Vitamin D is essential for a healthy body, in particular, strong bones. The sunlight-bone link was recognized nearly 200 years ago, when dark, smoky skies in newly industrialized cities in England led to an epidemic of rickets: weak and deformed bones, especially in children. In the 1920s, the vitamin D link was further established when German chemist Adolf Windaus figured out that high-energy ultraviolet rays (UVB) in sunlight leads to the body synthesizing vitamin D — for which he got a Nobel Prize. (Strictly speaking, "vitamin" D isn't, since vitamins are organic molecules needed for survival and but not produced naturally by the body.) The main function of vitamin D is to allow our bodies to absorb essential calcium, magnesium and phosphate needed for healthy bones.
When most people spent much of their lives outside — hunting, farming, foraging — they got plenty of vitamin D from sunlight. It's available in a few foods, too, like fish but, historically, we've gotten all we need by simply being outside. Until a few years ago, that is, when we were abruptly told, "vitamin D deficiency is common in all age groups." The quote is from Boston University endocrinologist Michael Holick, who led the charge to compensate for what he called "a vitamin D deficiency epidemic."
In 2011, Holick was the chairman of the Endocrine Society's guideline writing committee when it established what, in retrospect, were unrealistically high vitamin D levels that effectively labeled 80 percent of the population as deficient. The society's extreme guidelines led to billion-dollar-a-year boom times for the vitamin D supplement and testing industry, not forgetting tanning beds. (Holick advocated the moderate use of tanning beds as a "recommended source" of vitamin D, despite their classification as carcinogenic by the International Agency for Research on Cancer in 2009.)
About the same time as the Endocrine Society recommendations, the National Academy of Medicine (then called the Institute of Medicine) issued a 1,132-page report saying that beyond 16 nanograms/milliliter (the way vitamin D in blood is measured), there were no bone-strengthening effects. Several IOM members later published an article in the New England Journal of Medicine saying that a more reasonable cutoff would be 12.5 ng/ml. Fewer than 6 percent of Americans have less than this level. In contrast, the Endocrine Society's guidelines categorized anything less than 20 ng/ml as "deficiency" and 21-29 ng/ml as "insufficiency," with a recommendation of 40-60 ng/ml for adults and children. Although he denies it, the fact that Holick received more than $100,000 from companies making vitamin D supplements and tests may have influenced his immoderate views. (A New York Times article, "Vitamin D, the Sunshine Supplement, Has Shadowy Money Behind It," Aug 18, 2018, makes for disturbing reading.)
The Endocrine Society is currently updating its guidelines for vitamin D guidelines. The methodologist on the committee, Christopher McCartney of the University of Virginia School of Medicine, told Scientific American, "Our conflict-of-interest policy is much more transparent and rigorous than I think it has been in the past." Which, hopefully, is bad news if you happen to be in the vitamin D manufacturing or testing industry.
Next week, I'll review the observational studies that led to the myth of vitamin D being a wonder "drug," and how it since lost much of its luster.
Barry Evans (he/him, barryevans9@yahoo.com) wonders how someone with financial ties to the vitamin D industry could have led an influential committee that classified 94 percent of us deficient in the vitamin.