Black Currant Seed Oil Benefits: What the Human Trials Actually Measured
Search for black currant seed oil benefits and you will find a confident list: skin, inflammation, immunity, joints, menopause. Search for the trials behind that list and you will find something much smaller — a handful of human studies, most of them decades old, several of which reported a result that did not hold when the researchers looked again later. This article sets out every human trial on the oil we were able to verify against the primary record, what each one measured, how large it was, and what it did not show. It is a shorter and more equivocal story than the category suggests, and that is the honest finding rather than a hedge.
For what the oil is, where it comes from and how its composition varies, see our companion article on blackcurrant seed oil and how to judge a bottle. Sidr & Stone does not sell it; we make a cold-pressed Ethiopian black seed oil from an unrelated plant.
The Short Answer
- The human evidence for black currant seed oil is thin. We could verify six human studies, five of them published between 1993 and 2010, and two of those come from the same Finnish research group.
- The most-cited study, Wu and colleagues in the American Journal of Clinical Nutrition in 1999, was a two-month randomised trial in 40 healthy people aged 65 and over. Most of its immune measures showed no significant difference from placebo.
- The rheumatoid arthritis trial by Leventhal and colleagues reported that overall clinical responses were no better in the treatment group than in the placebo group.
- The largest trial, in 313 Finnish mothers and infants, found a lower prevalence of atopic dermatitis at 12 months but no significant difference at 24 months. The authors themselves described the effect as transient.
- Pooled evidence for GLA-containing oils as a class is mixed: a Cochrane review of herbal therapy in rheumatoid arthritis rated pain relief as moderate-certainty on 82 participants across three studies, while a separate Cochrane review found oral evening primrose and borage oil ineffective for eczema across 27 studies and 1,596 participants.
- There is no authorised health claim in Great Britain or the EU for black currant seed oil or for gamma-linolenic acid.
- Several of the measures used in these trials are surrogate markers — a blood prostaglandin level, a skin induration measurement, a cytokine concentration in breast milk. None of those is a clinical outcome.
What Black Currant Seed Oil Is Sold For
The commercial case for the oil rests almost entirely on gamma-linolenic acid, an omega-6 fatty acid that the body also makes from linoleic acid. The reasoning is mechanistic: GLA is converted to dihomo-gamma-linolenic acid, which sits upstream of signalling molecules involved in inflammation. That chain of reasoning is real biochemistry, and it is the reason the oils were investigated in the first place.
What it is not is evidence of an effect in people. A plausible mechanism tells you what to test; it does not tell you what the test found. The rest of this article is about what the tests found.
Every Human Trial We Could Verify
Each entry below was checked against the primary record for authors, journal, year, volume, issue, pages and PubMed identifier. Where a study reported a null result alongside a positive one, both are given.
| Study | Design and size | What it measured | What it reported, including nulls |
|---|---|---|---|
| Wu D, Meydani M, Leka LS, et al. Am J Clin Nutr 1999;70(4):536–543. PMID 10500023 | Randomised, double-blind, placebo-controlled (soybean oil); 40 healthy adults aged 65+; 2 months | Delayed-type hypersensitivity skin response, lymphocyte proliferation, cytokines, prostaglandin E2 | Of the delayed-type hypersensitivity antigens, only the tetanus toxoid response differed significantly from placebo. Prostaglandin E2 fell relative to placebo. No significant difference for concanavalin A response, interleukin-2, interleukin-1β or membrane fluidity |
| Leventhal LJ, Boyce EG, Zurier RB. Br J Rheumatol 1994;33(9):847–852. PMID 8081671 | Randomised, double-blind, placebo-controlled; 24 weeks; adults with rheumatoid arthritis and active synovitis | Signs and symptoms of disease activity | Scores fell relative to baseline, but the authors state that overall clinical responses were no better in the treatment group than in the placebo group. Dropout was high because the regimen required 15 large capsules a day |
