SuppVersity - Nutrition and Exercise Science for Everyone

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 whethe...

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 glucona...

Zinc is probably among the most popular bodybuilding and fitness supplements on the market. Thus, it may interest you that a recent study by Wessels et al. ( Wessels. 2010 ) found that taking supplemental zinc will increase serum zinc levels within 5 days: We conducted a randomized, double-blind, placebo-controlled trial in 58 apparently healthy males aged 19–54 y. Participants received 1 of 3 liquid supplements daily for 21 d: 10 or 20 mg Zn/d, as Zn sulfate, or placebo. Fasting plasma Zn concentrations were measured on 14 occasions before, during, and after supplementation. [...] Controlling for baseline concentrations, plasma Zn concentrations were consistently elevated above baseline by d 5 among individuals in both of the Zn-supplemented groups compared with those receiving placebo supplements, regardless of their initial plasma Zn concentration. There were no significant group-wise differences between those who received either 10 or 20 mg/d Zn . Plasma Zn concentrat...