Black seed oil lowers blood pressure

In randomized trials, black seed (Nigella sativa) taken for weeks to months lowered blood pressure modestly compared with placebo. Two reviews pooling the trials each put the fall at about 3 mmHg for systolic pressure (the top number) and a little under 3 mmHg for diastolic pressure (the bottom number). The trials disagreed widely on the size of the effect, and the largest review rated its confidence in the blood pressure results as low for systolic and very low for diastolic. The pooled trials mixed black seed oil with seed powder, capsules and extracts at many different doses.

The one oil trial here in people with high blood pressure enrolled 55 adults who stayed on their usual medicines; systolic pressure fell further over eight weeks with 5 mL of black seed oil a day than with sunflower oil. No trial identified in these sources tested black seed oil in place of blood pressure medicine. A US government summary of supplements for high blood pressure does not list black seed and states that no dietary supplement has been shown to have effects comparable to the drugs used to treat it. In rats with raised blood pressure, black seed given with the blood pressure drug losartan lowered pressure further than losartan alone.

The largest review (Jafari 2025) pooled 82 trials published from 2008 to 2024 in 5,026 people, lasting 1 to 48 weeks at 200 to 4,600 mg a day. Its blood pressure analysis covered 888 people given black seed and 769 controls, and it reported the result on a standardized scale rather than in mmHg: 0.47 lower for systolic and 0.40 lower for diastolic. Systolic pressure was lower at doses both below and above 2,000 mg a day, while diastolic pressure was lower only below 2,000 mg a day. An earlier review (Kavyani 2023), searching to August 2022, found systolic pressure 3.06 mmHg lower and diastolic 2.69 mmHg lower, with the trials differing from one another far more than chance would explain (heterogeneity 85 percent and 97 percent). The earliest review cited here (Sahebkar 2016) pooled 11 trials in 860 people with and without high blood pressure, lasting about eight weeks on average, and found that systolic pressure fell 3.26 mmHg more and diastolic 2.80 mmHg more with black seed than in the comparison groups. In that review the fall was larger in trials of seed powder than in trials of oil, and its authors state their conclusion for the powder; a separate analysis in the same review found no link between the type of black seed used and the size of the systolic fall. The published abstracts of the two later reviews do not report results by form.

In the oil trial (Shoaei-Hagh 2021), adults with high blood pressure took 2.5 mL of black seed oil or sunflower oil twice a day for eight weeks alongside their usual medicines. Systolic pressure fell more with black seed oil than with sunflower oil, and diastolic pressure, total and LDL cholesterol and fasting blood sugar also fell; the abstract does not give the size of the blood pressure difference in mmHg. No kidney, liver or patient-reported side effects were recorded.

A US government liver safety record (LiverTox) found no reports of liver injury from black seed products and describes side effects in trials as uncommon and usually mild: stomach discomfort, bloating, altered taste, diarrhea and headache, with rare rash and allergic reactions. The same record describes the blood pressure effect of black seed extracts in trials as modest and the overall evidence of clinical benefit as not very convincing, and notes that black seed is not approved by the FDA to treat any condition. In the rat study, blood levels of losartan were higher when black seed was added, though not significantly, and its authors suggest the two may interact.

The trials ran for weeks to months rather than years and measured blood pressure readings, not heart attacks or strokes. They mixed healthy adults, people with metabolic conditions and people with high blood pressure, and used many different preparations and doses.