Black Cumin (Nigella sativa L.)
1. Identity, Botanical Classification, and Common Names
Nigella sativa (common names: black caraway, black cumin, nigella, charnushka, or kalonji) is an annual flowering plant in the family Ranunculaceae, native to western Asia (the Levant, Cyprus, Turkey, Iran, and Iraq), and eastern Europe (Bulgaria and Romania). It is naturalised over parts of Europe, North Africa, and east to Myanmar. The genus name Nigella is a diminutive of the Latin niger, "black," referring to the colour of the seeds, and the specific epithet sativa means "cultivated."
In food preparation, Nigella sativa and its seeds are variously called black caraway, black seed, black cumin, charnushka, fennel flower, nigella, nutmeg flower, Roman coriander, or black onion seed. In Arabic traditional medicine contexts, it is known by names including black cumin seed, black seed, Habbatul Barakah, Habbatus sawda, and Kalonji. It should be noted that black seeds (Nigella sativa), which are totally unrelated to Cuminum cyminum, have nevertheless taken the name "black cumin" and are used in traditional systems of medicine for many disorders.
Black cumin plants are hardy annuals that grow from 20 to 60 cm in height. The branched stems bear deeply divided fine leaves, and the plant has a developed taproot. The pale blue or white flowers have five petals, numerous stamens, and five or six elongated fused carpels. The black triangular or pyramidal seeds are borne in a capsule with five or six segments, each of which terminates in an elongated projection.
Forms and Preparations
- Whole seeds: Used directly as a spice and in traditional preparations, consumed raw, ground, or roasted.
- Cold-pressed fixed oil (black seed oil / BSO): The plant contains fixed oil (FO, 36–38%), carbohydrates, proteins, fiber, minerals, volatile oil (0.2%), and essential oil (0.4–2.5%), as well as alkaloids, coumarins, and saponins.
- Essential/volatile oil: Extracted by steam distillation; concentrated in thymoquinone and monoterpenes.
- Encapsulated seed powder and oil: Used in clinical studies in the form of 500 mg oral capsules.
- Aqueous extracts and decoctions: Used in traditional and some clinical settings.
- Topical preparations: Oils and gels applied to skin for dermatological uses.
2. Traditional and Historical Use
For more than 2,000 years, N. sativa seeds and oil have been utilized in traditional medicine. In Indian and Middle Eastern traditional medicine systems, including Unani and Ayurveda, N. sativa seeds and their oil have been used for centuries both as a dietary component and a therapeutic agent. In Islamic tradition, its medicinal value is emphasized in Prophetic Medicine, where it is described as a remedy for a wide range of ailments, contributing to its continued use and reverence among Muslim communities.
N. sativa is included in the list of natural drugs in different medicines including Tibb-e-Nabavi (the Medicine of Prophet Mohammad), Unani Tebb, and Indian traditional medicine. In traditional remedy, N. sativa seeds are commonly used as a spice and carminative.
The medicinal properties of N. sativa seeds were acknowledged in Greco-Roman civilization, with references in the works of Dioscorides, a renowned Greek physician and botanist. It has been found in Egyptian pharaoh tombs, suggesting that it was used as far back as ancient Egypt.
In Ayurveda, the traditional Indian medical system, N. sativa seeds found application in treating various ailments, including digestive issues, respiratory conditions, and skin disorders. Traditional Chinese medicine incorporated N. sativa seeds for their anti-inflammatory, diuretic, and digestive properties, contributing to their historical use in this medical tradition.
In traditional remedy, several properties such as liver tonics, diuretics, digestive, and anti-diarrheal uses were ascribed to the plant. It has also been used to treat diseases including asthma, hyperglycemia, urine retention, hypertension, inflammation, cough, and pain. Sometimes hailed as a panacea, black cumin seeds and their oil are widely used in traditional Islamic medicine and Ayurveda to treat a variety of ailments.
Since it became popular in the seventh century, there has never been a period in Islamic history when its use was ever banned. The Prophet Muhammad is reported to have said, "Hold on to the use of the black seed for indeed it has a remedy for every illness except death." This powerful endorsement has made black cumin a staple in Islamic medicine for centuries.
