Influence of N-Acetylcysteine Supplementation on Physical Performance and Laboratory Biomarkers in Adult Males: A Systematic Review of Controlled Trials.

N-acetylcysteine (NAC) is used as a sports supplement for its ability to modulate exercise-induced oxidative damage through its antioxidant actions and maintenance of glutathione homeostasis, positioning NAC as a strategy to improve physical performance. We aimed to evaluate the current evidence on the benefits of NAC supplementation on physical performance and laboratory biomarkers in adult men. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically reviewed studies indexed in the Web of Science, Scopus, and PubMed to assess the effects of NAC on physical performance, laboratory biomarkers, and adverse effects in adult men. Original articles published up to 30 April 2023 with a controlled trial design comparing NAC supplementation with a control group were included. The modified McMaster Critical Review Form for Quantitative Studies was used as an assessment tool and the Cochrane Risk of Bias was applied. Of the 777 records identified in the search, 16 studies met the inclusion and exclusion criteria. Overall, most of the trials reported beneficial effects of NAC supplementation and no serious adverse events were reported. Participants supplemented with NAC showed significant improvements in exercise performance, antioxidant capacity, and glutathione homeostasis. However, there was no clear evidence of beneficial effects of NAC supplementation on haematological markers, inflammatory response, and muscle behaviour. NAC supplementation appears to be safe and may regulate glutathione homeostasis, have antioxidant effects, and improve exercise performance. However, further studies are needed to clarify the relevance of its use.

6-Week Supplementation with Tribulus terrestris L. to Trained Male CrossFit® Athletes on Muscle, Inflammation, and Antioxidant Biomarkers: A Randomized, Single-Blind, Placebo-Controlled Trial.

Tribulus terrestris L. (TT) ingredients have anti-inflammatory and antioxidant activities, but their effects on exercise-induced muscle damage (EIMD) in trained athletes are uncertain. The purpose of this single-blind placebo-controlled trial, in accordance with CONSORT guidelines, was to examine the effect of 6 weeks of TT supplementation on muscle metabolism, inflammation biomarkers, and oxidant status. Thirty trained male CrossFit® athletes were randomly assigned to be supplemented with 770 mg/day of TT (intervention group (IG)) or receive a placebo daily (control group (CG)) for 6 weeks. Muscle damage enzymes, inflammation biomarkers, and Total Antioxidant Status (TAS) were assessed at baseline (T1), 21 days after baseline (T2), and after 42 days (T3). Grace, a Workout of the Day, was measured in T1 and T3. Statistical significance (p < 0.05) was found between IG and CG in Lactate Dehydrogenase (LDH), C-reactive protein (CRP), and TAS levels at the end of the follow-up. Furthermore, TAS levels were significantly (p < 0.05) lower at T2 and T3 relative to baseline in the IG, also LDH and CRP increased significantly (p < 0.05) at T2 and T3 relative to baseline in the CG. No significant (p > 0.05) decreases in muscle damage or inflammation biomarkers were observed, although a slight downward trend was observed after 6 weeks for supplemented athletes. TT supplementation could attenuate the CrossFit® training program-induced oxidative stress, muscle damage, and inflammation which could be due to the natural antioxidant and anti-inflammatory properties of TT.