Regular readers of this blog will have noticed that I am generally opposed to mega-dose supplementation with isolated nutrients and so I do not really know what to make of the results of a recent investigation (
Kara. 2011) into the effects of 5mg/kg bodyweight
zinc-sulfate on cytokine response in 15–17 year-old male subjects.
At the beginning of the study, there were no significant differences of the measured parameters between the four study groups. At the end of the study, the levels of TNF-α, IL-2, and IFN-γ were significantly higher in the two zinc-supplemented groups compared to those that did not receive supplementation, regardless of the activity status (p < 0.01).
Most interestingly, mega-dose (I do not really get, why the authors call 350mg
zinc, which would be the dose for a 70kg subject still "physiological")
zinc-sulfate supplementation elevated TNF-alpha, IL-2 and IFN-Gamma by >90% regardless of whether the subjects were active sportsmen or sedentary.
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| Figure 1: Serum IL-2 levels in the study groups (pg/ml) (Kara. 2011) |
Other than one might expect
zinc supplementation did thus not only blunt exercise induced reductions in immunity, but provoked an overall increase in cytokines which are associated to leukocyte (IL-2) and macrophage (IFN-Gamma) or both (TNF-alpha) activation. In view of the not yet fully understood involvement of these cytokines in metabolic and autoimmune diseases, the authors' conclusion that this "Physiological dose of zinc supplementation to athletes may be useful for sport health and nutrition" does yet appear to be premature.