3. Key Constituents and Active Compounds
3.1 Volatile (Essential) Oil Fraction
Thymoquinone (TQ) and its derivatives — such as carvacrol, 4-terpineol, α-pinene, thymol, t-anethol, thymohydroquinone (THQ), dithymoquinone, p-cymene, and sesquiterpene longifolene — constitute the terpenes and terpenoids family, which is the major chemical group of black cumin.
Thymoquinone is the main and most abundant (27.8–57.0%) compound of N. sativa seeds' essential oil, and the other components, such as carvacrol (5.8–11.6%), 4-cymene (7.1–15.5%), 4-terpineol (2.0–6.6%), t-anethole (0.25–2.3%), and longifolene (1.0–8.0%), exist at lower amounts.
Thymoquinone, a monoterpene molecule, is chemically known as 2-methyl-5-isopropyl-1,4-benzoquinone. It is abundantly present in seeds of Nigella sativa L., popularly known as black cumin or black seed, which belongs to the family Ranunculaceae. Thymoquinone has been reported to possess potent lipophilicity and limited bioavailability, and exhibits light and heat sensitivity.
3.2 Fixed Oil Fraction
The N. sativa seeds contain 36–38% fixed oil and 0.4–2.5% essential oil. The fixed oil is mainly composed of unsaturated and essential fatty acids (linoleic acid, followed by oleic acid), whereas the volatile oil has been shown to contain 18.4–24% thymoquinone and 46% monoterpenes such as p-cymene and pinene. Besides the fatty acid profile, it also consists of considerable quantities of vitamin E (tocopherols α, β, and γ), retinol (vitamin A), carotenoids (β-carotene), and thymoquinone.
3.3 Alkaloids
The main bioactive components of N. sativa seeds include thymoquinone, carvacrol, 4-cymene, pentacyclic triterpenoid saponins (α-hederin), and alkaloids: nigellicine, nigellicimine, nigellicimine-N-oxide, and nigellidine. Significant alkaloids distinguished in Nigella sativa are the pyrazole alkaloids (nigellicine and nigellidine) and isoquinoline alkaloids (nigellicimine and nigellicimine-N-oxide).
3.4 Other Notable Constituents
N. sativa seeds contain a complex of more than 100 compounds, some of which have not yet been studied or even identified. Unsaturated fatty acids in the fixed oil and essential oil components — especially thymoquinone, dithymoquinone, thymohydroquinone, thymol, alkaloids, saponins, vitamins, as well as trace elements — contribute to its health benefits. Seeds also contain carbohydrates, fats, vitamins, proteins, and essential amino acids.
The phytochemical composition of black cumin varies depending on the growing regions, maturity stage, processing methods, and isolation techniques.
4. Mechanisms of Action
4.1 Antioxidant Mechanisms
N. sativa has protective effects against oxidative stress via different mechanisms including inhibition of lipid peroxidation, increment in total thiol content and glutathione level, radical scavenging, and increasing the activity of superoxide dismutase, glutathione transferase, glutathione peroxidase, and catalase. TQ has a strong antioxidant potential due to its free radical scavenging activity.
4.2 Anti-inflammatory Mechanisms
TQ exerts its anti-inflammatory and antioxidant effects via several molecular pathways, including the release of cytokines, and activation of cyclooxygenase-2 (COX-2), nuclear factor erythroid 2–related factor 2 (Nrf2), phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT), and nuclear factor kappa-light-chain-enhancer of activated B (NF-κB).
Thymoquinone modulates inflammatory pathways by downregulating cytokines such as TNF-α, IL-1β, and IL-6, and inhibiting cyclooxygenase (COX) and lipoxygenase (LOX) enzymes. Thymoquinone has been shown to reduce pro-inflammatory mediators in inflamed tissue, including IL-1, TNF-α, IL-6, MCP-1, C-reactive protein, myeloperoxidase, and NF-κB.
4.3 Immunomodulatory Mechanisms
The pleiotropic pharmacological effects of black cumin, and its main bioactive component thymoquinone, have been manifested by their ability to attenuate oxidative stress and inflammation, and to promote immunity, cell survival, and energy metabolism. Nuclear factor κB (NF-κB) comprises a family of ubiquitously expressed, eukaryotic transcription factors critically involved in inflammatory signalling. Besides their well-documented anti-tumor and anti-microbial properties, the anti-inflammatory effects of N. sativa and TQ, both in vitro and in vivo, are evident.
