Black Seed Oil and Testosterone: What the Trials Actually Measured
Search for black seed oil and testosterone and you will find the claim stated as settled fact, usually with a study reference attached. The reference is real. What it says is not what the pages citing it say. We went back to the primary literature, and the position is narrower and more interesting than the summaries suggest: exactly one randomised controlled trial has measured serum free testosterone in men taking Nigella sativa, and in that trial the figure fell in both the treatment and the placebo arms, without reaching statistical significance in either. Every study reporting an increase was done in rats.
For our own oil, see our cold-pressed Ethiopian black seed oil.
The Short Answer
- The only randomised controlled trial to measure serum free testosterone in men taking Nigella sativa is Datau EA et al., Acta Medica Indonesiana 2010;42(3):130–4 (PMID 20724766). Free testosterone fell in both arms, and the reduction was not statistically significant in either.
- The other human trial routinely cited in this context — Kolahdooz M et al., Phytomedicine 2014;21(6):901–5 (PMID 24680621) — did not measure serum testosterone at all. It measured semen parameters.
- In the largest recent human trial to measure testosterone in any population, serum testosterone went down significantly in the Nigella sativa arm (Mahmoudian A et al., Journal of Ovarian Research 2024;17(1):144, PMID 38997723, p=0.001) — the opposite direction to the popular claim.
- The studies reporting increased testosterone are rodent studies. One of them (Leisegang K et al., PMID 33378981) also found that the higher dose negatively affected sperm viability (P=0.047).
- Across the wider literature, an umbrella review of twenty meta-analyses graded 88 of 110 outcome measures as very low certainty (Li Z et al., Frontiers in Nutrition 2023;10:1107750, PMID 37057067).
- Sidr & Stone publishes a specific, independently verified figure of 2.67% thymoquinone, tested per batch by Analytice, an ISO-accredited French laboratory — a measured number about what is in the bottle, not a claim about hormones.
What the One Trial That Measured Testosterone in Men Found
Datau EA and colleagues ran a double-blind, placebo-controlled trial in men aged 30 to 45 with central obesity, published in Acta Medica Indonesiana in 2010 (42(3):130–4, PMID 20724766). Participants took Nigella sativa or placebo for three months, and serum free testosterone was among the outcomes recorded. This remains the only randomised controlled trial we can find in which that measurement was taken in men.
The result is the part that gets left out. Free testosterone declined in both groups over the three months. Neither decline reached statistical significance. The difference between arms was that the fall was smaller in the Nigella sativa group — a smaller decrease, not an increase, and not a statistically significant one. Citing this trial as evidence that black seed oil raises testosterone is a misreading of its own reported outcome.
| Trial | Population | Duration | Was testosterone measured? | Result |
|---|---|---|---|---|
| Datau EA et al., Acta Med Indones 2010;42(3):130–4 (PMID 20724766) | Men 30–45, central obesity | 3 months | Yes — serum free testosterone | Fell in both arms; not significant in either |
| Kolahdooz M et al., Phytomedicine 2014;21(6):901–5 (PMID 24680621) | 68 men with infertility | 2 months | No | Semen parameters only |
| Mahmoudian A et al., J Ovarian Res 2024;17(1):144 (PMID 38997723) | 114 adolescent females with PCOS | 16 weeks | Yes — serum testosterone | Decreased significantly in the Nigella sativa arm (p=0.001) |
The Other Study People Cite Never Measured Testosterone
Kolahdooz M and colleagues (Phytomedicine 2014;21(6):901–5, PMID 24680621) gave 2.5 ml of black seed oil twice daily for two months to 68 men with infertility. The trial is frequently cited in testosterone discussions, and it is a real randomised trial with a real result set. But the outcomes recorded were sperm count, sperm motility, sperm morphology, semen volume, semen pH and round cell count. Serum testosterone was not among them.
This is a specific and common failure mode: a paper about male reproductive health gets summarised as a paper about testosterone, because the two sit close together in the reader's mind. They are different measurements answering different questions, and a study that never took a blood hormone level cannot tell you what happened to one.
In the Largest Recent Trial, Testosterone Went Down
The most substantial recent human data on Nigella sativa and testosterone comes from a population that is rarely mentioned in the men's-health framing. Mahmoudian A and colleagues (Journal of Ovarian Research 2024;17(1):144, PMID 38997723) randomised 114 adolescent females with polycystic ovary syndrome to Nigella sativa 1000 mg daily or a hormonal comparator (medroxyprogesterone) for sixteen weeks, and measured serum testosterone.
