Sunlight and Vitamin D; More Complicated than We Thought?

I admit have fallen into a bad habit when it comes to vitamin D.  I have exchanged the benefits of sunlight for vitamin D supplementation.  Turns out I may be mistaken.

This is not to say that vitamin D, by itself, does not have a long list of benefits and has not been associated with pretty much every chronic disease you can think of, because it has.

But somewhere along the way I thought we could have our cake and eat it, too.  Don’t worry about sun exposure and basal cell and squamous cell skin cancers–just take vitamin D instead and you’ll get all the same beneifts.  (You’ll notice I didn’t throw in melanoma–the relationships between melanoma and sun exposure are not exactly clear-cut, despite what most people think).

But, just like everything else that has to do with the way our bodies are built and the way we interact with our environment, the story is always far, far more complex.  Beyond vitamin D production in the epidermis, what about that first sensation of warmth you get after walking out in the sun from a cold building?  Or sitting in a lawn chair in the spring feeling the sun on your skin?  (This of course does not apply here in Arizona in July, in which case you would be burnt to a crisp in about 8 minutes)

There is an emotional component to sun exposure that may go beyond anything we can really measure accurately.  This can never be replaced by vitamin D supplementation.

So why all this philosophizing?  It has to do with this particular article.  In this mouse study researchers looked at the effects of sunlight on multiple diabetes risk factors (weight gain, glucose intolerance, insulin resistance, nonalcoholic fatty liver disease measures and blood levels of fasting insulin, glucose, and cholesterol).  What was interesting is that these same benefits were not all seen when vitamin D supplementation was used instead of sun exposure.  Clearly this indicates that sunlight has benefits above and beyond its ability to help your body produce vitamin D.

So what gives?

Turns out that sunlight (specifically UVA) leads to the production of the compound nitric oxide (NO) in the skin.  While small, NO is a pretty unique little compound that has a commendable list of biological effects.  On the top of the list is its ability to lower blood pressure.  The decades-long search for this compound (originally termed “endothelial derived relaxation factor) led to the awarding of the Nobel Prize in medicine in 1998 to Drs Furchgott, Ignarro and Murad.

While NO is not the end-all-and-be-all of anti-diabetes molecules found in our bodies, it certainly does play a role.  This is the reason why the market for arginine-based products was created (our bodies use arginine to make more NO).  However, I personally think that adding more NO to the equation does not overcome a pro-diabetic lifestyle and the long-term studies looking at arginine supplementation bear this out.

This does not mean that using rationale sunlight exposure as a tool in the toolbox to help combat diabetes is a bad idea.  Quite the opposite.  I think that sunlight exposure should be a part of a healthy lifestyle, not just for vitamin D production but also for the psychological effects and the NO effects on diabetes as well.

Remember that next time you slap on SPF-80 and run to the car under a black umbrella…


James Bogash

For more than a decade, Dr. Bogash has stayed current with the medical literature as it relates to physiology, disease prevention and disease management. He uses his knowledge to educate patients, the community and cyberspace on the best way to avoid and / or manage chronic diseases using lifestyle and targeted supplementation.