Effects of Nigella sativa seeds (black cumin) on insulin secretion and lipid profile: A pilot study in healthy volunteers

It has been claimed that Nigella sativa seeds (NSS), also known as black cumin, have antidiabetic and lipid-lowering properties. Our pilot study investigated the effects of powdered NSS on insulin secretion and lipid profile in healthy male volunteers. We conducted a double-blind, randomized, placebo-controlled 4-week trial in 30 subjects, receiving NSS powder (1 g/day) or placebo orally (15 subjects/group). Insulin secretion as determined by the hyperglycaemic clamp technique, insulin sensitivity as well as cholesterol and triglycerides serum concentrations, were measured before and after treatment. NSS powder administration was clinically well tolerated. It did not modify fasting glycaemia and insulinaemia, and was ineffective on glucose-induced insulin secretion and insulin sensitivity. No significant changes on serum lipids were observed after treatment in any treatment groups, nor between the two treatment groups. However, in the treated group only, there was a significant correlation between total cholesterol change after treatment and its baseline level (r = -0.71, P = 0.006, n = 13), and between low-density lipoprotein (LDL) cholesterol change after treatment and its baseline level (r = -0.74, P = 0.004, n = 13). No such correlations were found for high-density lipoprotein (HDL) cholesterol, and for triglycerides. These results do not confirm any NSS effect on glucose regulation; however, they suggest that NSS powder may be of interest in lowering lipid concentrations in hyperlipidaemic subjects.