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07.04.2015

More vitamin D, more muscle mass

If you have an optimal amount of vitamin D in your blood – which surprisingly few people actually do – you'll have more muscle mass than if your vitamin D status is too low. Nutritionists at Mahidol University in Thailand concluded this from a small epidemiological study they did of 163 overweight but healthy men and women.

Study
The researchers measured the concentration of 25-hydroxyvitamin D in the subjects' blood and also measured their body composition using bioelectrical impedance analysis.

Results
Although Thailand is a tropical country with a lot of sunshine, most of the participants had relatively low vitamin D levels in their blood. The researchers had expected this.

Other epidemiological studies have shown that high fat mass is often accompanied by low vitamin D levels. [PLoS Med. 2013;10(2):e1001383.] One of the reasons for this is that as a body becomes fatter the skin surface area increases less than the mass does. The amount of sunlight that the skin can absorb – and with it the amount of vitamin D that the body can synthesise – doesn't increase as much as the person's weight increases.

And, as you'd expect, the researchers found that participants with higher levels of vitamin D in their blood were the ones who had a lower fat percentage.

A high vitamin D level was also associated with more muscle mass.

A high vitamin D level helps muscle building, the researchers suspect. In in-vitro studies where researchers expose muscle cells to vitamin D, the muscle cells produce less myostatin as a result. [J Steroid Biochem Mol Biol. 2013 Jan;133:1-11.] In addition, muscles cells that get too little vitamin D break down muscle proteins faster. [Endocrinology. 2013 Nov;154(11):4018-29.]

So, as far as the researchers can tell from their statistical calculations, more vitamin D means more muscle mass. The statistical calculations also showed that a large fat mass has a negative effect on muscle mass.

Conclusion
The research results imply that people might be able to improve their body composition by taking a vitamin D supplement. The researchers suggest that more research is needed to see whether this is indeed the case.

Source:
Nutrition. 2015 Jun;31(6):801-6.

More:
Animal study: 1000 IU vitamin D3 inhibits muscle breakdown in athletes 29.11.2013