The cancer-fighting properties of citrus fruits may be due to their high flavonoid content. Flavonoids are natural compounds that lessen inflammation and protect against cell damage from free radicals, two factors believed to contribute to cancer development, explains the Cleveland Clinic. The peels of citrus fruits are particularly rich in flavonoids. In a 2013 study published in Food & Function, researchers used mice to examine the effects of citrus fruit peel extract on human prostate tumor cells. Decreases in tumor size and volume were observed in connection with the use of the extract when injected and taken orally. The study team deemed the extract, called Gold Lotion (GL), as a potentially viable anti-cancer agent in the treatment of prostate cancer.
But what about human subjects? Researchers from a 2010 longitudinal study published in the International Journal of Cancer involving more than 42,400 Japanese adults found that individuals who ate citrus on a daily basis stood at a lower risk for cancers, particularly pancreatic and prostate cancer. A reduction in overall cancer risk was particularly prominent in adults who regularly consumed citrus as well as 1 or more cups of green tea daily.