Black seed (Nigella sativa)

The Razmpoosh meta-analysis (Phytother Res 2019) pooled 17 RCTs with 1098 participants: at 1–3 g/day of oil or powder for 6–12 weeks in patients with dyslipidaemia, black seed reduced total cholesterol by a mean 0.4 mmol/L, LDL by 0.3 mmol/L and triglycerides by 0.2 mmol/L versus placebo. The effect is smaller than with statins, methodology heterogeneous and risk of bias high. ESC/EAS 2019 and Spanish SEA 2022 recommend statins as first line in confirmed cardiovascular risk. Black seed is not in international guidelines. If the oil was bought instead of a prescribed statin, discuss with a cardiologist; substitution in proven coronary disease raises the recurrent-infarct risk.

Black seed is an over-the-counter supplement. In the Nikakhlagh RCT (Am J Otolaryngol 2011) in 66 patients with seasonal allergic rhinitis, black seed oil 0.5 mL/day for 6 weeks moderately reduced nasal congestion, itching and sneezing versus placebo. The effect was smaller than with intranasal steroids and antihistamines, the sample was small and methodology weak. No positive systematic review exists. ARIA 2020 and the Spanish SEAIC 2022 consensus recommend intranasal glucocorticoids (mometasone, fluticasone) and second-generation antihistamines (cetirizine, desloratadine) as first line in allergic rhinitis, plus allergen-contact control and immunotherapy when indicated. Black seed is not in international guidelines. If black seed oil was bought instead of the prescribed intranasal steroid, discuss with an allergist; the substitution is not justified.

Black seed is marketed as an «immune booster», especially in halal and ayurvedic shops, and intensively after the COVID-19 pandemic as «natural protection against viruses». The evidence base is weak. Reviews by Tavakkoli 2017 and later summaries describe thymoquinone effects in vitro and in animal models of influenza, asthma, and COVID-19, but few high-quality human RCTs with hard endpoints (lab-confirmed infection rates, hospitalisation, symptom duration) exist, and those are methodologically weak: small samples, varied source material, open-label designs. Cochrane has not published a systematic review on Nigella sativa for cold or flu prevention or treatment. The WHO Living Guidelines for COVID-19 (2023) and the Spanish SEIMC do not recommend black seed. Evidence-based seasonal measures are influenza and COVID-19 vaccination, hand hygiene, masking at peaks, sleep, and adequate dietary protein. If the product was bought «for immunity», consider seeking a second opinion – frequent infections, night sweats, or weight loss warrant assessment for haematological disease, HIV, or immunodeficiency rather than seed oil.

Black seed and black seed oil (Nigella sativa) are sold as a superfood and adaptogen, with promises of stronger immunity, more energy and overall wellbeing. There is no convincing evidence that it delivers these benefits in a healthy person: good-quality studies on this use have not been done. Sleep, regular movement and a varied diet support energy and resilience far more reliably than any single supplement. The seed itself, in culinary amounts, is safe.

Black seed is actively marketed as a «natural insulin alternative» and a remedy «instead of metformin». The Hadi 2021 meta-analysis (Pharmacol Res) of 16 RCTs in type 2 diabetes reported fasting glucose reductions of about 17 mg/dL and HbA1c reductions of about 0.5%. The effect resembles a weak metformin dose, but methodology limits the conclusion: trials are short (8-12 weeks), populations are heterogeneous, doses ranged from 1 to 3 g/day, and most studies kept metformin and insulin in place – so the black-seed effect is additive. RCTs with hard endpoints (micro- and macrovascular complications, mortality) have not been performed. ADA Standards of Care 2024 recommend metformin as first-line in most patients with type 2 diabetes, adding an SGLT2 inhibitor (empagliflozin, dapagliflozin) or GLP-1 receptor agonist (semaglutide, dulaglutide, liraglutide) in heart failure, chronic kidney disease, or atherosclerotic cardiovascular disease, and basal insulin at HbA1c above 10%. The Spanish redGDPS holds the same approach. Replacing metformin or insulin with black seed in type 2 diabetes worsens glycaemia and risks retinopathy, nephropathy, neuropathy, and cardiovascular events. If black seed was recommended as a substitute, consider seeking a second opinion – glycaemic targets in type 2 diabetes are reached with proven drugs.