Black seed oil (Nigella sativa)

What black seed oil is

Black seed oil is pressed from the seeds of Nigella sativa, true black cumin. Botanically, the plant is not related to culinary caraway. It is sold as seeds for use as a spice, as cold-pressed oil and as capsules containing oil or seed powder.

The oil contains an essential oil with terpenes, thymoquinone and beta-elemene. Thymoquinone in particular is studied. In the human studies, however, seed powder or oil was almost always given, not the isolated compound.

How it works

How black cumin might act on blood pressure and blood sugar has not been clarified in humans. Alongside the metabolic values, the large meta-analysis also found lower inflammatory markers such as CRP, IL-6 and TNF-α as well as changes in markers of oxidative stress. This fits with an anti-inflammatory effect but is not proof of the mode of action.

A plausible mechanism is not yet a clinical benefit. The studies measured laboratory values and blood pressure, that is, surrogate markers.

What the studies show

82 trials on cardiovascular risk factors

Jafari 2025 analyzed 82 randomized trials with 5,026 participants, amounts of 200 to 4,600 mg per day and durations of 1 to 48 weeks, and rated the certainty of evidence with GRADE. Improvements were seen in, among others, body fat percentage, body mass index, waist circumference, systolic and diastolic blood pressure, fasting glucose, HbA1c, LDL, HDL, triglycerides, CRP and IL-6. The authors see black cumin as a possible adjunct for improving risk factors.

Metabolic disorders: small, measurable effects

Musazadeh 2026 limited itself to 31 trials with 2,145 people with metabolic disorders such as type 2 diabetes or overweight. Weight fell by 1.59 kg, body mass index by 0.51, blood pressure by 3.25 over 2.75 mmHg, fasting glucose by 18.6 mg/dl and HbA1c by 0.56 percentage points. Waist circumference, insulin and insulin resistance did not change. The authors speak of modest improvements and urge caution because of the variable quality of the trials.

Blood lipids and blood sugar: large values, large scatter

Rounagh 2024 found, across 34 trials with 2,278 adults, lower values for total cholesterol, LDL and triglycerides and a higher HDL. The results are given as standardized mean differences, which are unusually large at up to −2.45 for LDL. For blood sugar, Shirvani 2024 showed a similar picture across 30 trials, with heterogeneity of 92.7 percent for fasting glucose and 95.7 percent for HbA1c. Such large scatter means: the individual trials contradict each other considerably on the size of the effect.

Hay fever

He 2024 pooled 8 randomized trials on allergic rhinitis. The response rate was higher under black cumin (odds ratio 4.24), and in three trials nasal symptoms decreased more. Adverse effects were transient and no more frequent than in the control groups. The authors themselves name the small number and low quality of the trials as a weakness.

Where the data stop

• Heart attack, stroke, lifespan. No trial has measured hard endpoints. Whether the small improvements in risk factors change anything about them is open.
• Long-term data. The trials ran for 48 weeks at most.
• The size of the effect. Heterogeneity for blood sugar is above 90 percent; the pooled values are therefore uncertain.
• Insulin resistance and belly fat. Both remained unchanged in the analysis of metabolic disorders.
• A remedy for almost everything. For the many other uses for which black seed oil is promoted, there is no comparable body of studies. As a galactagogue during breastfeeding, the effect is not established.

Status, approval and legal

In Germany, black cumin and its oil are foods; capsules are sold as food supplements. There is no official maximum amount. Black cumin does not appear in the list of health claims authorized by the EU, Regulation (EU) No 432/2012. Advertising statements on blood pressure, blood sugar or cholesterol are therefore not covered by an authorized claim.

Safety

In the trials, adverse effects were rare and transient. Outside the trials, serious individual cases have been described: a case series of 8 people with severe skin reactions after applying black seed oil, a blistering skin reaction resembling Stevens-Johnson syndrome after taking a preparation, and acute kidney failure with muscle breakdown and liver damage after black seed oil. Allergic contact dermatitis is known. For breastfeeding, data on safety for infants are lacking.

Because the trials show precisely a lowering of blood sugar and blood pressure, taking it alongside corresponding medicines should be discussed with a doctor. In the BK-Score, safety stands at 5 out of 10; this axis measures how well safety has been studied, not how safe the substance is. This text is information and does not replace medical advice.

Sources

• Jafari A et al., Pharmacol Res 2025 – meta-analysis, 82 randomized trials, cardiovascular risk factors
• Musazadeh V et al., Endocrinol Diabetes Metab 2026 – meta-analysis, 31 trials in metabolic disorders
• Rounagh M et al., Clin Nutr ESPEN 2024 – meta-analysis, 34 trials, blood lipids
• Shirvani S et al., Prostaglandins Other Lipid Mediat 2024 – meta-analysis, 30 trials, blood sugar
• He Y et al., Front Pharmacol 2024 – meta-analysis, 8 trials, allergic rhinitis
• Zhivov E et al., J Clin Aesthet Dermatol 2024 – case series, 8 severe skin reactions after topical use
• Chu B et al., JAAD Case Rep 2026 – blistering skin reaction after taking a Nigella sativa preparation
• Sener K et al., Toxicon 2024 – case report, muscle breakdown and acute kidney failure after black seed oil
• LactMed (NIH) – Black Seed, breastfeeding and tolerability
• Regulation (EU) No 432/2012 – list of permitted health claims made on foods