Grapefruit Compound Kills 92% of Lung Cancer Cells and Reduces Risk in Humans: Naringenin, a flavonoid found abundantly in grapefruit, was shown in this new study to kill up to 92% of human lung cancer cells (A549) by vastly increasing the production of damaging free radicals in the cancer cells. Naringenin is a powerful compound with a broad range of health benefits: it’s been shown in lab studies to kill breast cancer, colon cancer, prostate cancer and leukemia cells. It also stimulates DNA repair processes in cells, and in mice has been shown to improve brain function and—incredibly—to reduce arterial plaque build-up by 41%. Grapefruit are by far the richest dietary source of naringenin, with up to 53 mg of naringenin per 100g of fruit (pink and red varieties have slightly more than white). And in one study, “frequent consumers” of grapefruit had 50% less lung cancer risk. Oranges deliver about 10 to 15 mg per 100 grams, while lemons and limes have 2 to 3 mg. However, some exotic fruits are also very good sources: kumquats (57 mg), tangelo (42 mg), sour orange, pummelo and yuzu (25 mg)—all per 100 grams. Note that commercial juices contain less than half the naringenin as the fresh fruit. While naringenin appears to have many health benefits, keep in mind that it can also strongly affect the absorption of certain medications, so ask your doctor before consuming any naringenin-rich foods!