Endocrine Abstracts

Background: The GH-IGF system plays an important role in strength gain. Some studies suggest that Zinc, Magnesium and Pyridoxine (ZMA) supplementation could increase GH/IGF and testosterone levels in young subjects. This hypothetical increase could lead to significant changes in body composition. ZMA is a very popular supplement, easily found in specialty stores, and it is presumed to increase GH, IGF-I and testosterone levels. However, studies are divergent regarding its efficacy.

Aim: The present study aimed to verify the effects of physical training associated with 8-week ZMA supplementation on the IGF-I, IGFBP-3 and testosterone levels in young males.

Methods: Eighteen healthy male amateur American football players aged 18–25 years with at least 1 year experience in this sport modality were included in the study and followed during 8 weeks of training. The training consisted of a 90 min-conditioning session based on strength and aerobic exercises twice a week and specific tactic training also twice a week in different days. Energy intake and diet composition were determined by nutritionist. It was a double-blind study and the subjects were divided into two groups: ZMA and placebo groups according to the supplementation received. Anthropometric evaluation and blood sampling, for serum IGF-I, IGFBP-3 and testosterone determination, were performed at two different moments: at the beginning (M1) and after 8 weeks of supplementation (M2).

Results: Serum IGF-I and IGFBP-3 concentrations were higher at M2 in both groups. The increase was similar in the ZMA and in the placebo group. Testosterone concentrations were also higher at M2 than at M1 in a similar degree in both groups. The changes in anthropometric parameters that indicate lean mass gain or body fat mass reduction were similar in both groups.

Conclusion: The findings suggest that extra doses of the micronutrients present in the ZMA do not bring any additional benefits, either in the body composition or in the hormonal levels in subjects under adequate diet. Testosterone increase could partially explain the change in IGF-I and IGFBP-3.