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

Abstract

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 (0.7g/kg of body mass), and (iii) after 4 weeks of daily supplement consumption (0.3g/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 15-20s contraction of the vastus lateralis. Cranberry supplementation over 28 days significantly improved muscle oxidative capacity (k-constant, 2.8±1.8vs. 3.9±2.2; p=0.02). This was supported by a greater rate of oxygen depletion during a sustained cuff occlusion (-0.04±0.02vs. -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.