According to a Japanese research 1, eating oranges - and other citrus fruits - every day might cut the risk of cancer of all sorts by 15% to 20%. The relative risk decrease for pancreatic and prostate cancers would be roughly 37%. Citrus fruits (orange, tangerine, lemon, lime, grapefruit, etc.) had a substantial protective effect only in those who also drank green tea on a daily basis. The researchers monitored a cohort of 42,470 persons who were enrolled in a public health insurance plan for nine years. At the outset of the trial, all of the participants, who ranged in age from 40 to 79, were in good health. The findings show that the amount of citrus ingested has a direct relationship with cancer prevention: participants who ate it every day had higher protection than those who ate it just 3 or 4 times a week. Furthermore, the researchers found no evidence of a cancer-preventive benefit for green tea that was not accompanied by a regular intake of citrus fruits. "Various components of citrus fruits and green tea have a complementing function, which might explain the preventative benefit reported in this study," says Wen-Qing Li, the study's primary investigator. A questionnaire about the participants' eating habits was used to determine their citrus consumption (40 foods and drinks). The authors of the study then examined the information based on the number of cancer cases detected throughout the research.