Lima beans, also known as butter beans, are the seeds of the legume Phaseolus lunatus or Phaseolus limensis. Lima beans have relatively high levels of copper, iron, thiamin (vitamin B1) and fiber. Lima beans have been shown to have antioxidant, antimicrobial, antifungal, antibacterial and hypoglycemic actions, as well as improving cholesterol levels. Lima beans should not be consumed raw since raw lima beans contain cyanide compounds. The cyanide is released as gas when the beans are cooked, rendering the beans safe to eat.
Breast cancer-related effects of eating lima beans
A peptide isolated from the large lima bean (P. limensis) has been found to have antiproliferative activity in human liver cancer and neuroblastoma (nerve cancer) cells. Lima bean lectin has been reported to inhibit angiogenesis, but we have found no studies since 2005 on this topic. In fact, copper has been shown to promote angiogenesis in existing cancers and lima beans have a relatively high copper content.
Lima bean compounds have been shown have angiotensin converting enzyme inhibitory activity, in other words, to act as ACE inhibitors. Use of ACE inhibitors (to treat hypertension or heart failure) has found to be associated with an increased risk of breast cancer recurrence, however this is very thin evidence regarding lima beans that should be studied more thoroughly. 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 result that requires further study and clarification. In the mean time, dry beans (Phaseolus vulgaris), which have well-established anti-cancer properties, are a better choice than lima beans.
The high copper content of lima beans means they should be avoided by women with inflammatory breast cancer (IBC).
As note above, lima beans should not be consumed raw. Caution is also advised when eating these beans overseas. 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.
Below are links to recent studies concerning this food. For a more complete list of studies, please click on lima beans.