Studies have not established the effect of peanuts on breast cancer
Peanuts contain resveratrol and are an excellent source of monounsaturated fat. Consumption of peanuts is associated with lower levels of inflammatory markers, which may account for the inverse relationship between nut consumption and cardiovascular risk and diabetes risk. Peanuts have also been shown to promote weight management when consumed as part of a moderate fat diet because of its satiating effect. Frequent peanut consumption is associated with a reduced risk of gallstone disease in men. Peanut extracts have been shown to suppress the proliferation of human prostate cancer cells.
Cancer-related effects of eating peanuts
Peanuts typically are infected to some extent with molds which produce aflatoxins, which are mutagenic, carcinogenic and teratogenic and cause immuno-suppression in humans. Aflatoxin B1 has been shown to cause liver cancer, especially in hepatitis B-positive individuals. Peanuts have been shown in several studies to stimulate proliferation of colon cancer cells. However one large Taiwanese study found that peanut consumption was associated with lower colorectal cancer risk. Breathing the fumes of peanut oil used in frying has been shown to increase the risk of lung cancer. Breast cancer patients have been shown to be at higher risk for other cancers and should avoid known mutagens. In addition, it is possible to get the potential health benefits of peanuts by consuming other nuts and foods. Based on the available evidence, it makes sense to limit consumption of peanuts, peanut butter, and peanut oil.
Additional comments
Although the United States is a net exporter of peanuts, in 2007 the U.S. imported nearly $29.2 million worth of peanuts, mainly from Argentina, China and Mexico. The aflatoxin problem described in the section above is not related to the multistate outbreak of salmonella that occurred in January 2009. The outbreak was caused by salmonella-contaminated peanut butter and peanut paste produced by the Peanut Corporation of America. Peanut oil typically contains a small fraction of the aflatoxins contained in peanuts and peanut butter. Almond butter, found in health food stores and some supermarkets, can often be an acceptable substitute for peanut butter.
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.