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03.05.2009


Athletes who take vitamin D perform better

Athletes – like the rest of humanity – could do to take extra vitamin D, and lots of it too. The amount of vitamin D that athletes get from their food, even if they take multi-vitamin supplements, is not enough for optimal performance, American researchers write in an article that will be published soon in Medicine & Science In Sports & Exercise.

Recent studies suggest that an optimal level of 25-hydroxy-vitamin D [structure shown below] is fifty to eighty nanograms per millilitre. This is the concentration that you find normally among inhabitants of sunny countries. Most Westerners have a much lower. According to the researchers this is because we spend far less time outside. We shut ourselves up in our caves of brick and concrete and spend most of the day
staring at computer screens. As a result we get far too little sunlight on our skin.

The UV radiation in sunlight converts vitamin D metabolites from our food into 25-hydroxy-vitamin D in our skin. This analogue is also what supplements contain, and is also found in animal products: vitamin D3. Salmon is a good source. The 25-hydroxy-vitamin D changes in the kidneys once again into 1,25-dihydroxycholecalciferol, the active vitamin D metabolite. An alternative to sunlight is therefore to take vitamin D3 supplements.

The intake of vitamin D3 among the general population is on the low side. The average American doesn’t manage more than three hundred units per day. Because supplements usually only contain small amounts of vitamin D, they don’t help much. There are old studies, however, which show that athletes perform better if their skin is exposed more often to UV light, and they therefore have more vitamin D3 in their blood.

In 1938 Russian researchers compared athletes who received UV radiation with those who did not. Both groups followed the same training programme. The UV athletes showed a progression of 7.4 percent, while the others only managed 1.7 percent. In 1944 German researchers did a similar kind of experiment with students. The students who received UV radiation treatment twice a week showed a performance improvement on the ergometer of 13 percent. The students who got no UV radiation showed no performance improvement.

There are no studies of power athletes’ performance with vitamin D3 supplements. Nevertheless, going by the other studies it’s possible to conclude that power athletes are likely to benefit from taking extra vitamin D3.

The figure below shows how the level of 25-hydroxy-vitamin D varies over the course of a year, according to a recent study.




Compare the curve above with the one in the graph below, which is from a German study done in the fifties, where the researchers got seven test subjects to train their lower arms. The graph shows their progression, which was highest when the concentration of 25-hydroxy-vitamin D in the blood was also at its highest.



The first author of the study, John Cannell, is the head of the Vitamin D Council [vitamindcouncil.org], an organisation that promotes the use of vitamin D supplements and is sponsored by Bio-Tech Pharmacal, a vitamin D3 supplements manufacturer. [bio-tech-pharm.com]

The Vitamin D Council believes that everyone who wants to be sure that they have enough 25-hydroxy-vitamin D in their blood should take five thousand units of vitamin D3 in the form of pills every day. That sounds like a lot. The strongest vitamin D supplements easily available only contain a thousand units per tablet. But, according to the Vitamin D Council site, it’s really not that much. "The skin produces approximately 20,000 IU vitamin D in response 20–30 minutes summer sun exposure."

After three months then you should of course really test whether your vitamin D level is high enough. Coincidentally, Cannell, just like his co-author Bruce Hollis, is a consultant for the DiaSorin Corporation, a company that makes tests for vitamin D in the blood. [diasorin.com]

In a recent Austrian study, elderly people became stronger when they took eight hundred units of vitamin D daily. Other researchers have discovered that taking vitamin D supplements extends life expectancy. High vitamin D levels delay molecular ageing.

Source:
Med Sci Sports Exerc. 2009 Apr 3. [Epub ahead of print].

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