Shining sunlight on vitamin D’s benefits

The New York Times recently ran a story indicating that a prominent physician scientist particularly associated with advocacy for vitamin D supplementation may have important conflicts of interest. The case is made that this doctor has promoted sales of vitamin D, testing for vitamin D and even the use of tanning salons through his influence on peers and the public. He has, in turn, been richly compensated by companies that make and sell supplements, perform tests or offer tanning beds.

I favor vitamin D supplementation (in general) despite no familiarity with the advocacy of this particular doctor and despite relying on more cautious and reliably unbiased sources. For me, this is a story about both scandal and sunlight.

Let’s start with scandal. Yes, at this point, the protagonist in the New York Time’s story (by Kaiser Health News writer Liz Szabo) has reportedly made quite a bit of money from his vitamin D advocacy. That could mean he is biased and driven by ulterior motives. But it doesn’t necessarily mean any of that.

I found peer-reviewed publications on vitamin D by the impugned physician going back 48 years. His industry funding goes back not nearly so far. So, there is an alternative, plausible narrative: A researcher devoted to the study of vitamin D became convinced of widespread deficiency and the importance of redressing it. As he became prominent over the years, so did his advocacy, based on his own research and that of others. As his advocacy became prominent, it caught the attention of industry elements. Eventually, they came along to say: “Your message benefits our bottom line, so we would like to support it, and you. We can help amplify your message with money; you don’t need to change what you were already saying.” And then… here we are.

This narrative does not entirely eliminate concerns about conflict. Someone with significant funding from specific industry elements should not be involved in drafting impartial, national guidelines with direct implications for those patrons. But before over-interpreting the implications of scandal, we should all pause to consider that this doctor’s advocacy may be honest, based on his view of the evidence, and just what it was before any money was involved. As for Al Gore, conviction and advocacy may have, and seemingly did, come first; an exchange of dollars only late in the game.

Which leads to sunlight, where contaminated conclusions about vitamin D may most reliably be disinfected. Vitamin D is not really a nutrient; it is a hormone. Under the native conditions to which our species is adapted, we don’t need vitamin D from food. Rather, we make it from sunlight. Dark skin, the original condition of our common ancestors, protects against intense, equatorial sun, while allowing for adequate vitamin D production to foster healthy growth and development.

When our ancestors migrated out of Africa, away from the equator, and into fewer hours of less intense sunlight, dark skin no longer reliably made enough vitamin D. A mutation favoring skin pallor was advantageous under those conditions, and we see the effects to this day. The most famously lightskinned peoples — Irish, Scandinavians — come from either far northern climes or from under frequent cloud cover, if not both. Vitamin D, quite simply, is why any of us is white. That says something about the profound reverberations of this compound through our physiology, where it controls calcium absorption and skeletal development, but also influences energy metabolism, immune function and much more.

Paleo-anthropologists estimate that our native levels of vitamin D were higher than we tend to see in modern populations, based on what we know about levels achieved by populations living outdoors with frequent sun exposure. If we use adaptation as our default, supplementation is warranted simply to approximate the levels native to our kind. So, I favor judicious supplementation. As for testing, I generally need a reason, such as unexplained symptoms, or unexplained bone thinning.

We all have reason to care about vitamin D, no further away than the surface of our own skin. It may well be that popular narrative and professional discourse on the topic are now home to the contaminants of bias and conflict. Confusion tends to dissipate, and reasonable conclusions reveal themselves, however, if we avoid a rush to judgment, and examine the whole story under the bright light of day.