Grapefruit contains an abundance of phytochemicals with biological activity, including various flavonoids, carotenoids, and coumarins. Naringenin is the predominant flavonoid in grapefruit and is often considered the major bioactive compound.[1] Compounds in grapefruit have been linked to various health-promoting effects, including antioxidant, anticancer, antimicrobial, anti-obesity, and antidiabetic properties.[2][3][4]
Naringenin and a few other compounds in grapefruit activate the enzyme AMPK. AMPK helps regulate metabolism, and its activation increases the breakdown of glucose and fats and decreases their synthesis.[5][6] This may be a driver of the antidiabetic, lipid-modulating, and weight-lowering effects of grapefruit. However, fiber and other nutritional compounds in grapefruit likely also play a role.[6]
Grapefruit may lower blood pressure by promoting the dilation of blood vessels possibly by increasing the synthesis of nitric oxide.[7][6]