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 (hesperidin, tangeretin, naringenin, nobiletin, quercetin) 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.
Citrus peel products and extracts 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 Orange Chicken), orange peel extract, and citrus oil. Tangeretin has been shown to interfere with the effectiveness of tamoxifen treatment.
Hesperidin, a flavanone found in oranges, tangerines, kumquats, lemons, limes and grapefruit, has the potential to interfere with cyclophosphamide 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). Alkylating agents strongly promote oxidation, leading to the concern that antioxidants (which, by definition, inhibit oxidation) might prevent alkylating agents from working properly. Hesperidin is found most abundantly in the peel, pith and membranous parts of oranges and other citrus fruits. Similar to tangeretin, food sources include orange tea, unfiltered orange juice, orange marmalade, and dishes that incorporate citrus peel such as Szechuan Orange Chicken.
Below are links to recent studies concerning this food. For a more complete list, including less recent studies, please click on oranges.