This isn't the story you might think it is, from that title.
Rather, it's about how the medical community gets stuff wrong—and I’m not talking about two or three hundred years ago. It’s a much more recent story. It’s a story about how medical knowledge is always evolving, and like most things that are complex and unsettled, how mistakes are made and perpetuated, and how wrong information can assume a life of its own.
Twenty or so years ago, a new measure popped up on my annual blood test: “vitamin D.” The lab was now checking whether I had enough vitamin D circulating in my blood. It turned out that my level, while apparently not alarming, was nonetheless deemed “insufficient.” I should be taking vitamin D supplements, I was told. That seemed fine—vitamin D is relatively cheap and comes in small, easy-to-swallow capsules, and I didn’t think much of it.
I’m not sure how long it took before I discovered, to my surprise, that a lot of people I knew also had a vitamin D insufficiency. That of course set my skepticism gland tingling—especially as, at that time, I was living in sun-splashed South Florida, a place where the sun provides a plethora of free vitamin D. How were all these seemingly healthy people lacking in vitamin D?
Well, they weren’t.
An interesting story appeared in Scientific American a couple of years ago about how the medical community fatefully misinterpreted a vitamin D meta-study. I encourage you to read the full article. Again, this is Scientific American, a publication long known for rigorous, fact-based judgment, and not the National Enquirer.
Vitamin D supplements took on an other-worldly super pill aura in the early 2000s when, as the article tells us, “researchers began amassing a pile of studies suggesting that low vitamin D levels could be a factor in cancer, cardiovascular disease, dementia, depression, diabetes, autoimmune diseases, fractures, respiratory illnesses and Parkinson’s disease.”
One problem: the supposed benefits of taking extra vitamin D came from “observational” studies. Observational studies do not purport to show cause and effect. The author gives an example of say owning a Porsche and being wealthy. A lot of wealthy people own Porsches, but if I go out and buy one, that doesn’t mean it will make me wealthy.
In any event, a later study of 26,000 basically healthy adults, who took a hefty dose of vitamin D or a placebo for more than five years, showed vitamin D takers demonstrated none of the myriad benefits that had been touted. The vitamin didn’t help with cancer or heart disease, or “prevent falls, improve cognitive function, reduce atrial fibrillation, change body composition, reduce migraine frequency … reduce knee pain or even the risk of bone fractures.”
No Benefit Above 20 ng/ml
But the utterly fascinating part of the article, to me, concerns the birth of vitamin D-ism:
The belief that so many of us are deficient in vitamin D came from a misinterpretation of normal levels that the Institute of Medicine determined a decade and a half ago. Here’s what happened:
The institute had experts examine multiple studies of vitamin D and health. The committee concluded that the bone-strengthening benefits of vitamin D top out at 12 to 16 nanograms per milliliter, and there is no benefit to having a blood level above 20 ng/ml.
They noted that most people are just fine at 16 ng/ml!!!!
So how did we get to this point? Most of the population exceeds 20 ng/ml, and so should be in a “sufficient zone”—but instead is flagged with the “insufficiency” label between 21-29 ng/ml.
Well, 20 ng/ml was “erroneously interpreted by some health-care workers as the bare minimum, instead of a level marking good amounts for most people.” Then came a second set of guidelines, put out by another medical group, the Endocrine Society, which was looking at much of the same evidence that the institute used. But the Endocrine Society’s advice was “aimed at clinicians, particularly those caring for patients at risk for vitamin D deficiency.”
Plus, there was another interesting, um, wrinkle we’ll get to soon.
The Endocrine Society categorized anything under 20 ng/ml as “deficiency,” and 21 to 29 was “insufficiency.” Its guidelines were largely taken to mean that everyone needs a vitamin D level of at least 30 ng/ml.
But the Institute of Medicine pretty much said: “Whoa, not so fast.” It pushed back against the endocrine group’s conclusions. For example, the Endocrine Society used a study of only 34 people to claim that people with vitamin D levels above 30 ng/ml absorb calcium better. But it ignored a study of more than 300 people that “found that calcium absorption pretty much maxes out at vitamin D levels of 8 ng/ml.”
Hmm. Why?
‘A Religiosity Around Vitamin D’
Well, here’s that interesting wrinkle I just promised: the lead author of the society guidelines was an endocrinologist who has received at least $100,000 from companies that make vitamin D supplements and tests, journalists discovered. He is also a vitamin D promoter who wrote a book, “The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problems.” To be fair, he did deny to the magazine that he had conflicts of interest and said most of the money he received from the industry had nothing to do with vitamin D.
All that all may be true, but Upton Sinclair’s wise observation comes to mind: “It is difficult to get a man to understand something, when his salary depends upon his not understanding it.” Money—even small amounts—tends to influence us in subtle and not-so-subtle ways.
Now, a coda to the vitamin D story. My two children, 13 and 16, recently had blood tests. They both came back perfectly normal—except for one thing, the doctor said. Can you guess what?
“Insufficient level of vitamin D.”
I laughed when my wife told me this. Not much has changed, apparently. My healthy son and daughter are deemed to have insufficient levels of vitamin D, most likely because of a misinterpretation of an old study that, oddly, lives on and on.
Indeed, Scientific American informs us that more than 10 million vitamin D tests are done yearly in the United States, despite the fact that major medical organizations don’t recommend this mass-screening of the population. Why does it continue? There’s a telling quote in the article:
“There’s a religiosity around vitamin D.”
Ah. That I understand. As I’ve written about stretching and knee pain, it’s very hard to talk a stretching adherent out of this conviction that stretching is helpful for injured tissues, no matter the evidence. At some point a rational person has to realize, when talking to someone who belongs to the Church of Stretching: I’m not dealing with science-based people. I’m dealing with belief-based people.
With knee pain though, it’s often not a religiosity that you’ll be fighting against, but wrongheaded, entrenched thinking. It’ll be comments like these:
“Your knees just wear out and there's nothing you can do about it.” “Cartilage can’t heal.” “Your bad knees will just get worse.” “If you run long enough, your knees will fall apart.”
Wrong, wrong, wrong, wrong.
So if you get discouraged by your doctor’s pessimistic message about your knee pain, don’t feel bad. Remember, it looks like they got vitamin D wrong too.
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