A polyphenol-rich cranberry supplement improves muscle oxidative capacity in healthy adults.

Cranberries are rich in polyphenols, have a high antioxidant capacity, and may protect against exercise-induced free radical production. Mitochondria are known producers of free radical in skeletal muscle, and preventing overproduction of radicals may be a viable approach to improve muscle health. This stud aimed to investigate the effect of a polyphenol-rich cranberry extract on muscle oxidative capacity and oxygenation metrics in healthy active adults. 17 participants (9 males, 8 females) were tested at: i) baseline, ii) 2 hours following an acute CE dose (0.7 g/kg of body mass), and iii) after 4 weeks of daily supplement consumption (0.3 g/kg of body mass). At each time point, muscle oxygen capacity was determined using near-infrared spectroscopy to measure the recovery kinetics of muscle oxygen consumption following a 15-20 s contraction of the vastus lateralis. Cranberry supplementation over 28 days significantly improved muscle oxygen capacity (k-constant, 2.8 ± 1.8 vs. 3.9 ± 2.2; p = 0.02). This was supported by a greater rate of oxygen depletion during a sustained cuff occlusion (-0.04 ± 0.02 vs. -0.07 ± 0.03; p = 0.02). Resting muscle oxygen consumption was not affected by cranberry consumption. Our results suggest that cranberry supplementation may play a role in improving mitochondrial health, which could lead to better muscle oxygen capacity in healthy active adult populations. The study protocol was registered with ClinicalTrials.gov (#NCT06186297).