Black Seed

Nigella sativa L. is an annual herb in Ranunculaceae, the buttercup family; NCBI Taxonomy files it as taxon 555479, under the common name black cumin. Hannan and colleagues (Nutrients 2021) describe it as growing 20–30 cm tall, with linear leaves, bluish flowers, capsule-shaped fruits, and small black seeds that resemble cumin, hence the name. The garden flower love-in-a-mist, Nigella damascena, belongs to the same genus. Hannan and colleagues give the plant’s native range as a vast region of the eastern Mediterranean, northern Africa, the Indian subcontinent, and south-west Asia, and list Egypt, Iran, Greece, Syria, Albania, Turkey, Saudi Arabia, India, and Pakistan among the countries that cultivate it. The seeds are the part used, whole or ground, or pressed for oil.

The names cause real confusion. MSKCC lists black cumin, black caraway, black seed, and kalonji as common names, and Hannan and colleagues note the Arabic name habbat al-barakah, blessed seed. But true cumin is Cuminum cyminum, a member of the carrot family (Apiaceae), and the name black cumin is also used for Bunium persicum, an Apiaceae spice sold in South Asia as kala zeera; a 2011 cytogenetic study of that plant is titled with the words black cumin. Recipes, shop labels, and even some research papers mix these plants up. For medicinal purposes, the only reliable identifier is the botanical name Nigella sativa. Products include whole seed, ground seed in capsules, cold-pressed seed oil, honey-and-seed mixtures, and concentrated extracts.

Thymoquinone (PubChem CID 10281, C10H12O2) is the compound most researchers focus on: Hannan and colleagues describe it as the main bioactive component of the seed’s essential oil, and MSKCC also names nigellone, a constituent of crude extracts. Gaudin and colleagues (JAMA Dermatology 2018) analysed one patient’s black seed oil and found mainly terpenes, thymoquinone, linoleic acid, and other fatty acids, with p-cymene among the terpenes. Composition varies a great deal. A 2022 safety assessment by Burdock and colleagues (Regulatory Toxicology and Pharmacology) reported widely variable results for the volatile fraction, which it attributed to crop origin, possible varietal differences, contamination or adulteration, extraction method, and seed maturity. Hannan and colleagues note that thymoquinone has poor bioavailability, so laboratory results with the pure compound may say little about what a capsule delivers.

Black seed has deep roots in the ancient Near East. Among Howard Carter’s records of Tutankhamun’s tomb, now published by the Griffith Institute at the University of Oxford, a 1933 botanical report identifies black cumin (Nigella sativa), also called gith, and notes that seeds of the species were present in one sample from the tomb. That is a single find, and claims that black seed was a staple of Egyptian medicine or mummification go well beyond it. Burdock and colleagues describe a three-millennial history of use as a food ingredient in Middle Eastern and Far Eastern cultures. Hannan and colleagues write that Hippocrates and Dioscorides knew the seed as melanthion, and that Avicenna’s Canon of Medicine credited it with restoring energy and relieving tiredness.

Its special status in Islamic tradition comes from the hadith. In Sahih al-Bukhari, in the book of medicine, Abu Huraira reports hearing the Prophet say, “There is healing in black cumin for all diseases except death.” The narrator Ibn Shihab adds that the word translated as death is al-sam, and that the black seed meant is shuniz, another name for nigella. For many Muslims this saying gives black seed a place in what is often called prophetic medicine (al-Tibb al-Nabawi), and Hannan and colleagues note that it has long been prescribed in the Unani, Ayurveda, and Tibb systems. The hadith is a statement of faith and tradition; it is not a clinical claim, and it does not mean black seed can replace medical treatment for any illness.

