Sixteen ounces per day of the blackcurrant nectar were associated with reductions in the activity of creatine kinase, a blood marker of muscle damage, by 6.7%, compared to 82% increases in activity in the placebo group 48 hours after exercise, report the researchers in the Journal of Dietary Supplements.
Researchers led by Alexander Hutchison, PhD, also report that levels of the inflammatory compound interleukin-6 decreased after exercise in participants in the blackcurrant group, compared with increases seen in the placebo group.
“In partial support of our primary hypotheses, we found that consumption of black currant nectar for four days before and three days after a bout of eccentric leg exercise significantly reduced circulating markers of muscle damage while maintaining circulating antioxidant capacity,” they wrote in their paper. “Although pain scores in the blackcurrant nectar group returned to baseline a day earlier than the placebo group, there were no significant differences observed between groups at any time point after exercise.
“To our knowledge, this is the first study to examine the effects of consumption of blackcurrant nectar on symptoms of [exercise-induced muscle damage] in untrained, healthy participants.”
Blackcurrants are a good source of vitamin C, anthocyanins and other antioxidants, while the seeds are also rich in omega-6 GLA. According to the USDA, 100 grams of black currants provides about 181 mg of vitamin C.
Commenting on the potential mechanism of action, Dr Hutchison and his co-authors noted that the beneficial effects of the blackcurrant intervention were most likely via antioxidant activity to neutralize reactive oxygen species which could damage myofibers, and protecting against further damage to muscle cell membranes and reducing or preventing additional creatine kinase leakage.
The study included 16 college students randomly assigned to consumer either the blackcurrant nectar beverage (CurrantC provided by CropPharms from Staatsburg, NY) or placebo twice a day for eight days. On day 4 the participants performed a bout of knee extension exercises, and blood samples taken 24, 48, and 96 hours after the exercise.
Results showed that ORAC levels in the blood significantly decreased in the placebo group, while no significant decreases from the baseline values were observed in the blackcurrant group. In addition, significant differences between the groups were observed for IL-6 levels 24 hours after exercise, while significant differences were observed in creatine kinase activity between the groups after 48 and 96 hours..
“Our results suggest that the critical window during which supplementation is most effective in reducing symptoms of [exercise-induced muscle damage] is immediately after eccentric exercise,” wrote the researchers. “This is when the circulating concentration of ROS is rapidly increasing, spilling from the disrupted myofibers (along with creatine kinase).
“Although supplementation of antioxidants before exercise appears to reduce the initial flood of ROS, as evidenced by a blunted increase in creatine kinase activity at 24 h, continued supplementation with antioxidants after eccentric exercise appears to rapidly reverse [exercise-induced muscle damage] by as early as 48 h post-exercise.”
Source: Journal of Dietary Supplements
Published online ahead of print, doi:10.3109/19390211.2014.952864
“Black Currant Nectar Reduces Muscle Damage and Inflammation Following a Bout of High-Intensity Eccentric Contractions”
Authors: A.T. Hutchison, E.B. Flieller, K.J. Dillon, B.D. Leverett