Exercise in Glucose-6-Phosphate Dehydrogenase Deficiency: Harmful or Harmless? A Narrative Review

OBJECTIVES: Glucose-6-phosphate dehydrogenase (G6PD) deficiency, theoretically, renders red blood cells (RBC) susceptible to oxidative stress. G6PD deficiency has also been found in other types of cells than RBC, such as leukocytes and myocytes, where an inefficient protection against oxidative stress may occur too. Glutathione (GSH), a significant antioxidant molecule, levels are lower in G6PD individuals, and theoretically, the probability of oxidative stress and haemolysis due to exercise in individuals with G6PD deficiency is increased, whereas dietary supplementation with antioxidants may have beneficial effects on various aspects of this enzymopathy. METHODS: A search of the available literature was conducted using the keywords glucose-6-phosphate dehydrogenase (G6PD), deficiency, disease, exercise, muscle, antioxidant, vitamin, supplement, and supplementation. The search was limited to publications in English, conducted on humans, and published until August 2018. After screening, only relevant articles were included. RESULTS: There is little evidence indicating that G6PD deficiency can cause perturbations in redox status, haemolysis, and clinical symptoms such as fatigability and myoglobinuria, especially after intense exercise, compared to individuals with normal enzyme levels. CONCLUSIONS: Exercise could be used by G6PD-deficient individuals as a tool to improve their quality of life. However, there is a lack of training studies, and assessment of the effects of regular and systematic exercise in G6PD-deficient individuals is warranted. Finally, since GSH levels are lower in G6PD deficiency, it would be interesting to examine the effects of antioxidant or cysteine donor supplements on redox status after exercise in these individuals.