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Study under review: Flavonoid Containing Polyphenol Consumption and Recovery from Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis
Exercise, especially when it involves high-force eccentric or unaccustomed loading, can produce substantial muscle fiber damage. It is thought that the initial structural damage from mechanical loading causes uncontrolled movement of calcium ions into the cytoplasm, leading to further degradation of structural proteins. While the inflammatory response that follows is aimed at clearing damaged tissue, it may result in an excessive production of reactive oxygen species, which further damage the muscle fibers. Eventually, this exercise-induced muscle damage (EIMD) manifests as muscle pain and swelling, strength and power loss, reduced range of motion (ROM), and delayed onset muscle soreness (DOMS), with these symptoms usually subsiding five to seven days after exercise.
Some research suggests that flavonoids, a class of polyphenols found in high concentrations in fruits, vegetables, and other plants, may promote exercise recovery and protect against EIMD thanks to their antioxidative and anti-inflammatory properties. For example, a 2019 meta-analysis found that the consumption of whole fruits high in anthocyanins (a type of flavonoid) improved exercise-induced inflammation and oxidative stress in healthy adults. Moreover, a 2019 narrative review of randomized controlled trials suggested that supplementation with more than 1,000 mg of polyphenols for three days before and after exercise may enhance recovery from EIMD. However, a meta-analysis quantitatively analyzing the results of the available randomized controlled trials specifically looking at the effects of flavonoid polyphenols on markers of EIMD is lacking.
Other Articles in Issue #79 (May 2021)
Mini: Sports nutrition tips for active women
We provide some of the big-picture takeaways from a recent narrative review covering nutritional strategies for active women.
Nulls: January-February 2021
Get a quick rundown of recent studies that found no evidence for an effect in the latest installment of Nulls!
A modified keto diet may slow some declines associated with Alzheimer’s disease
This recent trial found that a keto diet helped people with mild Alzheimer's disease perform activities of daily living while improving their quality of life.
Deeper Dive: Cinnamon may improve biomarkers of metabolic diseases
This meta-analysis found cinnamon supplementation can improve lipid levels, blood pressure, glycemic control, and waist circumference in adults with metabolic diseases. While these results are promising, there are still quite a few open questions.
Deeper Dive: A spoonful of vinegar might make blood sugar go down
Acetic acid may help with glycemic control while lowering triglycerides, but the studies included in this meta-analysis had a high risk of bias.
Investigating the efficacy of protein supplementation for older people with and without resistance training
This randomized controlled trial found that protein supplementation needs to be paired with heavier resistance training to help keep older people's muscles healthy.
Betaine supplementation: a double-edged sword for CVD markers
This meta-analysis suggested that betaine doses under 4 grams daily can lower homocysteine without necessarily raising LDL-C, but there's still a lot of uncertainty.