Vitamin D Supplementation: of Scandal, Sunlight, and Skin in The Game

Vitamin D Supplementation: of Scandal, Sunlight, and Skin in The Game

David Katz 10/09/2018 5

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, an endocrinologist at Boston University, has personally contributed enormously to 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 at the receiving end of very considerable compensation from companies that make and sell supplements, perform tests, or offer tanning beds.

That any single individual, whatever their professional pedigree, should exert a major influence on widespread medical testing and practice is unusual. The story in this case contends, however, that prominence (the physician in question has published hundreds of peer-reviewed papers and has had a role in drafting official vitamin D guidelines) and proselytism have mingled with particular potency.

Be that as it may, 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, with a sidebar about the nature of scientific evidence and how we interpret it.

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

I recall the time when Al Gore was accused by political opponents of having conflicts of interest because he had investments in “green energy” companies. Gore convincingly responded with the obvious rebuttal: these critics were misconstruing cart for horse. In other words, Gore advocated for responses to climate change not to make money, but from deep conviction. He subsequently did just what we are all told people with real integrity do: put his money where his mouth was. He invested in companies that were doing the very things he was calling on industry to do. He was advancing the mission to which his devotion was already a matter of public record.

One of our problems in this age of rampant scandal is that we rush to judgment. Partisanship, propaganda, Internet echo chambers, and click-bait hyperbole all foster this. The days of reserved judgment are quaintly archaic now. But this is to the detriment of us all, because we are prone to be wrong in every extreme direction, never settling on more moderate truths.

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.

My position about scandal, then, is that we have more than our share of the real thing to deal with these days. The possibility of ulterior motives does not prove them, and even ulterior motives don’t necessarily disprove the conclusions. They are reasons for concern, and scrutiny, and we may credit the New York Times’ coverage for inviting that. But any given position is not safely correct simply because motives are pure, nor reliably incorrect just because motives are dubious. The “what” may be right, or wrong, independent of the “why.” 

Which leads to sunlight, where contaminated conclusions about vitamin D may most reliably be disinfected. As noted, I favor vitamin D supplementation with no vested interest* other than public health. My position derives from adaptation, and the proposition that we all very literally have skin in this game.

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 light-skinned 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.

Paleoanthropologists 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. I live in New England, work indoors, and get limited sun exposure much of the year. Accordingly, I take 2000 IU of vitamin D3 daily in winter; 1000 IU daily in summer; and skip it altogether during outdoor vacation time. I think dosing can and should be personalized to correspond with patterns of diet, lifestyle, and sun exposure. I advise against tanning beds, as I think the harms outweigh any potential vitamin D-related benefits.

As for testing, I generally need a reason. Reasons include any symptoms or signs of vitamin D deficiency, such as unexplained bone thinning; a specific patient request; a condition causing intestinal malabsorption; or kidney disease, which can interfere with activation of the vitamin D molecule (vitamin D is activated through sequential hydroxylation steps in the liver and kidney; don’t ask! Active vitamin D3 refers to the compound produced by these steps). But frankly, I think vitamin D testing is of far greater value than many of the measures in so-called “routine blood work,” which is in fact ordered as a matter of fairly futile routine. I think it is at least as reasonable to test vitamin D routinely as it is to test blood counts and blood chemistries, and perhaps a bit more so.

Finally, there is the matter of evidence. The New York Times reported the lack of clear benefit from vitamin D in randomized trials as damning. But absence of evidence is not evidence of absence. In other words, failing to show the decisive health benefits of a nutrient, or spinach, or blueberries, does not preclude such benefits. If we did for exercise what we do for diet, we would need to prove not that walking is good for health, but that any one particular step on a very long walk exerted an independent effect on health.

Consider that people who are robustly healthy, exercise routinely, get outdoors often, and eat an optimal and varied diet are least likely to have vitamin D deficiency, or to show any obvious response to vitamin D supplementation for the most obvious of reasons: you can’t fix what isn’t broken. At the other end of the scale, people prone to vitamin D deficiency in conjunction with ill health, poor diet, and lack of outdoor activity – are unlikely to get much better just from vitamin D. The isolated effect of any one piece of the whole lifestyle formula is very hard to demonstrate in a clinical trial because it tends to be very small, no matter what that piece is. When effects are real and relevant, but relatively small, uncommon, or both - truly massive (hundreds of thousands of participants) or massively long (decades) trials are needed to reveal them.  Smaller, shorter trials tend to show no particular effect, and neither prove nor disprove the absence of one.

Finally, nutrient supplementation in a generally healthy population may tend to take body levels of the substance from adequate to optimal, and do much the same for health. Randomized trials far less dependably discern a change in “overall vitality” than they do the presence or absence of some particular condition.

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.

*I serve as a science advisor to certain nutrient supplement manufacturers, but have no activity or interests related directly to vitamin D

Dr. Katz’ new book, The Truth about Food, is due out October, 2018- with all proceeds going to support The True Health Initiative. For more information, click here.

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  • Scott Chambers

    Blood tests have shown that my D3 levels were deficient, so I started taking 1 caplet per day, and now my levels are at the normal place.

  • Naeem Qiam

    Modern day humans are not outdoor creatures, we spend most time indoors.

  • Claire Louise

    My doctor told me I have a Vitamin D deficiency.. I literally only go outside when I have to go to work, maybe that's why..

  • Martin Finch

    Amazing! really proves that god is real. even a sun had other purpose for a reason.

  • Jude Irvine

    The sun is a natural ressource and in quite plentyful supply where we evolved.

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David Katz

Healthcare Expert

David L. Katz, MD, MPH, FACPM, FACP, FACLM, is the Founding Director (1998) of Yale University’s Yale-Griffin Prevention Research Center, and former President of the American College of Lifestyle Medicine. He has published roughly 200 scientific articles and textbook chapters, and 15 books to date, including multiple editions of leading textbooks in both preventive medicine, and nutrition. He has made important contributions in the areas of lifestyle interventions for health promotion; nutrient profiling; behavior modification; holistic care; and evidence-based medicine. David earned his BA degree from Dartmouth College (1984); his MD from the Albert Einstein College of Medicine (1988); and his MPH from the Yale University School of Public Health (1993). He completed sequential residency training in Internal Medicine, and Preventive Medicine/Public Health. He is a two-time diplomate of the American Board of Internal Medicine, and a board-certified specialist in Preventive Medicine/Public Health. He has received two Honorary Doctorates.

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