Vitamin D Levels and Muscle Strength

Vitamin D Status and Muscle Function in Post-Menarchal Adolescent Girls

This study, published in The Journal of Clinical Endocrinology and Metabolism, showed that--in a group of 12-14 y/o girls living in the UK--greater muscle strength was associated with higher vitamin D levels.

I start with this study to make a few initial points on my first blog: first, this is an observational study, and not a clinical trial; in other words, they did not divide the girls randomly into two groups and--in a blinded fashion--give one group vitamin D and the other a placebo and see if there was a difference in muscle strength.

What they did was measure the vitamin D levels and muscle strength in all the girls and see if there was a correlation. And, they found one.

But, does this association mean that the lower vitamin D levels led to relative weakness? No...it does not. Association does not equal causality, and this is a common mistake made when one draws conclusions from this type of research. For example, this could mean that the girls with the greatest strength and highest vitamin D levels were outdoors more and thus were exposed to more sunlight, yielding higher vitamin D levels.

One other point: vitamin D has several functions aside from the well-known calcium absorption and bone-building/maintenance functions (e.g., immune, cardiovascular, muscular). The dermatologists have scared the heck out of us and turned many people (mainly women) away from even the occasional ray of sun (they react to the sun as if they were vampires).

Vitmain D deficiency is quite widespread and it would be a terrific idea to get between 10 and 15 minutes of direct sunlight before smearing on the sunblock with an SPF of 45. Please folks: GET SOME VITAMIN D!! This is especially true for darker complected people (African Americans, for example) who should think of supplementation.

I will have more to say about vitamin D and health in the future.

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