meilily said...

Thanks for the informative article! I've also looked into the benefits of Vitamin D, and found some research that indicates it is related to good upper respiratory heath too! So, it is definitely something I consider when applying spf (blocking Vitamin D production). Though I probably don't apply nearly enough sunscreen, as suggested by Dr. Gilchrest, to have to worry.

May 17, 2009 at 4:55 PM
Kyl said...

Hi Meilily:

Thanks for the comment! The amount of sunscreen that they recommend applying is completely outrageous! I can't imagine my skin absorbing all of that excess. I should try it some time, just to see what happens.
May 17, 2009 at 7:06 PM

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