The Guest Author Spotlight is back with Korey Van Wyk, a nutrition and exercise education professional, who brings us a systematic review examining the effects of N-acetylcysteine on physical performance and biomarkers.
Researchers analyzed 16 controlled trials that tested NAC in adult men who were healthy, physically active, or competitive athletes.
In most studies, NAC was provided orally at 1,200 mg/day, split into two 600 mg doses for about a week. The trials assessed everything from performance measures (time to exhaustion, total work, VO₂max, power) to biomarkers (glutathione levels, total antioxidant capacity, lipid peroxidation, inflammatory cytokines) and side effects.
Key findings:
Supplementation consistently raised glutathione and improved total antioxidant capacity.
Concerning performance, NAC supplementation was found to improve:
Time to exhaustion
Peak cycling power
Average power in shorts sprints (5, 10, and 15 seconds)
Soreness scores
Perhaps most importantly, researchers noted NAC's safety profile, with minimal mild adverse reactions.
When you train hard, your muscles generate a flood of reactive oxygen species (ROS), unstable molecules that, in excess, can impair recovery. One of your body’s main defenses against this is glutathione, a powerful antioxidant inside cells.
NAC provides cysteine, the raw ingredient your body needs to replenish glutathione. With higher glutathione, your muscles can neutralize oxidative stress more effectively, which means less damage and faster recovery.
NAC may also help preserve the function of ion pumps in muscle cells that control sodium, potassium, and calcium. These pumps are vital for repeated contractions. When they falter, fatigue sets in sooner. By protecting them, NAC may delay the point of muscle failure, especially during repeated or prolonged efforts
Lastly, NAC helps regulate inflammatory pathways (like NF-κB). Importantly, the result is not a complete shutdown of inflammation but rather a dampening of excessive signals, creating a better environment for repair without blunting adaptive signals from training.
Korey’s Application
NAC has been a popular go-to supplement for athletes, especially when it comes to recovery. This review further solidifies its place among other ingredients in high-performance health.
For the health-conscious athlete, NAC is a strategic recovery tool, best deployed when oxidative stress or muscle damage is likely to be high.
Vitality Recommendation: Supplement with at least 600 mg of NAC daily.
Be sure to check out the latest episode of Vitality Unlocked on the YouTube Channel.
About the Author: Korey Van Wyk, MS, CSCS, Pn2 is a nutrition and exercise education professional who has held roles in higher education, publishing, and strength and conditioning. He uses his multifaceted background to convey scientific information into clear, evidence-based content that serves both professional and consumer audiences.
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