Watermelon is recommended for breast cancer
Watermelon (Citrullus vulgaris) is a rich dietary source of vitamin C. Watermelon also is an excellent source of carotenoids such as beta-carotene, lycopene, and beta-cryptoxanthin, as well as L-citrulline (an effective precursor of L-arginine) and a small fraction of cucurbitacins, all of which have been shown to have chemopreventive properties. Watermelon also has been shown to possess anti-inflammatory and antimicrobial properties, and to reduce cardiovascular risk factors by improving glycemic control and ameliorating vascular dysfunction in laboratory animals with type 2 diabetes.
Breast cancer-related effects of eating watermelon
Consumption of the watermelon, papaya and cantaloupe (taken together) was found to be associated with a lower risk of breast cancer in one 2009 study of Chinese women. However, a previous 2003 study found no reduction in breast cancer risk associated with watermelon consumption. Cucurbitacins, compounds found in watermelon, have been shown to induce cell cycle arrest and apoptosis in human breast cancer cells. The high carotenoid levels found in watermelon are also likely to offer protection against breast cancer.
Additional comments
Watermelons should be washed before cutting to remove pesticide residue. Although watermelon seeds and watermelon rind (including pickled watermelon rind) are eaten by many peoples across the world, we have not been able to determine whether this practice is completely safe.
Colocynth (Citrullus colocynthis), also known as bitter apple or bitter cucumber, and bitter Hawkesbury watermelon (Citrullus lanatus) are closely related to watermelon, but with a much higher fraction of cucurbitacins. Colocynth and other high-cucurbitacin cucurbits are sometimes sold as herbal remedies, including for cancer. However, while chemotherapy based on cucurbitacins may eventually be developed, these are toxic chemicals whose safety profiles and appropriate dosages have not been determined.
Note that while we are continually searching for new evidence specifically concerning this food, there is not much interest in it among breast cancer researchers, so few studies are available.