| Watson J, Byars ML, McGill P, Kelman AW. Br J Rheumatol 1993;32(12):1055–1058. PMID 8252313 | Non-randomised supplementation study; volunteers and rheumatoid arthritis patients; sunflower seed oil control | Monocyte cytokine and prostaglandin production; morning stiffness | Reported improvement in morning stiffness and altered stimulated monocyte output. No randomisation, no blinding described, and no effect sizes given |
| Deferne JL, Leeds AR. J Hum Hypertens 1996;10(8):531–537. PMID 8895037 | Randomised; 27 borderline-hypertensive men; 8 weeks at 6 g/day against safflower oil | Resting blood pressure and cardiovascular reactivity during a mental arithmetic task | The reported effect was on reactivity to the task, not on resting blood pressure. Blinding is not described in the record |
| Linnamaa P, Savolainen J, Koulu L, et al. Clin Exp Allergy 2010;40(8):1247–1255. PMID 20545710 | Randomised, double-blind, placebo-controlled (olive oil); 313 pregnant mothers (151 vs 162), from gestation through breastfeeding and infant supplementation to age 2 | Atopic dermatitis prevalence and severity in the infants | Prevalence at 12 months 33.0% against 47.3% (P=0.035), with lower severity scores. At 24 months the difference was not significant (P=0.18). The authors describe the effect as transient |
| Linnamaa P, Nieminen K, Koulu L, et al. Pediatr Allergy Immunol 2013;24(6):562–566. PMID 23980846 | Substudy of the above; 31 vs 30 mothers; breast milk over the first 3 months | Cytokine concentrations in breast milk | Interleukin-4 lower (P=0.044) and interferon-γ higher (P=0.014) than the olive oil group; no significant difference for interleukin-5, interleukin-10, interleukin-12 or tumour necrosis factor. A laboratory measure, not a clinical outcome |
Read as a body of work, that is six studies, one of which is not randomised, three of which predate 1997, and two of which come from a single Finnish cohort. The largest and best-designed of them found an effect that had disappeared by the second year.
What the Pooled GLA Evidence Says
Because the blackcurrant-specific literature is so small, most pooled analyses treat GLA-containing oils — evening primrose, borage and blackcurrant seed — as a single class. Two Cochrane reviews are the relevant records, and they point in different directions.
| Review | What was pooled | Effect estimate | Heterogeneity | Certainty |
|---|---|---|---|---|
| Cameron M, Gagnier JJ, Chrubasik S. Cochrane Database Syst Rev 2011;(2):CD002948. PMID 21328257 — pain in rheumatoid arthritis | GLA oils (evening primrose, borage or blackcurrant seed), 3 studies, 82 participants | Mean difference on a visual analogue scale −32.83 (95% CI −56.25 to −9.42), P=0.006 | I² = 0% | GRADE moderate |
| Cameron 2011, same review — disability | 1 study, 41 participants | Mean difference in HAQ percentage change −15.75% (95% CI −27.06 to −4.44) | Not applicable, single trial | GRADE low — the review notes the result rests on one small trial |
| Cameron 2011, same review — adverse events | 2 studies, 61 participants | Risk ratio 4.24 (95% CI 0.78 to 22.99) — not statistically significant | Not reported | GRADE moderate |
| Bamford JT, Ray S, Musekiwa A, et al. Cochrane Database Syst Rev 2013;(4):CD004416. PMID 23633319 — eczema | 27 studies, 1,596 participants; participant-rated global symptoms for evening primrose oil, 7 studies, 176 participants | Mean difference −2.22 on a 0–100 scale (95% CI −10.48 to 6.04) — crosses zero | I² = 50% | No GRADE appraisal was carried out; the authors say so explicitly |
The Cameron review's own wording is that there is moderate evidence that oils containing GLA afford some benefit in relieving symptoms for rheumatoid arthritis. That is worth stating fairly — it is a Cochrane review and it says so. It is also worth stating fairly that the estimate rests on 82 participants across three studies, that the studies were not blackcurrant-specific, and that the review's own footnotes flag unclear randomisation concealment and outcome-assessor blinding.
The Bamford review is the harder finding for the category. Across 27 studies and 1,596 participants it concluded that oral evening primrose and borage oils are not effective treatments for eczema. Blackcurrant seed oil is essentially absent from that review, so it does not test blackcurrant directly — but it is the largest and most rigorous test of the underlying GLA hypothesis that exists, and it came back negative.