4.4 Signalling Pathway Modulation
Preclinical investigations have demonstrated that thymoquinone modulates key signalling pathways — such as NF-κB, MAPK, and PI3K/AKT — leading to attenuation of oxidative stress, suppression of pro-inflammatory cytokines, and induction of apoptosis in malignant cells. Thymoquinone has also been shown to alter numerous molecular and signaling pathways in many inflammatory and degenerative diseases including cancer.
5. Scientific Evidence by Area of Use
5.1 Glycaemic Control and Type 2 Diabetes
This is among the most extensively investigated clinical areas for N. sativa. Multiple systematic reviews and meta-analyses of RCTs have been conducted.
A meta-analysis that included 17 randomized controlled trials investigating the effects of N. sativa on fasting plasma glucose (FPG), postprandial blood glucose (PPBG), and HbA1c suggested a significant association between N. sativa supplementation and reductions in FPG (weighted mean difference [WMD]: −9.93 mg/dl, 95% CI [−13.44, −6.41]), PPBG (WMD: −14.79 mg/dl, 95% CI [−24.19, −5.39]), and HbA1c (WMD: −0.57%, 95% CI [−0.77, −0.37]).
Nigella sativa was shown across multiple systematic reviews to significantly improve laboratory parameters of hyperglycaemia and diabetes control, with significant falls in fasting blood glucose, blood glucose level 2 h postprandial, glycated haemoglobin, and insulin resistance, and a rise in serum insulin. These findings suggested that Nigella sativa could be used as an adjuvant for oral antidiabetic drugs in diabetes control.
N. sativa was found to be highly potent in terms of its hypoglycaemic activity when compared to placebo, based on improvement in parameters including fasting blood glucose (FBG), postprandial blood glucose (PPBG), HbA1c, HOMA-IR, and HOMA-β. The compound TQ in combination with a daily dose of metformin demonstrated a greater reduction in the levels of HbA1c and blood glucose compared to metformin alone.
A 3-month randomized study was conducted in 60 T2DM patients divided into three groups who received metformin 1 g/day and TQ 50 mg/day, metformin 1 g/day and TQ 100 mg/day, or metformin 1 g/day alone. The two doses of TQ in addition to the hypoglycaemic drug were found to reduce HbA1c, FPG, and PPG to a greater extent than metformin monotherapy.
Evidence strength: Moderate, supported by multiple RCTs and meta-analyses. Most trials are of short duration and modest sample size. There are certain limitations in reporting and methodological quality, and future studies should improve the administration process. The clinical efficacy of N. sativa needs to be confirmed in high-quality, large-sample RCTs to generate more evidence-based clinical practice.
5.2 Lipid Profiles and Cardiovascular Risk
A systematic review on 23 studies demonstrated that N. sativa supplement in different doses and durations can change various clinical and biochemical parameters, including lipid profiles, glycaemic factors, blood pressure, and some anthropometric indices in humans. However, the effect of this supplement is more pronounced on levels of total cholesterol (TC), LDL, fasting blood sugar (FBS), and HbA1c than on triglycerides, HDL, blood pressure, weight, and waist circumference.
In one trial, 88 subjects with total cholesterol values >200 mg/dl received capsules of N. sativa crushed seeds containing 500 mg, or its matching placebo, in two divided daily doses (total daily dose 2.0 g/day) for 4 weeks. Statistically significant decreases in total cholesterol, LDL, and triglycerides were demonstrated with N. sativa treatment.
One trial evaluated the hypolipidaemic effects of N. sativa in 37 menopausal women who received capsulated N. sativa seed powder at 1 g/day or placebo for 2 months. An improvement in the lipid profile was observed, with decreases in TC, LDL-C, and TG and an increase in HDL-C (p < 0.05 for all) compared to placebo.
N. sativa intervention has resulted in significant changes in fasting plasma glucose (FPG), HbA1c, total cholesterol (TC), LDL-C, C-reactive protein (CRP), and malondialdehyde (MDA) in meta-analyses of RCTs.
