New Zealand Blackcurrant and Recovery in Elite Taekwondo

Overview

This randomized, double-blind, placebo-controlled trial evaluated the effects of short-term supplementation with anthocyanin-rich New Zealand blackcurrant (NZBC) extract on exercise-induced muscle damage, oxidative stress, antioxidant status, inflammatory responses, and perceived muscle soreness in elite male taekwondo athletes. Thirty national-level male taekwondo athletes were enrolled and randomly assigned in a 1:1 ratio to receive either NZBC extract (CurraNZ®, UK; 600 mg/day providing approximately 210 mg anthocyanins) or a matched placebo for 7 days. Blood samples and muscle soreness ratings were collected at baseline, immediately after exercise, 24 hours after exercise, and after 7 days. The primary outcome was plasma creatine kinase (CK). Secondary outcomes included reactive oxygen species (ROS), total antioxidant capacity (TOAC), protein carbonyls, inflammatory cytokines (IL-6, TNF-α, and IL-10), and perceived muscle soreness assessed using a visual analog scale (VAS). The study was approved by the Biruni University Clinical Research Ethics Committee (No. 2015-KAEK-80-23-33; December 22, 2023). Written informed consent was obtained from all participants.

High-intensity, impact-based sports such as taekwondo involve substantial mechanical and metabolic demands that may contribute to exercise-induced muscle damage, oxidative stress, inflammatory responses, and delayed recovery. Nutritional strategies capable of modulating these physiological responses may therefore be relevant for athletes exposed to repeated high-intensity training. New Zealand blackcurrant (Ribes nigrum L.) is rich in anthocyanins and other polyphenolic compounds with antioxidant and anti-inflammatory properties. Previous studies involving endurance and intermittent exercise have investigated the potential effects of blackcurrant supplementation on oxidative stress, vascular responses, exercise performance, and recovery. However, evidence in elite combat-sport athletes remains limited. The objective of this randomized controlled trial was to determine whether 7 days of standardized NZBC extract supplementation influenced biochemical markers of muscle damage, oxidative stress, antioxidant status, inflammatory cytokines, and perceived muscle soreness following repeated high-intensity training in elite male taekwondo athletes. It was hypothesized that NZBC supplementation would attenuate exercise-associated elevations in plasma creatine kinase and reactive oxygen species, increase total antioxidant capacity, and modulate inflammatory cytokine responses, including IL-6, TNF-α, and IL-10. The study used a randomized, double-blind, placebo-controlled, parallel-group design and was conducted at the Atik Ali Sports Club in Istanbul, Türkiye, between December 2023 and June 2024. Thirty elite male taekwondo athletes were enrolled and randomly allocated in a 1:1 ratio to receive either NZBC extract or placebo. Participants assigned to the intervention group received 600 mg/day of New Zealand blackcurrant extract (CurraNZ®, UK), providing approximately 210 mg of anthocyanins, for 7 consecutive days. Participants assigned to the control group received a visually matched maltodextrin placebo. Randomization, allocation concealment, and blinding procedures were maintained throughout the intervention and until database lock. Blood samples were collected at baseline, immediately following exercise, 24 hours after exercise, and after 7 days. Biochemical outcomes included plasma creatine kinase, reactive oxygen species, total antioxidant capacity, protein carbonyls, IL-6, IL-10, and TNF-α. Biomarkers were assessed using commercially available laboratory assay kits. Perceived muscle soreness was evaluated using a visual analog scale. Dietary intake and anthropometric characteristics were also assessed. The primary outcome was the change in plasma creatine kinase. Secondary outcomes included reactive oxygen species, total antioxidant capacity, protein carbonyls, IL-6, IL-10, TNF-α, and perceived muscle soreness. Statistical analyses were conducted using R version 4.3.1. Data distribution was assessed using the Shapiro-Wilk test, and homogeneity of variance was evaluated using Levene's test. Between-group comparisons were planned using independent-samples t-tests or Mann-Whitney U tests, as appropriate. Longitudinal changes were evaluated using repeated-measures analysis of variance, including group, time, and group × time interaction effects. Greenhouse-Geisser corrections were applied where assumptions of sphericity were not met. Sensitivity analyses were conducted using linear mixed-effects models. Statistical significance was defined as a two-tailed alpha level of 0.05. The study was approved by the Biruni University Clinical Research Ethics Committee (No. 2015-KAEK-80-23-33; December 22, 2023). All participants provided written informed consent before participation.