It’s spring, which means lots of sneezing, sweets, and sunlight! Of those three, sunlight is probably the healthiest, so let’s shine a light on what sunlight does in the body and why we need it. First, the sun is vital for keeping the planet habitable. Without the sun, we would all die very fast as oxygen would solidify on the surface, and we’d be unable to breathe. Beyond being vital to life, sunlight is used by the skin to produce Vitamin D!

Vitamin D is actually a collection of very similar molecules called calciferols. These are fat-soluble steroid hormones that are used throughout the body. Vitamin D deficiency is a worldwide problem, and affects at least ⅓ of Americans. It is linked to complications in bones, kidneys, heart, and brain, as well as to diabetes, immune system issues, obesity, and poor pregnancy outcomes. Though indications of this deficiency seem robust, the solutions are anything but. Unfortunately, the effects of supplemental vitamin D, and therefore sunlight, are grossly understudied. Trial after trial after trial (check the extensive references list) shows that supplemental vitamin D – and in some cases supplemental light – does not have a significant effect on measurable outcomes for patients. These trials consistently find that the levels of circulating vitamin D in the bloodstream are increased, but symptoms are unaffected. The only results I could find from randomized, placebo-controlled clinical trials showing actual benefits to patients were for those with sickle-cell disease and in reducing respiratory infections in elderly patients.

This is counter to “common knowledge” and to the assumed knowledge found in several research papers. Observational studies, where scientists look at populations, find a myriad of problems associated with vitamin D and sunlight deficiency. Let’s try to illuminate why clinical trials haven’t found benefits when giving supplemental vitamin D. The answer is likely that the problems that cause vitamin D deficiency aren’t solved by supplementation! Vitamin D production starts in the skin, then goes to the liver and kidneys before the body can use it. The symptoms associated with low levels of vitamin D may not improve if there are underlying liver or kidney issues, though those conditions can hinder the production of Vitamin D.

Further, observational studies look at a population and investigate the correlations between items. This can tell us things that may be associated with each other but does not indicate that one thing is causing the other. An example would be looking at the availability of toilet paper and used car prices over the last 10 years. In 2020 toilet paper was unavailable and used car prices soared! This wasn’t because we needed toilet paper to run our used cars or anything; there was a pandemic disrupting supply chains! In the case of vitamin D deficiency, the lack of vitamin D is probably the effect of not going outside! If a mental disorder like depression keeps people indoors, this would lower the vitamin D they produce, not the other way around. On top of this, it is very difficult for scientists to isolate sunlight (and therefore vitamin D) from exercise. People who stay inside and never see the sun are, on average, less active. This can lead to some of the problems we associate with vitamin D deficiency, including bone issues, obesity, diabetes, and heart problems. In these cases vitamin D deficiency is more a canary in the coal mine than the smoke of a fire.

So, what can we take away from this? First and most importantly is that in all of these clinical trials supplemental vitamin D has been found to be safe. If vitamin D helps you with an issue, there is nothing wrong with continuing your care. Always consult with your doctor before making changes to your medication. Second, clinical trials are vital to our medical system! Observational studies are no substitute for actual experimentation in a placebo-controlled, randomized trial. The common knowledge is that sunlight and vitamin D are good for us. This is true, but it’s best to start at the source, the sun (if you can), rather than supplementing after the fact. We should spend more time outside in the nice weather, but remember your sunscreen.

Staff Writer / Editor Benton Lowey-Ball, BS, BFA

References:

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