A major new paper has just been published and it's an exciting moment for CurraNZ.
A systematic review and meta-analysis¹ in the Journal of Dietary Supplements has pooled all the human exercise studies using our clinically researched New Zealand blackcurrant extract. The paper explores how CurraNZ supplementation was associated with changes in the way participants used fat and carbohydrate as fuel sources during exercise across 15 controlled trials.
Why This Paper Matters: Top-Tier Evidence
In nutrition science, not all evidence carries the same weight. This new publication by Cook, Bateman and Willems is a systematic review and meta-analysis, which sits at the top of the evidence hierarchy.
A systematic review uses a comprehensive search strategy to find and screen eligible studies on a topic, minimising bias and selecting appropriate studies.
A meta-analysis then statistically combines the data from those trials to calculate an overall effect, giving the clearest picture yet of how reliable and meaningful the results are.
Crucially, every single study included used CurraNZ – the global science leader in blackcurrant products and the only brand globally supported by a comprehensive dossier of research. The conclusions in this meta-analysis speak directly to our product and the exercise metabolism findings observed in the research.
How the Research Was Done
The authors searched major scientific databases (PubMed, Web of Science, SPORTDiscus) between May and November 2025, working from a preregistered protocol (CRD420251030222) and following recognised reporting guidelines.
To make the cut, studies had to:
• Test blackcurrant supplementation in healthy, physically active adults aged 18–65
• Measure absolute rates of fat and carbohydrate oxidation during exercise (in grams per minute)
• Include a placebo or control condition for comparison
What the researchers found:
• 15 studies, 226 participants (192 men, 34 women)
• All used New Zealand blackcurrant extract CurraNZ™, with the final dose taken 2 hours before the exercise test
• Exercise modes: 6 cycling studies, 9 treadmill walking/running studies
• Dosing: Most used 210 mg/day anthocyanins for 7 days, with some studies testing 105–315 mg/day and intake from a single acute dose up to 14 days
The team used a random-effects meta-analysis, which accounts for differences between study designs and populations, to calculate the overall association between CurraNZ supplementation and changes in fat and carbohydrate use during exercise.
The Headline Results: What the Research Observed
When all the studies were combined, the pooled data showed a statistically significant shift in exercise fuel use in participants who took CurraNZ compared to placebo.
Fat Oxidation
• Average increase in fat oxidation in the CurraNZ group: +0.042 g·min⁻¹. Over a 2-hour steady-state session, this average effect equates to roughly an extra ~5 grams of fat oxidised, consistent with individual trials showing higher total fat use across 120 minutes of cycling at moderate intensity.
Carbohydrate Oxidation
• Average reduction in carbohydrate oxidation in the CurraNZ group: −0.099 g·min⁻¹. The size of this effect varied more between studies, but the overall direction remained consistent.
Individual Responses Vary
The meta-analysis also highlights what is commonly observed across the individual trials: responses differ between people.
Of the 15 studies, 8 showed statistically significant changes in substrate oxidation; 7 reported no meaningful group-level effect, even though the pooled result was positive.
Other work cited in the paper notes that in women, the magnitude of the fat-oxidation shift appeared to correlate with body fat percentage. Additionally, individuals who were more carbohydrate-dependent at baseline (higher respiratory exchange ratio, or RER, under placebo) appeared to show larger shifts when supplementing with CurraNZ.
The research suggests the profile of participants most likely to show a notable shift includes active individuals who naturally rely more heavily on carbohydrates during steady aerobic exercise.
What the Research Involved: Active Adults and Exercise
For runners, cyclists, gym-goers and recreational exercisers, this meta-analysis offers the strongest and most comprehensive body of evidence to date exploring how CurraNZ supplementation may be associated with metabolic flexibility during exercise – the body’s ability to shift between fuel sources.
Contextual notes from the research:
• Higher fat oxidation during exercise has long been of interest to endurance athletes and researchers as it relates to fuel use and carbohydrate sparing.
• Independent research cited in the paper observed that training at intensities that maximise fat oxidation was associated with changes in body composition over a 10-week period.
How CurraNZ Was Used in the Studies
The research protocols provide useful context on how CurraNZ was taken across the included studies:
• Dose: Typically 210 mg/day of blackcurrant anthocyanins
• Duration: 7 days of daily intake, with some studies extending to 14 days or exploring 105–315 mg/day
• Timing: Last dose taken 2 hours before the key exercise bout
• Exercise: 30–120 minutes of walking, running or cycling at moderate intensity (often 50–65% VO₂max or at lactate threshold)
An Honest Look at the Limitations
The authors are careful not to over-interpret the data:
• All included studies used the same standardised CurraNZ extract. These findings cannot be assumed to apply to generic blackcurrant or berry products, juices, or non-standardised powders with different anthocyanin profiles.
• Participants were healthy, physically active adults; more data is needed in sedentary individuals, older adults and clinical populations – although separate work has shown changes in resting fat oxidation after 14 days of CurraNZ in healthy men.
• This meta-analysis focuses on substrate use during exercise, not performance outcomes. Other CurraNZ trials and case studies are encouraging, but direct performance outcomes were not the primary focus here.
• Some methodological details (such as randomisation procedures and preregistered analysis plans) were not consistently reported across all trials, even though the core measurements (gas exchange, oxidation rates) are objective.
The Take-Home
This new meta-analysis marks a significant milestone in the CurraNZ story. Across 15 controlled trials in active adults, supplementation with our New Zealand blackcurrant extract was consistently associated with a shift in exercise metabolism towards greater fat use and lower carbohydrate use – with results robust enough to withstand the highest level of scientific scrutiny.
Used alongside smart training, good nutrition and proper recovery, CurraNZ now has a stronger body of research than ever supporting its use as part of an active lifestyle.
Be aware of imitation and adulterated products – only products that bear the Enza’s quality mark can be assured of delivering the standardised extract used in the research.
* CurraNZ is a food and is not intended to diagnose, treat, cure or prevent any disease or health condition. The research referenced describes findings observed in the context of specific controlled exercise studies. Individual results may vary.
Reference
¹ Cook, M. D., Bateman, J. J., & Willems, M. E. T. (2026). Blackcurrant Anthocyanin Supplementation Alters Exercise-Induced Substrate Utilization – A Systematic Review and Meta-Analysis. Journal of Dietary Supplements, 1–16. https://doi.org/10.1080/19390211.2026.2624114