An interventional study of New Zealand Blackcurrant Extract (CurraNZ®) and Placebo (Maltodextrin) in Exercise-induced Muscle Damage, Oxidative Stress and Inflammation, sponsored by Hacettepe University. Completed at 1 site in Turkey (Türkiye). Open to male participants aged 18 Years to 35 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-18.
Sponsored by Hacettepe University · Not applicable, Interventional, and Supportive care
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.
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Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
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Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants received New Zealand blackcurrant extract capsules (CurraNZ®, Healthspan Elite, UK) for 7 days. The daily dose was 600 mg (two 300 mg capsules, morning and evening), providing approximately 210 mg anthocyanins per day.
Dietary Supplement: New Zealand Blackcurrant Extract (CurraNZ®)
Participants received placebo capsules identical in appearance to the NZBC capsules, containing maltodextrin. The placebo was administered orally twice daily for 7 days.
Dietary Supplement: Placebo (Maltodextrin)
Standardized anthocyanin-rich blackcurrant extract administered orally at 600 mg/day (two 300 mg capsules) for 7 consecutive days. Each capsule contained natural polyphenolic compounds standardized to \~35% anthocyanins.
Two identical capsules containing maltodextrin, taken daily for 7 days (morning and evening), matching the NZBC supplementation schedule.
Change in plasma Creatine Kinase (CK) concentration
Plasma creatine kinase (CK) activity measured via ELISA assay as a biomarker of exercise-induced muscle damage. The outcome represents the change in CK levels from baseline to 24 h and 7 d after repeated high-intensity training sessions.
Time frame: Baseline, immediately post-exercise, 24 hours, and 7 days after training
Change in Reactive Oxygen Species (ROS) levels
ROS concentrations measured by ELISA to assess oxidative stress response following high-intensity training.
Time frame: Baseline, immediately post-exercise, 24 hours, and 7 days
Change in Total Antioxidant Capacity (TOAC)
Total antioxidant capacity determined spectrophotometrically using commercial assay kits (Sunredbio, China). Reflects systemic antioxidant defense.
Time frame: Baseline, 24 hours, and 7 days
Change in Inflammatory Cytokines (IL-6, TNF-α, IL-10)
Serum IL-6, TNF-α, and IL-10 quantified by ELISA to evaluate systemic inflammatory and anti-inflammatory responses to exercise and supplementation.
Time frame: Baseline, 24 hours, and 7 days
Perceived Muscle Soreness (Visual Analog Scale, VAS)
Subjective muscle soreness assessed using a 10-cm visual analog scale (VAS), where 0 = no soreness and 10 = extreme soreness.
Time frame: Baseline, 12 hours, 24 hours after each training day, and 7 days
Plan to share: Yes — Individual participant data (IPD) that underlie the results reported in this article (deidentified participant data, including baseline characteristics and outcome measures) will be made available upon reasonable request to qualified researchers. Data will be available after publication of the main results for a period of 3 years. Requests should be directed to the corresponding author (Assoc. Prof. Sedat Arslan, Bandirma Onyedi Eylul University; email: sarslan@bandirma.edu.tr). No identifying participant information will be shared. Supporting documents such as the study protocol, statistical analysis plan, and informed consent form will also be provided upon request.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Analytic code
Time frame: Deidentified IPD and supporting documents will be available beginning 1 month after publication of the primary results and for 36 months thereafter. If publication is delayed, access will begin 12 months after database lock. Extensions may be granted upon justified request.
Access criteria: Qualified researchers with a methodologically sound proposal may request access by emailing the corresponding author (Assoc. Prof. Sedat Arslan; sarslan@bandirma.edu.tr). Requests must include a brief protocol, objectives, analysis plan, and IRB/ethics determination (if applicable). A data use agreement is required. Only deidentified IPD (baseline characteristics and prespecified outcomes) and documentation (protocol, SAP, ICF templates, analytic code) will be shared. Data will be provided via a secure institutional repository link; re-identification and commercial use are prohibited.
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