Okara Supplementation Relieves Fatigue and Muscle Damage that Occur during Exercise Training

Abstract

Okara, the soybean residue from soy milk production, contains nutrients and functional components. The objective of this study was to investigate the effect of okara supplementation on fatigue and muscle damage in university athletes over an exercise training season. A total of 23 male university baseball players aged 18-23 years attending a summer intensive exercise training program completed an 8-week exercise training-okara intervention study. The supervised exercise training program consisted of physical and technical training including warm-up exercises, physical and skill practice, and pre-game competition practice. Okara supplementation in this study was a randomized, double-blind and crossover dietary intervention in which subjects consumed 2 cookies/day containing of soybean or black soybean okara for a period of 6 weeks with a one-week washout period. Blood was drawn 4 times within an 8-week intervention period for measurements of biomarkers for fatigue and muscle damage. The results demonstrated significant differences in blood levels of ammonia, free fatty acids, creatine kinase, myoglobin, and aspartate transferase between baseline and exercise training, indicating that fatigue and muscle damage occurred during exercise training. However, those increased markers of fatigue and muscle damage were significantly decreased after the okara supplementation regardless of whether soybean okara or black soybean okara cookies were consumed. This is the first study to demonstrate that okara supplementation is beneficial to university baseball players who experience exercise training-related fatigue and muscle damage. Fatigue and muscle damage occurring during exercise training were both relieved, indicating that okara cookies are feasible sports nutrition supplements.