Surrogate Markers Are Not Clinical Outcomes
A recurring problem in how this literature is retold is that laboratory measurements get reported as if they were outcomes people can feel. They are not the same category of thing, and the distinction is worth making explicitly.
| What was measured | What kind of measure it is | What it does not tell you |
|---|---|---|
| Prostaglandin E2 in blood cells (Wu 1999) | A biochemical signalling marker | Whether anything the person experiences changed |
| Delayed-type hypersensitivity skin induration (Wu 1999) | A laboratory-elicited immune response | Whether the person got fewer or milder infections |
| Breast-milk interleukin-4 and interferon-γ (Linnamaa 2013) | Cytokine concentrations in a fluid | Whether any infant outcome differed |
| Blood-pressure reactivity to mental arithmetic (Deferne 1996) | A short-term physiological response to a stressor | Whether resting blood pressure or cardiovascular risk changed |
| SCORAD score at 12 months (Linnamaa 2010) | A clinical severity index — this one is a clinical outcome | Whether the difference persists; at 24 months it did not |
Only the last row describes something a parent would notice, and that is also the row where the finding did not last. Everything above it is a step in a mechanism, measured in a laboratory.
The Regulatory Position in Great Britain
The list of health claims that may lawfully be made on food in Great Britain derives from Commission Regulation (EU) No 432/2012, published in the UK on legislation.gov.uk and maintained in the Great Britain Nutrition and Health Claims Register by the Department of Health and Social Care. Only claims on that register may be used.
Gamma-linolenic acid does not appear in the Annex to that Regulation. Neither does blackcurrant, in any form. The only entry for a substance with a similar name is alpha-linolenic acid — an omega-3, chemically distinct from GLA — which carries an authorised claim relating to the maintenance of normal blood cholesterol levels, conditional on the food qualifying as a source of omega-3 fatty acids and on informing the consumer that the effect is obtained with a daily intake of 2 g of ALA.
That has a practical consequence for readers. If a UK page tells you that black currant seed oil does something specific to a condition, it is making a claim that is not on the authorised list, whatever the biochemistry behind it.
Safety, Interactions and What the Literature Does Not Say
The honest position here requires care, because the safety discussion around GLA oils is largely borrowed from a different plant. Concerns about bleeding risk, anticoagulant interaction and — historically — seizure threshold attach in the literature to evening primrose oil and, in one case report, to borage oil. The Cochrane eczema review notes that the seizure concern for evening primrose oil has been shown to be incorrect, and that animal work and drug formularies raise antiplatelet and anticoagulant interaction as a caution for it.
We found no citation raising a bleeding, anticoagulant or seizure concern specifically for blackcurrant seed oil. That is not the same as saying it has been shown to be safe in those respects; it means the question has not been asked in the published record we could find. Absence of evidence is exactly that.
The sensible course is unglamorous. If you take an anticoagulant or antiplatelet medicine, are pregnant or breastfeeding, or are managing any condition, ask a GP or a pharmacist before adding any seed-oil supplement. They can check it against what you are already taking, which no article can. The same reasoning applies to our own product, and we set it out in our piece on black seed oil and drug interactions.
Three Objections Worth Taking Seriously
"A Cochrane review said moderate evidence of benefit. Why are you being negative?"
It did, and we have quoted it. The qualification is not scepticism about Cochrane — it is what the review itself reports: 82 participants, three studies, GLA oils as a class rather than blackcurrant specifically, and downgrade footnotes on randomisation concealment and blinding. Moderate certainty on a small pooled estimate is a real signal and a fragile one at the same time.
"Old studies aren't wrong just because they're old."
Quite right, and age is not the criticism. The criticism is that the field stopped. Half of these human studies were published in the 1990s, no independent group has run a blackcurrant seed oil trial since the Finnish cohort, and a hypothesis that generates commercial interest but no new trials in more than a decade is usually telling you something.
"So is there any point taking it?"
That is a decision for you and, if a health condition is involved, for a clinician. What we can say is what the evidence supports and what it does not. It supports describing the oil as an unusual source of gamma-linolenic acid that also carries omega-3 fatty acids. It does not currently support telling anyone what it will do for them.
Why Sidr & Stone
We have no product in this category and nothing to gain from your conclusion about it. What we do have is a standing position on how supplement evidence should be described, and this article is an application of it rather than an exception to it.
- Every study named here was verified against the primary record for authors, journal, year, volume, issue, pages and PubMed identifier before publication
- Null results are reported alongside positive ones, in the same sentence where possible
- Surrogate markers are labelled as surrogate markers, not presented as outcomes
- Where a pooled estimate exists, its confidence interval, heterogeneity and certainty rating are given
- Our own product carries an independently verified per-batch thymoquinone figure, tested by Analytice, an ISO-accredited French laboratory, published with a Certificate of Analysis
- We do not make disease claims for it, and we would not want anyone else making them for us
We will not tell you our black seed oil is the strongest or the best — that is the register this whole article is arguing against. What we will say is that when a supplement is sold on a compound, the compound should be measured, and when it is sold on an outcome, the outcome should have been tested. Our guide to choosing a quality black seed oil sets out how to apply the first half of that to any bottle.
