Animal study: 1000 IU vitamin D3 inhibits muscle breakdown in athletes
If athletes take a dose of about 1000 units of vitamin D3 daily, they recover more quickly from training sessions and may also build up muscle mass and strength more quickly. At least, that's what you'd expect after reading the animal study that Korean nutritionists at Sungshin Women's University published in Cytokine. Vitamin D supplementation inhibits the first step in the process of muscle breakdown after heavy exertion.
Does a vitamin D deficiency – which is found more often than not in the inhabitants of northern climes – have negative consequences for athletes? Yes it does, sports scientists at the University of Wyoming conclude after studying 19 well-trained endurance athletes. [Open Access J Sports Med 2012;3:35–42.] The more vitamin D3 in the athletes' blood, the less TNF-alpha the researchers found.
TNF-alpha is an inflammatory protein. In small quantities it plays a crucial role in muscle recovery; in high concentrations it inhibits the effect of anabolic factors in muscle cells and stimulates muscle breakdown.
These and similar findings gave the Koreans the idea of studying the effect of vitamin D supplementation by doing fundamental research in an animal study. For a period of eight weeks the researchers trained a group of rats: they ran for 30-minute sessions on a treadmill five days a week. The researchers gradually increased the intensity of the animals' exertions. And a control group did not run.
Half of the rats that did training had 25 micrograms vitamin D3 injected into their small intestine daily [HED]. The human equivalent of this dose would be about 1000 IE per day. The other half were not given any vitamins [HE].
In the rats that were given vitamin D3 the concentration of the enzymes LDH and CK in blood of the HED rats rose by less than in the HE rats. LDH and CK are indicators of muscle breakdown.
Vitamin D administration inhibited the rise in production of the inflammatory proteins TNF-alpha and interleukin-6 in the HED rats in relation to the animals in the HE group. The Koreans discovered that vitamin D3 supplementation reduced the action of the transcription factor NF-kB. NF-kB activity is the very first sign of muscle breakdown.
"Therefore, supplementation with vitamin D3 may be beneficial in the rapid recovery or in protecting muscle damage from consistent training", the Koreans conclude.
Cytokine. 2013 Jul;63(1):27-35.
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