|If we were all training at "Muscle Beach", we would probably not need any vitamin D3 caps to get our 25(OH)D levels into the recovery friendly 50ng/ml zone. They would already be there!|
- "Vitamin D Builds Muscle: 70% Reduction in Myostatin, 45% Increase in Myotube Size in 10 Days" | learn more
- "Leucine, Insulin & Vitamin D*: A Hypertrophy Boosting Triplet That Does Not Make It From the Dish to the Gym?" | read more
The title does yet not "say it all". Moreover, what it doesn't tell you is the most important piece of information. The study period was short (35 days) the dose of vitamin D was relatively high (4,000IU) was conducted with "reportedly healthy and modestly active (30 minute of continuous physical activity at least 3 time/week) adult men with low, albeit normal vitamin D levels (25(OH)D ~ 30ng/ml)! The otherwise almost obligatory question about the potential relevance in "normal" human beings does thus become superfluous - and this is true for all the observations the scientists made, i.e.
- ... the linear relationship between baseline 25(OH)D levels and the increase in serum vitamin D in response to the with an up to 150% increase in subjects in the deficiency zone and less than 50% increases in subjects in the >40ng/ml range, ...
- ... the steady serum calcium levels, which make concerns about potentially kidney damaging increases in calcium from vitamin D3 supplementation obsolete, ...
For the researchers this is a model of a "muscle damaging event" (P< 0.05; ≈8% at 24-h), which was, as it was to be expected, associated with an increase in the circulating levels of the "liver enzymes" alanine (ALT) and aspartate (AST) aminotransferase, of which many medical textbook will tell incorrectly tell you that they would indicate a strain on the liver / liver damage, when they are actually only markers of increase amino acid catabolism. The attenuation (P< 0.05) of the immediate and delayed (48-h, 72-h, or 168-h) increase in these enzymes in the vitamin D supplemented group is thus an indicator of "muscle protective" or at least general protein sparing effects of supplementally increased vitamin D levels.
|Figure 1: Strength recovery (%) from immediately post to 24 post workout, left; serum ALT values immediately after, 24h, 72h, and 168h after the exercise test (Barker. 2013).|
- Barker, T., Schneider, E. D., Dixon, B. M., Henriksen, V. T., & Weaver, L. K. (2013). Supplemental vitamin D enhances the recovery in peak isometric force shortly after intense exercise. Nutrition & Metabolism, 10(1), 69.