A single-blind nonrandomized controlled clinical trial on T2D patients given black cumin seed capsules demonstrated a significant decline in TC, LDL-C, TC/HDL-C, LDL-C/HDL-C ratios, diastolic blood pressure, mean arterial pressure, and heart rate, with an increase in serum HDL-C level.
Evidence strength: Moderate for total cholesterol and LDL reduction; weaker for triglycerides and HDL. Most trials are small, short-term, and conducted in populations already at metabolic risk.
5.3 Blood Pressure
A crossover, double-blind, placebo-controlled trial enrolled 39 obese and overweight women to evaluate the effect of N. sativa oil on cardiovascular risk factors. These patients received the supplement at 2 g/day in the form of capsules or a placebo for 8 weeks. N. sativa oil significantly decreased systolic blood pressure (SBP) (p < 0.001) without affecting diastolic blood pressure.
Daily supplementation of N. sativa seed oil in addition to antihypertensive agents appears to be an effective and safe mode for the complementary treatment of hypertension, with an accompanying improvement in lipid and glucose parameters.
Evidence strength: Preliminary to moderate. Effects on blood pressure are less consistently demonstrated than effects on lipids or blood glucose. Trials are small, and the magnitude of effect is modest.
5.4 Respiratory Conditions (Asthma and COPD)
Nigella sativa and its derivatives have been reported to have anti-inflammatory and bronchodilator effects, but the effects have been evaluated in only a few clinical studies.
One single-blind, placebo-controlled, randomized study at an asthma and allergy clinic examined patients divided into three groups. A control group (n=24) received placebo, while NS-1 and NS-2 groups (n=26 each) received 1 and 2 g/day of N. sativa, respectively, for 3 months along with maintenance inhaled therapy.
Other investigations have demonstrated that N. sativa may be an optimal choice for treating patients with allergy-related diseases, such as asthma, atopic eczema, and allergic rhinitis.
In middle-aged adults receiving routine treatment with inhaled corticosteroids for chronic obstructive pulmonary disease, a clinical study showed that taking N. sativa seed oil at 1 g twice daily for 3 months improves lung function measures compared with placebo.
Evidence strength: Preliminary. The available RCTs are small and methodologically heterogeneous. Results are promising but insufficient to draw firm clinical conclusions.
5.5 Liver Health
A randomized, double-blind, placebo-controlled clinical trial investigating N. sativa oil in non-alcoholic fatty liver disease (NAFLD) demonstrated reductions in fasting blood sugar, lipid profiles (TG, TC, LDL, VLDL), liver enzymes (AST and ALT), the hs-CRP inflammatory marker, IL-6, TNF-α, and an increase in HDL-C levels in the interventional group compared to the placebo group. All these compelling pieces of evidence suggest that black cumin preparations and its main active compound TQ are likely to be attractive as a promising therapeutic option against a wide range of liver diseases, including NASH.
A meta-analysis of clinical research shows that taking N. sativa seeds in the form of oil or powder has beneficial effects on levels of alkaline phosphatase (ALP) and aspartate aminotransferase (AST) when used for at least 12 weeks.
Evidence strength: Preliminary to moderate. Data from well-designed trials is limited. Much of the hepatoprotective evidence base consists of animal studies and a small number of clinical trials in specific patient groups.
5.6 Renal Function
In a randomized clinical trial on patients with diabetic nephropathy accompanying chronic kidney disease, following N. sativa oil treatment, there was a significant reduction in blood glucose, serum creatinine, blood urea, and 24-h total urinary protein levels, and an increase in glomerular filtration rate, 24-h total urinary volume, and haemoglobin level.
Evidence strength: Very preliminary. Based on individual trials; more research is needed before conclusions can be drawn.
5.7 Inflammatory Markers and Oxidative Stress
An overview of systematic reviews and meta-analyses suggests that N. sativa has the potential to improve different clinical outcomes, such as blood glucose, inflammatory markers, oxidative stress factors, serum lipids, blood pressure, liver and kidney parameters, and even asthma indicators.
One study showed that N. sativa supplementation led to significant improvements in key haematologic and inflammatory markers, specifically a decrease in WBC count (p = 0.036), CRP (p = 0.023), ESR (p = 0.001), and LDH (p = 0.027).
