Wednesday, July 6, 2011

Rodent Study Suggests: Selenium, Nature's Neuronal Corrosion Inhibitor Could Protect the Brains of Hard Training Athletes from Oxidative Damage.

Image 1: Selenium is a naturally occurring mineral
involved in a host of metabolic processes.
Are you a hard training athlete? A weekend warrior? Marathon runner? Or just an an average fitness-enthusiast? Yes? Did you ever think about what an exhausting workout, let alone arduous marathon running may do to your brain? No? Then it may come as a surprise to you that other than regular moderate physical exercise, which has repeatedly been shown to exert beneficial effects on mental and physical development, intense exercise precipitates oxidative stress not only in the working muscle groups, but within your whole body - including your brain, where the exercise-induced increase in free-radicals may dramatically increase lipid oxidation (Goldfarb.1996; Kanter. 1998).

Based on observations with other antioxidants and the well-established involvement of selenium in the activation of the master-antioxidant glutathion, researchers from the Selcuk University in Konya, Turkey, hypothesized that supplementation with yet to be determined amounts of selenium might ameliorate the detrimental effects of arduous exercise (Akil. 2011). To verify their hypothesis, the Akil et al. subjected a group of 4-6 month old Sprague-Dawley rats to one out of four treatments for 4 weeks:
  • group 1: unsupplemented sedentary control
  • group 2: selenium supplemented, sedentary control
  • group 3: swimming control (30 minutes in a closed glass-swimming pool; 50x50cm)
  • group 4: selenium supplemented + swimming (same as group 3)
Both, the animals in group 2 and group 4 were supplemented with additional  0.6mg/kg of selenium selenite per day. For an 80kg adult human being the human equivalent dose of 0.098mg or 90mcg per kilogram of body weight would amount to 7.8mg of additional selenium per day, a dose, of which textbook knowledge tells us that it is way beyond the upper-limit of 0.8mg/day. Yet, for the rats, this supposedly toxic amount of selenium turned out to be quite beneficial.
For more on the beneficial effects high doses of selenium may have and a short discussion of toxicity issues, see my previous post on "NAC + Zinc + Selen = Silver Bullett Against Mercury Poisoning"
As the data in figure 1 shows, the non-supplemented arduously exercising rats (group 3) had by far the highest malondialdehyde (MDA is an accepted marker of unwanted oxidation) levels. On the other hand, the MDA levels of the supplemented group were reduced by 11%. Compared to the sedentary controls, which had identical (i.e. within the statistical margin) MDA levels, the malondialdehyde content of their brains was still elevated by 57%. While selenium supplementation may thus have ameliorated the increase in brain MDA levels, it was not able to completely protect the rat-brains from free-radical induced oxidation processes.
Figure 1: Malondealdehyde (MDA) and glutathione levels in rat brains after 30 minutes of exhaustive swimming exercise (data adapted from Akil. 2011)
Interestingly, in both, the supplemented, as well as the non-supplemented exercise groups brain glutathion levels (GSH) increased by 124% and 71%, respectively - probably to protect the brain from extensive oxidation. Under this assumption the selenium induced increase in glutathione levels, which lead to a 53% greater GSH increase in the brains of the rats in the selenium supplemented swimming group, would adequately explain the lower MDA levels of the high selenium group.

While it would have been nice to see a comparison of the effects of different doses and exercise protocols, the study at hand is just another hint a the importance of a mineral, that was believed to be toxic up to the late 1950. Consequently, this is neither the first, nor will it be the last time you read about this extraordinary mineral on the SuppVersity - stay tuned for more!