Kaluduru (Nigella sativa): Black Seed and the 82-Trial Verdict

Kaluduru (Nigella sativa) arrived in Sri Lanka along the spice routes and settled into two places at once: the curry-powder tin and the medicine cupboard. The tiny black seeds — called kalonji in India and habbat al-barakah, "the blessed seed", across the Arab world — carry a reputation for curing "everything but death". By 2025, researchers had assembled 82 randomised trials to test how much of that reputation survives contact with data. Quite a lot of it does.

Botanical and Cultural Background

Nigella is a small annual of the buttercup family with feathery leaves and pale blue flowers; its seed capsules split to release matte-black, sharp-edged seeds with a faint oregano-like aroma. It is not related to true cumin (suduru) despite the shared name. The seeds are imported rather than grown in Sri Lanka, and their medicinal fame in the island owes much to Unani (Islamic) medicine, in which black seed is a foundational remedy. The active compound is thymoquinone, concentrated in the seed oil.

Traditional Uses in Sri Lankan Medicine

• Immunity and colds — a teaspoon of seeds or a few drops of oil with bee honey, especially in the wet season.
• Digestion — roasted seeds in curries and pickles as a carminative.
• Asthma and allergies — seed oil taken orally or inhaled as steam.
• Skin and hair — oil applied to eczema, and massaged into the scalp.

What the Research Shows

Black seed is now one of the best-studied herbal medicines. A 2025 GRADE-assessed meta-analysis in Pharmacological Research pooled 82 randomised trials with over 5,000 participants and found meaningful improvements in cardiovascular risk factors — lipids, blood pressure and blood glucose — across doses of 200–4,600 mg daily. A 2024 updated meta-analysis confirmed reductions in total and LDL cholesterol; another 2024 analysis found benefits in allergic rhinitis symptoms; and a 2024 meta-analysis reported improved markers of blood-vessel (endothelial) function. Thymoquinone's anti-inflammatory and antioxidant mechanisms are well characterised (Ahmad et al., 2013). Effects on blood sugar in type 2 diabetes are consistent though modest. The reputation as a cancer cure, by contrast, rests on laboratory work only.

Evidence updated September 2026.

How Kaluduru Is Prepared

The traditional dose is half to one teaspoon of seeds daily, lightly crushed and taken with bee honey or warm water, or the equivalent seed oil (about a teaspoon). Roasting the seeds briefly before grinding improves flavour for cooking; they are excellent in pickles, naan-style breads and lentil dishes. Cold-pressed oil should be kept away from light and used within months.

Safety and Precautions

Culinary amounts are safe for all. In supplement doses, black seed can add to the effect of blood-pressure, glucose-lowering and sedative medicines, so combine with care and monitoring. Avoid medicinal doses in pregnancy (the seeds have traditionally been considered to stimulate the uterus) and stop two weeks before surgery. Rare skin reactions to the oil have been reported.