Studies have not established the effect of potatoes on breast cancer
By "potatoes" we mean white potatoes; sweet potatoes and yams are covered in another webpage. Consuming whole cooked potatoes with the peel has been shown to improve the cholesterol profile of laboratory rats. Potatoes are a good dietary source of vitamin C, potassium, magnesium and zinc. Compounds with known cancer-fighting properties found in potatoes include glycoalkaloids such as α-chaconine and α-solanine, as well as gallic acid. Potato extracts have been shown to suppress proliferation and induce apoptosis of human lymphoma, liver, stomach, cervical, colon, and prostate cancer cells. One study found that overall mortality in older Dutch women was lower for women following a "healthy" modified traditional Dutch diet: the traditional diet was made healthier by reducing alcohol and meat consumption and increasing vegetable intake without eliminating potatoes (however note that most of the potatoes would have been boiled or steamed, rather than fried). Potato consumption has been found to be associated with increased risks of oral and rectal cancer. Intakes of pan fried potatoes and French fried potatoes have also been found to be associated with higher risks of oral, laryngeal and esophageal cancers.
Breast cancer-related effects of eating potatoes
Potato extract has been shown to suppress proliferation of mouse mammary carcinoma cells. Fried potatoes were found in one study to be associated with increased risk of ER- breast cancer. Various "meat and potatoes" dietary patterns have been found to be associated with increased risks of many cancer types, including breast cancer. However, it is possible that these heightened risks may be due primarily to red meat and fried potato consumption. A 2011 study found a link between increased starch intake after a diagnosis of early-stage breast cancer and a greater risk of recurrence.
Additional comments
Potatoes typically are grown using a great deal of pesticides and significant levels of pesticides are typically present in potatoes whether purchased raw or in precooked forms such as hash browns or French fries. Studies have found increased mortality from hormone-dependent cancers in traditional potato-growing areas, presumably from potato pesticide exposure. Peeling potatoes reduces but does not eliminate pesticide exposure from the cooked food and it eliminates the vitamin D and other beneficial nutrients found primarily in the skin. Potatoes with red skins incorporate anthocyanidins that are know to be provide some protection against breast cancer risk. We would suggest buying red-skinned organic potatoes and eating them (along with their skins) after steaming or boiling them.
Acrylamide, a chemical contained in potato chips and French fries, among other foods, was initially suspected to be a potent carcinogen. However, acrylamide intake within the range of U.S. diets has not been found to be associated with increased risk of breast cancer, nor does it appear to increase the risks of other cancer types.
The potato components alpha-chaconine and alpha-solanine both have been found to inhibit the growth of normal human liver cells in addition to inducing apoptosis of liver cancer cells. Medicinal potato extracts containing these compounds are to be avoided.
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.