Oranges contain substances that have been shown to be antiproliferative and antioxidant. The major antioxidant component of orange juice is vitamin C. Studies have also found that oranges inhibit breast cancer in mice and have proapoptic effects on breast cancer cells. One major 2015 study reported that people with diets high in oranges (but not orange juice) may be at slightly increased risk for malignant melanoma, possibly from ingesting photosensitizing compounds called psoralens found in citrus fruits.
Breast cancer-related effects of eating oranges
Oranges and tangerines and their peels contain flavonoids (beta-cryptoxanthin, hesperidin, naringenin, nobiletin, tangeretin) that have been shown to have antiproliferative and proapoptotic effects on breast cancer cells. Dietary flavonoids are also believed to aid the body's antioxidant defenses against free radicals. Oranges also contain limonoids, which appear to possess substantial anticancer activity.
Orange juice has been shown to reduce the extent of DNA damage caused by certain mutagens. Although initial studies concerning the chemopreventive properties of oranges are promising, they have for the most part been conducted primarily with in vitro cell culture and animal models. However, Korean and Uruguayan studies have found an association between orange juice consumption and lower incidence of breast cancer. In addition, a large U.S. prospective study reported that women with high orange intake in early adulthood had reduced risk of breast cancer in middle age and later years.
Tangeretin has been shown to interfere with the effectiveness of tamoxifen treatment. Citrus peel products and extracts, which can be concentrated sources of tangeretin, should not be used during treatment with tamoxifen. This includes orange peel and tangeretin supplements, orange flavored teas, orange marmalade, dried tangerine peel (an ingredient in many Chinese dishes such as Szechuan Orange Chicken), orange peel extract, and citrus oil.
Hesperidin, a flavanone found in oranges, tangerines, kumquats, lemons, limes and grapefruit, has the potential to interfere with cyclophosphamide and aromatase inhibitor treatment. Cyclophosphamide is an alkylating agent frequently used in combination with anthracyclines ( Adriamycin, epirubicin) and/or taxanes (Taxol, Taxotere) to treat breast cancer. Examples of chemotherapy regimens incorporating cyclophosphamide include TEC (docetaxel, epirubicin, and cyclophosphamide), TAC (taxotere, adriamycin and cyclophosphamide), and FEC (cyclophosphamide, epirubicin and 5-fluorouracil). Hesperidin is found most abundantly in the peel, pith and membranous parts of oranges and other citrus fruits. Food sources include orange tea, unfiltered orange juice, orange marmalade, and dishes that incorporate citrus peel.
Non-organic oranges should be washed thoroughly before using to prevent a transfer of pesticides and other contaminants to the flesh during cutting.
Below are links to recent studies concerning this food. For a more complete list, including less recent studies, please click on oranges.