Testosterone decreased significantly more in the Nigella sativa arm (p=0.001). In the clinical context of PCOS, where elevated androgens are part of the picture, a reduction is what the researchers were looking for. For our purposes here, the relevant point is directional: the best-powered recent human measurement of testosterone under Nigella sativa found it going down, not up. That is difficult to reconcile with a supplement marketed on the opposite premise.
Our page on black seed oil and women's health covers the PCOS literature in more depth.
The "Increases Testosterone" Findings Come From Rats
There are studies reporting increased testosterone under Nigella sativa, and it is worth being precise about what they are. Leisegang K and colleagues (Biomedicine & Pharmacotherapy 2021;133:111085, PMID 33378981) worked with 54 Wistar rats on a high-sugar diet and reported improved testosterone at 200 and 400 mg/kg against the high-sugar saline control (P<0.001). The same paper also reported that the 400 mg/kg dose negatively affected sperm viability (P=0.047) — a detail that does not survive the journey into supplement copy.
Sadeghimanesh A and colleagues (Biomedicine (Taipei) 2021;11(1):19–25, PMID 35223391) used a castrated rat model of benign prostatic hyperplasia and reported reductions in prostatic index, prostate volume, dihydrotestosterone and PSA at 400 and 800 mg/kg. Both are legitimate animal experiments. Neither is a human result, and a rodent dose in mg per kilogram of body weight is not a spoonful of oil.
| Study | Model | Reported on testosterone | Also reported |
|---|---|---|---|
| Leisegang K et al., Biomed Pharmacother 2021;133:111085 (PMID 33378981) | 54 Wistar rats, high-sugar diet | Improved at 200 and 400 mg/kg (P<0.001) | 400 mg/kg negatively affected sperm viability (P=0.047) |
| Sadeghimanesh A et al., Biomedicine (Taipei) 2021;11(1):19–25 (PMID 35223391) | Castrated rats, BPH model | Reduced dihydrotestosterone | Reduced prostatic index, prostate volume, PSA, MDA |
| Datau EA et al. (PMID 20724766) | Humans — men 30–45 | Fell in both arms, not significant | The only human free-testosterone measurement available |
How Strong Is the Evidence Base, Overall?
The testosterone question is not unusually weak; it reflects the field. Li Z and colleagues (Frontiers in Nutrition 2023;10:1107750, PMID 37057067) ran an umbrella review of twenty meta-analyses covering 110 outcome measures and graded 88 of them very low certainty, 17 low and just 5 moderate. Hallajzadeh J and colleagues (Phytotherapy Research 2020;34(10):2586–2608, PMID 32394508) pooled fifty randomised trials of inflammatory and oxidative markers and found null results across CRP, TNF-α, total antioxidant capacity and MDA.
There is also a supply-side problem that undercuts any dose-response reasoning. Khaikin E and colleagues (Nutrients 2022;14(17):3501, PMID 36079759) measured eleven commercial black seed oil products and found thymoquinone spanning 3.08 to 809.4 mg per 100 g. Two bottles labelled the same way can differ by more than two hundred-fold in the compound the research is about.
| Source | What was assessed | Finding |
|---|---|---|
| Li Z et al., Front Nutr 2023;10:1107750 (PMID 37057067) | 20 meta-analyses, 110 outcome measures | 88 very low, 17 low, 5 moderate certainty |
| Hallajzadeh J et al., Phytother Res 2020;34(10):2586–2608 (PMID 32394508) | 50 randomised trials, inflammatory markers | Null for CRP, TNF-α, total antioxidant capacity and MDA |
| Khaikin E et al., Nutrients 2022;14(17):3501 (PMID 36079759) | 11 commercial products | Thymoquinone 3.08–809.4 mg per 100 g |
For a fuller walkthrough of what separates one bottle from another, see our guide to choosing a quality black seed oil.
The Objections Worth Taking Seriously
"A smaller decline is still a relative benefit." It might be, and we are not dismissing it. But the Datau trial reported that neither decline reached statistical significance, which means the difference between the arms cannot be distinguished from chance at the sample size used. A signal worth investigating is not the same as a finding, and treating it as one is exactly how the claim got out of hand.
