A Rare Win For Vitamin D Supplementation: Multiple Sclerosis

Randomized trials of Vitamin D supplementation almost always fail. Not this time.

Study after study, across diseases from Alzheimer’s to Zika virus, have shown that low vitamin D levels are risk factors for bad outcomes. Seriously, I challenge you to find a disease state where there isn’t at least some data suggesting worse outcomes among people with vitamin D deficiency.

And yet, when the inevitable randomized trial of Vitamin D supplementation comes around, you get… nothing. It’s become a bit of a running joke on this blog — the compelling observational data shut down by the definitive randomized trial.

So we have good data that low levels are associated with various problems, but a failure to show that correcting those levels makes a difference. The implication is simple: it’s the classic case of correlation vs. causation. Low vitamin D levels are simply correlated with bad outcomes, they don’t cause bad outcomes. It’s not actually the Vitamin D that is causing the problem — people who are sick for other reasons just happen to have low Vitamin D. I actually give a…