A recent study attempted to show that vitamin D supplementation doesn’t improve osteoarthritis of the knee. For this study, subjects with knee osteoarthritis took vitamin D for two years. Overall, the subjects didn’t experience any improvements in knee pain. And they didn’t reverse cartilage damage to their knees.
Of course, this news made headlines in USA Today and U.S. News & World Report. Heck, even Runner’s World reported on it for the benefit of all their pavement pounders.
But the study has several major flaws– any one of which would have normally made sure it never saw the light of day (if results had been positive!).
Thankfully, the Journal of the American Medical Association (JAMA) pointed out some of these flaws last month.
First of all, the original study lumped together patients who were vitamin D deficient with patients who had adequate levels. Those with the lowest levels actually did show improvement with supplementation. But the news outlets didn’t report on that.
The study also lumped together patients with light-to-moderate knee damage with patients who had severe damage to their knees.
As I’ve said before in my Insiders’ Cures newsletter, there comes a point where damage becomes too severe for the joints to heal themselves. At this point, you can’t expect to get help from any natural approach alone. Even from vitamin D.
In addition, the patients in the study took powerful non-steroidal anti-inflammatory drugs along with their vitamin D supplements. These drugs can overwhelm the effects of natural supplements.
The researchers didn’t consider this fact. Yet, giving potent drugs together with gentle nutrients is a frequent problem found in studies conducted by researchers unfamiliar with nutrition. Plus–as I discussed in my Insiders’ Cures newsletter–these researchers often conduct studies using the wrong doses. Most of the time, they use far too little of a nutrient.
But the biggest problem with this particular study? It was too small. They included just 146 patients! And this sample size simply isn’t large enough to have enough statistical power to draw any conclusions. Much less the right ones.
And once again, I’m struck with how low the subjects’ vitamin D levels were to begin with. (And even JAMA didn’t comment on it.)
For this study (and according to a great deal of other research), a vitamin D level of just 36 ng/mL is considered “sufficient.” Researchers presumably base this figure on government misguidance. But that’s barely at the margin of adequate health. And it certainly would not be considered a “therapeutic” level. You cannot reverse and repair years of bone and cartilage damage with levels this low.
JAMA does point out that many stronger studies over the years do support a key role for vitamin D in bone health. In fact, we have known about the link between factors related to vitamin D levels and bone health for two centuries. And one misguided, fatally flawed study certainly doesn’t change that.
1. JAMA. 2013;309(2):155-162. doi:10.1001/jama.2012.164487.
2. JAMA April 17, 2013, Vol. 309, No. 15, page 1583.