Traditional uses are broad. Hannan and colleagues list asthma, bronchitis, rheumatism, headache, back pain, loss of appetite, amenorrhoea, paralysis, inflammation, eczema, and high blood pressure, along with topical use of the oil on the skin. The US National Library of Medicine’s LactMed database notes that black seed and a related species have been used to increase breast milk supply in India, Türkiye, and the Middle East. Laboratory work on the seed and thymoquinone was under way by the 1990s, as MSKCC’s reference list shows, and was followed by a wave of small clinical trials, including many in Saudi Arabia and Iran. By the late 2010s enough trials existed for meta-analyses of blood glucose, lipids, blood pressure, asthma, and weight, and Burdock and colleagues concluded in 2022 that the seed, at historical levels of food use, is safe.

Most mechanistic evidence comes from cells and animals. MSKCC summarises studies in which thymoquinone acted as an antioxidant, restoring glutathione and superoxide dismutase levels in animal models, and in which black seed oil reduced inflammatory signalling by inhibiting cyclooxygenase and lipoxygenase, the enzymes that make prostaglandins and leukotrienes. Nigellone inhibited histamine release from rat mast cells, which is the usual rationale for trials in asthma and allergy. In rats, black seed lowered blood pressure, probably through a diuretic effect, and in mice the oil lowered blood glucose, triglycerides, and cholesterol and also reduced platelet and white cell counts (MSKCC). Hannan and colleagues review animal studies attributing glucose lowering to increased insulin secretion and reduced oxidative stress.

Translating this to people is uncertain. Thymoquinone is poorly bioavailable, products vary widely in composition, and the doses used in animals are often far higher than human intakes or given by injection. Hannan and colleagues show how much the route matters: in rats and mice, the lethal dose of thymoquinone was roughly 795–871 mg/kg by mouth but 57–105 mg/kg by injection into the abdomen. The anticancer effects MSKCC describes, including inhibition of DNA synthesis and promotion of cell death in tumour cells, come from laboratory and animal models only. MSKCC also notes that the antioxidant effects that might protect healthy tissue from radiation could, in theory, protect cancer cells too, and that it is not known whether black seed makes radiotherapy less effective.

Black seed also affects drug handling. Al-Jenoobi and colleagues (Drug Metabolism Letters 2010) found that black seed extract inhibited the liver enzymes CYP2D6 and CYP3A4 in human liver microsomes and, in four healthy volunteers who took 2.5 g of seed twice daily for a week, changed urinary markers of the metabolism of the probe drug dextromethorphan in the same direction. Wang and colleagues (Chemico-Biological Interactions 2022) found that thymoquinone competitively inhibited the CYP2C9-mediated breakdown of warfarin in the laboratory and predicted that more than 1 g a day of seed or oil might alter warfarin levels. In rabbits, black seed lowered blood levels of cyclosporine, an anti-rejection drug (Al-Jenoobi and colleagues, BioMed Research International 2013).

Blood glucose in type 2 diabetes: Daryabeygi-Khotbehsara and colleagues (Complementary Therapies in Medicine 2017) pooled seven trials in people with type 2 diabetes. Black seed lowered fasting blood glucose by about 18 mg/dl and HbA1c by 0.71 percentage points, and also lowered total and LDL cholesterol; effects on triglycerides and HDL cholesterol were not significant, and there was evidence of publication bias for HbA1c. In one of the better-known trials, Bamosa and colleagues (Indian Journal of Physiology and Pharmacology 2010) gave 94 people with type 2 diabetes capsules of 1, 2, or 3 g of seed a day for three months, added to their usual tablets. At 2 g a day, HbA1c fell by 1.52 percentage points from baseline; 1 g produced non-significant trends and 3 g added nothing. The trial had no placebo group, so some of that fall may reflect closer attention during the study. MSKCC describes the diabetes evidence as small studies showing benefit.

