Lima beans are not recommended for breast cancer
Lima beans, also known as butter beans, are the seeds of the legume Phaseolus lunatus. Lima beans have relatively high levels of iron, potassium, molybdenum and fiber, and also serve as a dietary source of some B vitamins, manganese, copper and zinc. Lima beans have been shown to have antioxidant, antimicrobial, antifungal, antibacterial and hypoglycemic actions, as well as improving cholesterol levels.
Breast cancer-related effects of eating lima beans
Extracts of lima beans have been found to increase proliferation of estrogen and progesterone responsive (ER+/PR+) human breast cancer cells. In and of itself, this is not strong evidence that lima bean consumption increases breast cancer risk, however it is a troubling result that requires further study and clarification. In the mean time, we advise against consuming lima beans.
Additional comments
Lima beans should not be consumed raw and caution is advised when eating the beans overseas since lima beans contain cyanide compounds. The cyanide is released as gas when the beans are cooked, rendering the beans safe to eat. In the U.S., commercially grown varieties of lima beans are restricted to those with very low levels of cyanide compounds, while lima beans in some other countries may have much higher levels. One of lima bean's cyanide compounds is amygdalin, the basis for laetrile (see almonds for a discussion of laetrile). Consuming foods that contain cyanide (such as raw or undercooked lima beans) in combination with laetrile treatment can increase the possibility of cyanide poisoning.
Succotash, a traditional Native American dish, is a combination of lima beans and corn.
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.