How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Nigella (black cumin)
Nigella seeds or oil: slightly less weight, blood pressure, blood glucose, and cholesterol in meta-analyses, on evidence that is mostly of low quality.
Benefits
- Weight: on average 1.76 kg and 0.85 BMI points lower than under placebo, across 13 trials and 875 adults.
- Blood pressure: 3.06 mmHg lower systolic on average, and a clear drop in 70 healthy volunteers with 5 mL of oil per day for 8 weeks.
- Blood glucose: in 94 type 2 diabetics, 2 g of seeds per day for three months lower fasting blood glucose and HbA1c; same result over one year in 114 patients.
- Cholesterol: lower total cholesterol, LDL and triglycerides, higher HDL, across 34 studies and 2,278 adults.
- Non-alcoholic fatty liver: in 120 patients, three months of standardized oil reduce steatosis grade and liver enzymes (ALT, AST).
- Asthma: better control score and fewer eosinophils in 80 asthmatics, with 500 mg of oil twice daily for 4 weeks.
- Knee osteoarthritis: in 116 patients, one month of oral oil reduces pain and paracetamol consumption.
- Inflammation: CRP and TNF-α drop, across 20 trials and 1,086 adults.
Precautions
Kidneys: beyond 2000 mg per day, blood urea increased in a meta-analysis of 19 trials; creatinine also rose in adjusted analyses. Antidiabetics: taken in addition to oral antidiabetics, nigella lowered blood glucose further. Adverse effects: mild in 76 elderly hypertensives, mostly digestive (dyspepsia in 15.7%, nausea in 7.8%, constipation in 5.2%). Limitations: in 76 elderly hypertensives, the seed extract did not lower blood pressure better than placebo. Waist circumference does not drop significantly in the meta-analysis of 13 trials. An overview of 20 meta-analyses judges their quality low or critical for the most part: out of 110 results, 88 rely on very low-quality evidence. The authors call for larger, higher-quality trials, notably on fatty liver.
Recommended dosage
200 to 4600 mg per day depending on the trials; 2 g of seeds per day for blood glucose, 5 mL of oil per day for blood pressure.
How to take it
- Who it is for: most trials involve sick people (type 2 diabetes, fatty liver, asthma, osteoarthritis) or overweight individuals; only one involves blood pressure in healthy volunteers.
- Powdered seeds: 2 g per day, tested for three months and one year in type 2 diabetics, and eight weeks in patients infected with Helicobacter pylori.
- Oil: 5 mL per day for 8 weeks for blood pressure, 2.5 mL twice a day for 3 months for fatty liver.
- Oil or powder: oil lowers total cholesterol and LDL more; only powder increased HDL.
- Duration: from 1 to 48 weeks depending on the trials.
- With an antidiabetic drug: in the diabetes trials, black cumin was added to oral antidiabetic drugs.
Did you know?
An overview of 20 meta-analyses on black cumin screened 110 results: 88 are based on very low-quality evidence, and only 5 on moderate-quality evidence.
What the studies say
This meta-analysis of randomized controlled trials involving 5026 participants evaluates the effect of black cumin supplementation on cardiovascular risk factors. It shows that black cumin can significantly improve many markers related to metabolic and cardiovascular health, such as weight, blood pressure, blood glucose, and lipid profiles. The results suggest that black cumin could be a promising adjunctive therapy for these risk factors.
Jafari A, Mardani H, Faghfouri AH, Fashtali ZM, Hashemi M, Yousefabady MA, Javid R, Golabi S, Arghavan B, Musazadeh V, Naghashpour M. — Pharmacological research (2025) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more