Evidence strength: Moderate for biomarker effects in at-risk populations. Translation to clinically meaningful outcomes remains to be established in large-scale trials.
5.8 Neurological and Cognitive Effects
A clinical trial performed on healthy adolescent males aged 14 to 17 years established the modulatory effects on cognition, mood, and anxiety of N. sativa taken in the form of a 500 mg capsule once a day for four weeks.
Evidence strength: Very preliminary. The evidence is limited to a small number of trials in specific populations, and findings cannot be generalised.
5.9 Antimicrobial Properties
Various studies on N. sativa have established a broad spectrum of pharmacological actions which include antioxidant, antidiabetic, anticancer, antitussive, immunomodulator, analgesic, antimicrobial, anti-inflammatory, spasmolytic, and bronchodilator properties. Black seed demonstrates antibacterial, antifungal, antiviral, and anti-parasitic properties in preclinical studies, though robust clinical trial evidence for specific antimicrobial indications remains limited.
5.10 Oncology (Preclinical)
TQ is the major active principle of the oil of N. sativa and has been shown to exhibit anti-tumour activity against breast, lung, prostate, liver, colon, and pancreatic cancer in preclinical models. TQ effectively induces apoptosis, inhibits cell proliferation, and reduces metastasis in colorectal cancer cells by modulating key molecular pathways such as PI3K/AKT/mTOR, NF-κB, STAT3, and MAPK.
Evidence strength: Preclinical only (cell line and animal studies). No clinical trials have established therapeutic anti-cancer efficacy in humans as of the available literature.
6. Dosage Forms and Doses Reported in Clinical Studies
In a study by Bamosa et al., patients with type 2 diabetes mellitus were randomly divided into three groups to receive N. sativa seed extracts at 1 g, 2 g, and 3 g per day, respectively, for 12 weeks. Generally, the three doses of N. sativa were well tolerated, with only three patients experiencing mild epigastric discomfort that settled after taking the capsules post meals.
In one 1-year nonrandomized clinical trial on type-2 diabetic patients, N. sativa seeds were provided in the form of 500 mg oral capsules. A dose of 2 grams/day was used, which had already been determined to be effective in reducing blood glucose in a previous study.
In a randomized study on partly controlled asthma patients, NS-1 and NS-2 groups (n=26 each) received 1 and 2 g/day of N. sativa, respectively, for 3 months along with maintenance inhaled therapy.
In one trial, the intervention group received 3 g/day N. sativa oil soft gel capsules (one capsule, three times a day, 30 minutes before each main meal), and the placebo group received similar amounts of sunflower oil for eight weeks.
One trial evaluated the effect of the supplement in 41 T2DM patients who drank N. sativa tea, prepared with one pack containing supplement seeds of 2.5 g, twice daily for 6 months, in addition to their hypoglycaemic drug therapy.
In one trial examining neurological effects, N. sativa was administered in the form of a 500 mg capsule once a day for four weeks.
For COPD, a clinical study used N. sativa seed oil at 1 g twice daily for 3 months.
The doses used across human trials range broadly depending on formulation (whole seed powder, fixed oil, or essential oil), condition, and duration. Doses most commonly reported fall between 1 and 3 g per day of seed or seed oil in capsule form, though standardisation across preparations has not been established in the literature.
7. Safety Considerations and Drug Interactions
7.1 General Tolerability
Administration of N. sativa oil to human volunteers at 5 mL/day for 26 days produced no significant hepatic, renal, or gastrointestinal adverse effects. Seeds at 3 g/day for 3 months consumed by 39 centrally obese subjects did not lead to marked side effects. Similarly, diabetic patients who took N. sativa seeds (1, 2, and 3 g/day for 3 months) showed no significant alterations in renal or hepatic function.
In Bamosa et al.'s dose-ranging study, the three doses of N. sativa were generally well tolerated, with only three patients who experienced mild epigastric discomfort that settled after taking the capsules post meals.
7.2 Adverse Reactions
In one trial using 3 g/day NS oil soft gel capsules, subjects reported no side effects during the intervention except mild gastrointestinal problems.
In one case report of bullous drug eruption, a patient had been taking 2 capsules of black cumin essential oil containing 500 mg of organic N. sativa oil (and 7.5 mg of vitamin E) per day. Such reactions should alert physicians to potentially intense adverse effects of N. sativa essential oils.