"Rat data has to count for something." It counts as a reason to run a human trial. It does not count as a human result. The Leisegang paper is a good illustration: the same experiment that produced the testosterone finding also produced an adverse sperm-viability finding at the higher dose, and any honest reading has to carry both.
"So is there any reason to take it?" There are reasons — it is a whole food oil with a long traditional history and a genuinely interesting research programme around thymoquinone. Raising testosterone is not among the reasons the evidence supports. If low testosterone is a concern, that is a clinical question with a blood test attached, and it belongs with your GP rather than with a supplement shelf.
Why Sidr & Stone
This article has spent most of its length taking a claim apart. It would be inconsistent to close by making one. So we will tell you what we can verify rather than what we would like to imply.
- Independently verified 2.67% thymoquinone, tested per batch
- Tested by Analytice, an ISO-accredited French laboratory
- Organically grown Ethiopian highland Nigella sativa — chosen after a 36-supplier evaluation
- Cold-pressed below 40°C to protect the heat-sensitive thymoquinone
- 100% pure — single ingredient, nothing added
- Unrefined and unfiltered — natural fine sediment is normal
- Bottled in matte black UV-protective glass
- Halal certified
- 10% of profits to charity
- Fulfilment in the UK, EU, and US
We will not tell you Sidr & Stone is the strongest or the best — that would be the very kind of claim this article warns against. What we will say is that our thymoquinone figure is 2.67%, independently verified per batch, and the evidence is there to see.
Frequently Asked Questions
Does black seed oil increase testosterone?
The published human evidence does not show that. In the only randomised controlled trial that measured serum free testosterone in men (Datau EA et al., PMID 20724766), the figure fell in both the treatment and placebo arms and the change was not statistically significant in either.
Which studies do the "testosterone booster" claims actually come from?
Mostly rat studies — principally Leisegang K et al. (PMID 33378981) and Sadeghimanesh A et al. (PMID 35223391). Rodent findings at a dose in mg per kilogram are a reason to run a human trial, not a human result.
Did the infertility trial measure testosterone?
No. Kolahdooz M et al. (Phytomedicine 2014, PMID 24680621) measured sperm count, motility, morphology, semen volume, pH and round cells in 68 men. Serum testosterone was not an outcome in that trial.
Why did testosterone go down in the PCOS trial?
In Mahmoudian A et al. (Journal of Ovarian Research 2024, PMID 38997723), 114 adolescent females with PCOS took Nigella sativa for sixteen weeks and serum testosterone decreased significantly (p=0.001). Reducing elevated androgens is a clinical goal in PCOS, so the researchers were looking for that direction.
How do I check whether a black seed oil is any good?
Ask for a per-batch thymoquinone figure with a named laboratory behind it, rather than a range or an "up to" number on the label. Product-to-product variation is very large — 3.08 to 809.4 mg per 100 g across eleven products in one published analysis.
What dose was used in the human trials?
Datau EA et al. used a three-month Nigella sativa course in men with central obesity; Kolahdooz M et al. used 2.5 ml of oil twice daily for two months. Neither is a recommendation — see our page on black seed oil dosage for general guidance.
Where can I buy a black seed oil with a published thymoquinone figure?
Ours is verified at 2.67% thymoquinone per batch by Analytice and is available with fulfilment in the UK, EU, and US. Whichever brand you choose, ask to see the per-batch result.
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 interesting thing about this claim is not that it is unsupported. It is that the evidence points the other way, and the study most often cited in its favour reports the opposite of what it is said to report. One trial measured free testosterone in men and found it falling in both arms. One trial in a different population measured testosterone and found it falling significantly under Nigella sativa. The upward findings are all in rodents, and the paper that produced the clearest one also flagged an adverse effect on sperm viability at the higher dose.
None of that is a reason to think badly of black seed oil. It is a reason to be careful about which promises get attached to it. If low testosterone is genuinely a concern, that is a blood test and a conversation with your GP, not a bottle. If you want a well-made, single-ingredient oil with a verified figure on the label, that is a different and entirely reasonable thing to want.
Our cold-pressed Ethiopian black seed oil — independently verified at 2.67% thymoquinone — is available now, with fulfilment in the UK, EU, and US.
Shop Sidr & Stone Cold-Pressed Ethiopian Black Seed Oil — Verified 2.67% Thymoquinone →
This article describes the published research on Nigella sativa and testosterone measurement at the time of writing; research findings may change, and readers should check current sources. 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, including concerns about hormone levels, consult a qualified medical professional.