Cholesterol and blood pressure: Sahebkar and colleagues (Pharmacological Research 2016) pooled 17 randomised controlled trials and found that black seed lowered total cholesterol by about 16 mg/dl, LDL cholesterol by 14 mg/dl, and triglycerides by 21 mg/dl, with no overall effect on HDL; seed oil had larger effects on total and LDL cholesterol than seed powder. A companion meta-analysis (Journal of Hypertension 2016) pooled 11 trials with 860 people and found reductions of 3.3 mmHg in systolic and 2.8 mmHg in diastolic blood pressure compared with control after an average of about eight weeks, with powder doing better than oil. These are modest effects in short trials, MSKCC calls the blood pressure data conflicting, and no trial has shown fewer heart attacks or strokes.

Asthma: Koshak and colleagues (Phytotherapy Research 2017) randomised 80 adults with asthma to black seed oil capsules, 500 mg twice daily, or placebo for four weeks alongside their usual treatment. The Asthma Control Test score was modestly better with the oil (21.1 versus 19.6) and blood eosinophils, a marker of allergic inflammation, fell; lung function improved slightly but not significantly, and ten people dropped out of each group. He and Xu (American Journal of Emergency Medicine 2020) pooled just four trials and found improved asthma control scores and FEV1, but no clear effect on peak flow. MSKCC says black seed may help prevent asthma symptoms. It is an add-on that has been tested for weeks, not a substitute for inhalers.

Weight: Namazi and colleagues (Journal of Ethnopharmacology 2018) pooled 11 placebo-controlled trials and found that black seed reduced body weight by about 2.1 kg, body mass index by 1.2 kg/m², and waist circumference by 3.5 cm. The authors called the effect moderate, warned that heterogeneity for body weight was high and high-quality trials few, and noted that no serious side effects were reported. A difference of two kilograms over a few weeks or months is small, and the trials were too short to show whether any loss is maintained.

Other uses: MSKCC lists small trials suggesting benefit in rheumatoid arthritis, allergic symptoms, functional dyspepsia, Helicobacter pylori infection, and fatty liver disease; topical oil for cyclical breast pain and knee osteoarthritis; a gel that reduced the severity of radiation dermatitis in women with breast cancer; and fewer episodes of febrile neutropenia in children with brain tumours. In knee osteoarthritis, oral seed powder did not help, although oral oil did in another trial. A pilot study of thymoquinone in children with drug-resistant epilepsy is also listed. LactMed notes that no scientifically valid clinical trials support black seed as a galactogogue to increase milk supply. All of these findings need larger, independent trials.

There is no standard medicinal dose. Clinical trials have used ground seed in capsules at 1–3 g a day, with 2 g a day the most effective dose in the Bamosa diabetes trial; seed oil at 500 mg twice daily in the Koshak asthma trial; and 2.5 g of seed twice daily for a week in the Al-Jenoobi interaction study. Most trials lasted between a few weeks and three months, so longer-term effects of supplement doses are unknown. Hannan and colleagues describe a small study in which people with Helicobacter pylori took a mixture providing 6 g of ground seed and 12 g of honey a day for two weeks. Use as a cooking spice involves much smaller amounts, which Burdock and colleagues consider safe at historical levels of consumption.

Quality is a genuine problem. Burdock and colleagues report widely variable composition between samples, and LactMed notes that dietary supplements in the United States do not need pre-marketing approval, that labelled and actual contents often differ, and that results from one product may not apply to another. Choose products that name Nigella sativa, state whether they contain seed powder or oil, and give the amount per dose. Seed powder and oil are different products, and a result from a trial of one does not automatically apply to the other. Independent quality certification confirms content, not safety or effectiveness.

Applying black seed oil to the skin, including in hair and beard products, is a common source of allergic reactions. MSKCC notes that topical use of pure oil has caused allergic reactions, and the severe cases described by Gaudin and colleagues all followed use of the oil on the skin. Do not apply the oil to large areas or broken skin, stop at the first sign of a rash, and seek urgent care for blistering, peeling, fever, or a rash spreading beyond the area of use. If you take black seed regularly alongside any medicine, tell your prescriber and pharmacist, and do not take more than the doses used in trials.