Quercetin supplementation promotes recovery after exercise-induced muscle damage: a systematic review and meta-analysis of randomized controlled trials.

None

• Quercetin at 1000mg per day for up to 6 weeks may support exercise recovery by reducing EIMD, oxidative stress and muscle soreness.

Introduction

Quercetin (Q) is a flavonoid found in apples, onions, berries, tomatoes, red grapes, leafy greens and tea. Due to its antioxidant capacity, quercetin has demonstrated antioxidative, anti-inflammatory, anti-mutagenic, and anti-carcinogenic properties.

Intense physical exercise may lead to an increase in reactive oxygen species, oxidative stress and exercise induced muscle damage (EIMD). This systematic review and meta-analysis aimed to determine the effect of Q supplementation on EIMD including muscle soreness, inflammation, antioxidant capacity and oxidative stress after intense exercise.

Methods

• This systematic review and meta-analysis was designed according to PRISMA guidelines.
• The studies were assessed using the Cochrane Collaboration risk of bias tool.
• 13 studies were included: 12 of the studies were randomised placebo-controlled trials; 6 of the studies had a parallel group design; 7 of the studies had a cross-over design.
• There were a total of 249 participants.
• 12 of the studies used a dose 1000 mg of Q per day.
• Supplementation duration ranged from a single dose 3h prior to exercise to 6 weeks of daily supplementation.

Results

• Q led to a significant reduction in perceived muscle soreness 0/24 h post exercise (SMD: -1.33; 95% CI: [-2.57, -0.09]; p = 0.03).
• Q resulted in a significant reduction in creatine kinase levels 24/48 h post exercise (SMD: -1.15; 95% CI: [-2.09, -0.21]; p = 0.02).
• Q resulted in reduced oxidative stress following exercise (SMD: -0.92; 95% CI: [-1.73, 0.11]; p = 0.03).
• Q supplementation did not significantly impact antioxidant activity following exercise, despite a trend towards significance (SMD: 0.26; 95% CI: [-0.02, 0.54]; p = 0.06).
• There were no significant between-group differences in IL-6 concentrations post-exercise (SMD: -0.09; 95% CI: [-0.42, 0.23]; p = 0.58).

Conclusion

This meta-analysis highlighted the potential for Q to support muscle recovery, reduce muscle damage and soreness and reduce oxidative stress following exercise.

• Supplementing with 1000mg of quercetin per day for up to 6 weeks may support exercise recovery by reducing muscle soreness, muscle damage and oxidative stress in both sedentary and well trained healthy young men.

• The exercise protocol to induce muscle damage varied across the studies resulting in different levels of muscle damage. Further studies utilising a uniform protocol to induce muscle damage may help to determine quercetin’s effect on exercise recovery. Also assessment of histamine release and impact on muscle soreness/damage markers would be beneficial.
• Most of the studies included healthy young male participants. Further studies including female, highly trained athletes and older subjects would be useful to determine the effects of quercetin supplementation on exercise recovery in those populations.
• The study durations were up to 6 weeks. Longer studies are needed to identify the long-term benefits of quercetin supplementation for exercise recovery or potential risks.
• Further studies controlling for diet and dietary polyphenols may identify a potential synergistic relationship between Q and other polyphenols and reduce study bias.