The effects of dietary protein supplementation on exercise-induced inflammation and oxidative stress: a systematic review of human trials

This systematic review examined the effects of whole protein and commonly consumed amino acid supplements on markers of exercise-induced inflammation and oxidative stress and was reported according to the PRISMA guidelines. MEDLINE and SPORTDiscus were searched from inception until June 2021. The inclusion criteria were randomized clinical trials in humans, healthy adult participants (≥18 years), dietary protein/amino acid interventions, and measurements of oxidative stress/the redox status or inflammation post-exercise. The Cochrane Collaboration risk of bias 2 tool was used to critically appraise the studies. Data extracted from thirty-four studies were included in the systematic review (totaling 757 participants with only 10 females; age range 19–40 years). The included trials examined five types of whole protein and seven different amino acids supplements; most studies (n = 20) failed to identify statistically significant effects on markers of inflammation or oxidative stress after exercise; some (n = 14) showed either anti-inflammatory or antioxidant effects on some, but not all, markers. In conclusion, we found weak and inconsistent evidence that dietary protein/amino acid interventions can modify exercise-induced changes in oxidative stress and inflammation. However, given that these were not the primary outcomes in many of the included studies and many had design limitations, further research is warranted (Open Science Framework registration number: 10.17605/OSF.IO/AGUR2)

Influence of biological sex on exercise-induced nuclear factor erythroid 2-related factor 2 and downstream targets

Objective: To evaluate whether exercise induces different nuclear factor erythroid 2-related factor 2 (NRF2) responses in males and females. Methods: 22 males and females (n=11 per group; mean [SD]: age: 25 [6] years, height: 1.71 [0.10] m, weight: 69.6 [12.3] kg) performed 100 drop jumps and 50 squat jumps. NRF2/antioxidant response element (ARE) binding in peripheral blood mononuclear cells, glutathione peroxidase (GPX) activity, and immune markers influenced by NRF2 (interleukin- 6 [IL-6], tumour necrosis factor-α [TNF-α], matrix metalloproteinase-9 [MMP-9], vascular cell adhesion molecule-1 [VCAM-1], total leukocytes, neutrophils, monocytes) were measured pre-, post-, and 1 h post-exercise. Results: NRF2/ARE binding did not significantly alter following exercise (p=0.59) and no sex differences were evident (p=0.17). Similarly, GPX activity did not change post-exercise (p=0.74) and did not differ between sexes (p=0.61). IL-6 and TNF-α did not increase post- exercise (p>0.05 for both) but were lower in females (p<0.01 for both). MMP-9 increased post-exercise (p=0.02), but no group differences were found (p=0.27). VCAM-1 was unchanged after exercise (p=0.38) and did not differ between groups (p=0.11). Total leukocytes, neutrophil, and monocytes all increased post-exercise (p<0.01 for all); neutrophils were lower (p<0.01), and monocytes higher (p=0.03) in females vs. males. Conclusion: There were no sex differences in NRF2 activity at rest and in response to an exercise bout, however, several immune markers displayed sex-specific differences, independent to NRF2. Significance: Sex differences in NRF2 signalling were not evident, suggesting males and females may incur similar redox-specific adaptations post-exercise.</p