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Blackcurrant (Ribes nigrum)
An anthocyanin-rich berry (Ribes nigrum) studied mainly for eye function and exercise blood flow. Small RCTs suggest it eases visual fatigue and increases ocular blood flow, and improves cycling performance/fat oxidation — but trials are small, single-product (CurraNZ), and some recovery endpoints came back null.
What the evidence says
Most Blackcurrant studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from high-quality meta-analyses and randomised trials published 2000–2026 with a typical study size of 15 participants.
Based on 63 studies · 2 meta-analyses · 58 RCTs · 1,005 total participants
Confidence
High confidenceBy outcome
Small RCTs show real signals for cycling performance and ocular blood flow/visual fatigue, but the whole evidence base is a handful of tiny, mostly single-product (CurraNZ) trials with one null recovery endpoint.
59 rigorous studies
57 randomized trials · 2 meta-analyses · 2 systematic reviews
Our evidence rating for Blackcurrant is accountable to this entire body of rigorous research indexed in PubMed — not a hand-picked subset.
PubMed · as of Jul 2026
6 trials ongoing or recruiting · 48 completed on ClinicalTrials.gov
2 of the completed trials have posted results
Registered trials show research momentum for Blackcurrant, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Sep 2026
Under EU law (Reg. 1924/2006), EFSA reviews whether a specific health claim for Blackcurrant meets the evidence standard. These are independent regulatory decisions on claims — not studies, and never counted toward the evidence score above.
Not authorised by EFSA
“Blackcurrant Ribes nigrum Blackcurrant is rich in the antioxidants anthocyanins Blackcurrant is rich in antioxidants”
“Black Currant juice Blackcurrent juice helps to : - protect cells against oxidative damages - strengthen the immune system”
“Cassis : Dry extract of Ribes Nigrum fruit standardized at 7% of anthocyanosides Can help to reduce eyestrain. Can help to improve night vision”
“Black Currant juice Blackcurrent juice helps to: - improve the urinary tract immune function. - support the normal functionning of the urinary tract”
“Not authorised” means the specific claim wording did not meet the EU’s evidence standard — often a matter of dossier or phrasing, not proof of no effect. EFSA judges marketing claims and is kept separate from our study-based evidence score.
Source: EU Register of nutrition and health claims (European Commission / EFSA) · register snapshot Feb 2013
Blackcurrant is exceptionally rich in anthocyanins (notably delphinidin and cyanidin glycosides), which underpin two distinct evidence streams.
For vision: a double-blind crossover study found blackcurrant anthocyanosides dose-dependently lowered the dark-adaptation threshold and reduced VDT (screen)-induced visual fatigue at 50mg, and a 2-year RCT in open-angle glaucoma patients found slowed visual-field deterioration and increased ocular blood flow versus placebo (though no change in intraocular pressure).
For exercise: standardized New Zealand blackcurrant extract (CurraNZ) increased peripheral blood flow, raised fat oxidation, and improved 16.1km cycling time-trial performance by ~2.4% in trained cyclists.
The honest caveats are substantial: most trials are small (often <40 people), heavily reliant on a single commercial product, and results are not uniformly positive — a half-marathon recovery RCT found no effect on muscle-damage recovery, soreness, or fatigue.
Blackcurrant is a promising but early-stage performance/eye supplement, not an established one.
Anthocyanins increase peripheral and ocular blood flow, proposed to aid substrate delivery during exercise and perfusion in the eye.
Standardized extract raises fat oxidation during moderate-intensity exercise in trained athletes.
Anthocyanins are proposed to support rhodopsin regeneration and reduce ciliary-muscle strain, lowering dark-adaptation threshold and screen-induced visual fatigue.
How Blackcurrant works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
May be a useful adjunct alongside (not a replacement for) prescribed antiglaucoma therapy; discuss with an ophthalmologist.
Dietary amounts are fine; standardized supplemental extracts are not specifically studied — consult a clinician.
Anthocyanins may have mild effects on platelet aggregation/blood flow; generally benign but worth noting with blood thinners.
Tip: Take with food; reduce dose
Blackcurrant has an evidence score of 4/10 — emerging evidence based on 50 indexed studies. An anthocyanin-rich berry (Ribes nigrum) studied mainly for eye function and exercise blood flow. Small RCTs suggest it eases visual fatigue and increases ocular blood flow, and improves cycling performance/fat oxidation — but trials are small, single-product (CurraNZ), and some recovery endpoints came back null. Representative study: PMID 22377796.
The commonly studied dose of Blackcurrant is 300mg standardized NZ blackcurrant extract (~105mg anthocyanin) daily for exercise; ~50mg anthocyanins daily for visual outcomes. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Timing is flexible for Blackcurrant — consistent daily use matters more than the time of day. For exercise, load for ~7 days; can be taken 1-2 hours before activity.
Blackcurrant is generally well-tolerated and considered safe for most healthy adults at recommended doses. Reported side effects are uncommon and include mild GI upset. Use caution if any of these apply to you: No major contraindications at dietary/supplemental doses.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 63 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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