Black seed contains many bioactive phytochemicals that likely contribute to its effects, but thymoquinone is considered its main active compound. Further, its content of polyunsaturated fatty acids, vitamins, minerals, and soluble fiber may have positive biological effects. Regardless, our current understanding of how black seed works is largely theoretical and based on animal and in vitro research.
Black seed may modulate lipid levels by several possible mechanisms, including reduced cholesterol synthesis (via downregulation of the rate-limiting enzyme HMG-CoA reductase), increased clearance of low-density lipoprotein (LDL) cholesterol from the blood, and increased synthesis of bile acids.[1]
Improved glycemic control may be due to reduced intestinal absorption of glucose (via inhibition of the sodium-glucose cotransporter), reduced synthesis of glucose by the liver, and improved integrity of pancreatic beta cells (insulin-secreting cells).[1]
Black seed also appears to activate AMPK in skeletal muscle and liver cells, which likely explains some of its antidiabetic and lipid-lowering properties.[2]
The anti-inflammatory and antioxidant effects of black seed may occur for several reasons, most likely through increasing the levels of antioxidant enzymes, reducing lipid peroxidation, inhibiting NF-KB activity, and reducing the formation of various inflammatory mediators.[3][4]