7.3 Interaction with Warfarin (CYP2C9)
Thymoquinone, the predominant bioactive compound in N. sativa oil, may inhibit the activity of cytochrome P450 2C9 (CYP2C9). It is not clear from human data whether thymoquinone can affect the pharmacokinetic behaviour of warfarin. In vitro data demonstrated that thymoquinone could inhibit warfarin 7-hydroxylase activity with an IC50 value of 11.35 ± 0.25 μM, and kinetic analysis indicated competitive inhibition with a Ki value of 3.50 ± 0.44 μM. Drug interaction risk prediction suggested that coadministration of thymoquinone (>18 mg/day) or dietary supplements containing thymoquinone (N. sativa >1 g/day or N. sativa oil >1 g/day) might influence the pharmacokinetic behaviour of warfarin. Coadministration of thymoquinone or dietary supplements containing thymoquinone in warfarin-treated patients would likely trigger unexpected potential drug interactions.
7.4 Interaction with Cyclosporine
In a rabbit study, coadministration of N. sativa significantly decreased the Cmax and AUC of cyclosporine — the change was observed by 35.5% and 55.9%, respectively. Concurrent consumption of N. sativa could alter the pharmacokinetics of cyclosporine at various levels. Literature based on in vitro and in vivo investigations suggests that concomitant administration of natural products and prescription drugs may modulate drug pharmacokinetics, which may lead to toxic or subtherapeutic incidences. The incidences of herb-drug interactions are of serious concern especially when the drug has a narrow therapeutic index, for example, warfarin, cyclosporine, and digoxin.
7.5 Potential for Additive Effects with Antidiabetic and Antihypertensive Drugs
N. sativa may interact with blood thinners, diabetes and blood pressure medications, sedatives, and immunosuppressants. Because N. sativa has demonstrated blood glucose-lowering and blood pressure-lowering effects in clinical trials, additive pharmacodynamic effects must be considered when it is used alongside pharmaceutical antidiabetics or antihypertensives.
7.6 Pregnancy
Avoid N. sativa during pregnancy and generally avoid it while breastfeeding. The basis for this caution relates to traditional use of N. sativa as an emmenagogue (promoting menstruation), and insufficient human safety data for these populations.
7.7 High-Dose Animal Toxicity
The median lethal dose (LD50) values of N. sativa seed volatile oil, fixed oil, and aqueous extract in male Swiss albino mice were determined. Intraperitoneal administration of volatile oil, aqueous extract, and fixed oil of N. sativa has LD50 values of 1,853, 3,020, and 3,371 mg/kg, respectively. These animal data indicate low acute toxicity at doses far exceeding those reported in human use, though such data cannot be directly extrapolated to humans.
8. Body Systems and Health Areas Associated with Nigella sativa
- Metabolic/Endocrine: Glycaemic control (type 2 diabetes, prediabetes), lipid profiles, body weight
- Cardiovascular: Blood pressure, atherogenic indices, heart rate
- Hepatic: Liver enzyme normalisation, NAFLD/NASH, hepatoprotection
- Renal: Creatinine, urinary protein, GFR in diabetic nephropathy
- Respiratory: Asthma (airflow limitation, FeNO, exacerbations), COPD (lung function), allergic rhinitis
- Immunological: Immunomodulation, inflammatory marker reduction (CRP, ESR, WBC)
- Dermatological: Acne vulgaris (topical), eczema
- Neurological/Cognitive: Cognition, mood, anxiety (preliminary human data)
- Antimicrobial: Antibacterial, antifungal, antiviral (primarily preclinical)
- Oncological: Anti-tumour activity (preclinical only)
N. sativa has a variety of potential effects on different indicators in clinical practice, including blood glucose, inflammatory markers, oxidative stress factors, serum lipids, blood pressure, liver and kidney parameters, and even asthma indicators. The therapeutic effects suggest that N. sativa has beneficial effects in various diseases and may be a promising complementary and alternative therapy. However, there are certain limitations in reporting and methodological quality, and future studies should improve the administration process. The clinical efficacy of N. sativa needs to be confirmed in high-quality, large-sample RCTs to generate more evidence-based clinical practice.
References
Go back