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 study aimed to investigate the effect of a polyphenol-rich cranberry extract (CE) on muscle oxidative capacity and oxygenation metrics in healthy active adults. 17 participants (9 males and 8 females) were tested at: (i) baseline, (ii) 2 h 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 oxidative 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 oxidative 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 oxidative capacity in healthy active adult populations.

Cranberry supplementation improves physiological markers of performance in trained runners.

PURPOSE: Cranberries have the highest polyphenol and antioxidant capacity among fruits and vegetables and may protect against exercise-induced free radical production, consequently improving performance. This study aimed to investigate the effect of polyphenol-rich cranberry extract (CE) on time-trial performance and lactate response following exercise. METHODS: A total of 14 trained runners were tested at i) baseline, ii) 2 h following an acute CE dose (0.7 g/kg of body mass), and iii) 4 weeks after daily supplement consumption (0.3 g/kg of body mass). At each time point, runners performed a 1500-m race followed by a 400-m race where the live vastus lateralis oxygenation changes were determined by near-infrared spectroscopy and blood lactate was measured at rest and 1 and 3 min after each trial. The Shapiro-Wilk test and repeated-measures analysis of variance were used to establish significance (P <0.05). RESULTS: Cranberry supplementation over 28 d improved aerobic performance during the 1500-m time trial, whereas the acute dose had no effect. More specifically, muscle reoxygenation rates were significantly faster after 28 d compared to baseline (P = 0.04; η² = 0.29), and a trend towards slower deoxygenation rate was observed (P = 0.13; η² = 0.20). Chronic CE consumption also buffered the post-exercise lactate response for the 400-m race (P = 0.01; η² = 0.27), while no effects were seen for the longer race. CONCLUSION: Our results suggest that cranberry supplementation may have ergogenic effects, as it improves physiological markers of performance during short- and long-distance running.