8 Weeks of 5mg/kg Zinc-Sulfate Fire Up Immune System of Turkish Wrestlers

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.

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.

Absurd: Will Supplemental Zinc Gluconate Deplete Your Zinc Levels?

Normally, I restrict myself to very recent studies, but the results of this 2007 (Tompkins. 2007) study on the bioavailability of zinc-enriched yeast and zinc gluconate in healthy volunteers that recently resurfaced on the Mind&Muscle boards, is too counter-intuitive and, if not scientifically flawed, important not to make it into the news.

In the study, which used a randomized, two-way crossover design, the volunteers were randomly assigned in groups of three to consume a single dose of either 20 mg of total Zn in the form of Zn gluconate or Zn yeast with 150 ml of water, after that urine, blood, and fecal samples were collected and analyzed over a 48-h period. The results were surprising, while "Zinc gluconate gave higher Zn concentrations in the blood in the first 6 h" it did not only show greater loss in the feces, but ...

the net Zn balance after 48 h for Zn yeast was 9.46 but for Zn gluconate it was -2.00, indicating that Zn gluconate supplementation contributed to a net loss of Zn.

As far as the reasons for this observations are concerned, the scientists speculate:

Presumably, this “extra” Zn lost was released from the body’s store of Zn metallothionein; however, we do not have any evidence of the source of the Zn material. This may suggest that the Zn salts stimulated a Zn detoxification pathway.

If this were true and the results are not biased by the background of the Institut Rosell, which is obviously financed by Lallemand Inc. who produce (pro-)biotic products (i.e. yeast based products), you might want to reconsider your own supplementation practices. The high doses of Zn Salts commonly used by bodybuilders and fitness enthusiasts (many suggest >50mg Zinc per day) may in fact lead your body to believe he becomes intoxicated with zinc. It is then a very natural reaction to excrete zinc and as the data from this study shows, this "excess" zinc (i.e. more zinc than you supplied) must - at least in parts - stem from zinc stores somewhere in your body.