Background: Zinc is an essential micronutrient to human physiology, and has many vital roles in physical exertion. It is understood that athletes have increased dietary requirements to support their physical training. However, there is a lack of evidence focusing on zinc status in athletes to establish whether zinc deficiency is a common issue of concern.
Aims: The aim of this research project is to undertake a systematic review of the zinc status of athletes (aerobic, anaerobic, or a combination) compared to healthy non-athletes aged 18 to 65 years. The studies must be cross-sectional and assess at least one zinc biomarker.
Design: Keywords and phrases were entered into PubMed, Scopus, SPORTDiscus, and the Cochrane Library. After removal of duplicates, all citation title and abstracts were screened for eligibility. The final data from the included literature was extracted and interpreted.
Results: Sixteen studies were eligible for inclusion. Fifteen out of nineteen athletic groups had lower plasma zinc concentrations compared to non-athletes. Twelve out of 15 athletic groups had higher dietary zinc intakes compared to non-athletes. There was no obvious relationship between dietary zinc intake and plasma zinc concentration in athletes, but this does not exclude other factors affecting athletes zinc status compared to non-athletes.
Conclusion: Plasma zinc concentration appears to be independent of dietary zinc intake in athletes, however, losses in sweat and urinary excretion may impact the zinc status of athletes. This review does not explain the implications zinc deficiency may have on athletic performance, nor does it describe how a zinc deficiency may exist in the absence of signs and symptoms. The main barrier to this lack of evidence is the absence of a single, robust zinc biomarker with internationally defined reference ranges.