Frequently Asked Questions
What are the claimed benefits of black currant seed oil?
Sellers most often claim effects on skin, inflammation, joints, immune function and menopausal symptoms, all reasoning from the oil's gamma-linolenic acid content. The verified human trial evidence behind those claims is limited to six studies, most of them decades old, with mixed and often null results.
Is there good evidence black currant seed oil helps skin conditions?
The strongest relevant trial, in 313 Finnish mothers and infants, found a lower prevalence of atopic dermatitis at 12 months but no significant difference at 24 months, and the authors described the effect as transient. The largest test of the wider GLA hypothesis, a Cochrane review of 27 studies and 1,596 participants, found oral evening primrose and borage oil ineffective for eczema.
What did the immune study in older adults actually find?
Wu and colleagues randomised 40 healthy adults aged 65 and over to black currant seed oil or soybean oil for two months. Of the antigens tested, only the tetanus toxoid skin response differed significantly from placebo, and there was no significant difference for concanavalin A response, interleukin-2, interleukin-1β or membrane fluidity.
Is black currant seed oil good for joints?
A 24-week randomised trial in rheumatoid arthritis by Leventhal and colleagues reported that overall clinical responses were no better in the treatment group than in the placebo group. A Cochrane review pooling GLA oils as a class rated pain relief in rheumatoid arthritis as moderate certainty on 82 participants across three studies. Anyone managing a joint condition should discuss it with a GP or rheumatology team rather than self-treating.
Are there authorised health claims for GLA in the UK?
No. Gamma-linolenic acid does not appear in the Annex to Commission Regulation (EU) No 432/2012, which forms the basis of the Great Britain Nutrition and Health Claims Register maintained by the Department of Health and Social Care. Neither does blackcurrant.
Are there any safety concerns or interactions?
The bleeding, anticoagulant and seizure cautions discussed in the literature attach to evening primrose and borage oil rather than to blackcurrant seed oil, and we found no published citation raising them specifically for blackcurrant. That is an absence of evidence rather than a clean bill of health. If you take any medicine, particularly an anticoagulant or antiplatelet, ask a pharmacist or GP first.
Should I take black currant seed oil or evening primrose oil?
Neither has a strong human evidence base for a specific outcome. On composition, blackcurrant seed oil generally carries more gamma-linolenic acid than evening primrose and is the only common GLA oil that also supplies omega-3 fatty acids. On evidence, the comparison is between two thin literatures.
Is black seed oil a medicine?
No. Black seed oil is a food supplement, not a medicine. It has a long traditional history and an interesting body of research around thymoquinone, and can be a worthwhile part of a healthy routine — but it does not cure diseases and is not a substitute for medical care. Be cautious of any black seed oil marketed with specific disease-cure claims.
Final Thoughts
The most useful thing anyone can tell you about black currant seed oil benefits is how little has actually been tested. Six human studies, half of them from the 1990s, one of them not randomised, and the biggest and best of them reporting an effect that had gone by the second year. That is not a scandal; it is simply a small literature that stopped growing.
What it means practically is that the confident lists are running well ahead of the record. The composition of the oil is genuinely well characterised — that part is solid, and we have set it out in the companion article on what blackcurrant seed oil is. The clinical case for it is not, and no amount of mechanism fills that gap. Anyone with a health concern is better served by a GP or a pharmacist than by a supplement page, including this one.
Our own cold-pressed Ethiopian black seed oil is a different plant, tested per batch by a named laboratory, and available now with fulfilment in the UK, EU, and US.
Shop Sidr & Stone Cold-Pressed Ethiopian Black Seed Oil — Verified 2.67% Thymoquinone →
Disclaimer: This article describes published research findings and the regulatory position on black currant seed oil at the time of writing; research and claims registers may change, and readers should check current sources. Nothing here is a claim that any product treats, prevents, cures or manages any disease or condition. Sidr & Stone does not sell black currant seed oil. Black seed oil is a food supplement, not a medicine, and is not a substitute for medical treatment of any condition. For any health concern, or before adding a supplement to existing medication, consult a qualified medical professional.