WEDNESDAY, Feb. 8, 2012 (HealthDay News) -- Fasting, especially when combined with chemotherapy, appears to slow the growth of cancerous tumors in mice, new research suggests.
Experts note that the results of animal studies often don't hold up when tried in humans.
However, researchers have started testing whether fasting can help human patients with breast, ovarian and urinary tract cancer.
In the mouse study, published in the current issue of Science Translational Medicine, researchers found that fasting slowed the growth of growth of breast cancer, melanoma, glioma and human neuroblastoma in mice.
In some cases, fasting was as effective as chemotherapy, according to the study.
"The combination of fasting cycles plus chemotherapy was either more or much more effective than chemo alone," senior study author Valter Longo, a professor of gerontology and biological sciences at the University of Southern California, said in a university news release.
Researchers said that normal cells deprived of nutrients during fasting enter a dormant state, whereas when studied in the lab, a type of cancer cell attempted to keep growing and dividing.
That, in turn, led to a "cascade of events" that damaged the cancer cells' DNA and led to cell death.
"A way to beat cancer cells may not be to try to find drugs that kill them specifically but to confuse them by generating extreme environments, such as fasting, that only normal cells can quickly respond to," Longo concluded.
The study authors noted that results from the initial phase of a clinical trial, which involved patients with breast, urinary tract and ovarian cancer conducted at the USC Norris Comprehensive Cancer Center, have been submitted for presentation at the annual meeting of the American Society of Cancer Oncologists. This trial tested the safety of short-term fasts two days before and one day after chemotherapy.
"We don't know whether in humans it's effective," Longo said. "It should be off limits to patients, but a patient should be able to go to their oncologist and say, 'What about fasting with chemotherapy or without' if chemotherapy was not recommended or considered?"
The researchers warned that fasting may not be safe for all cancer patients, particularly those who have already lost a significant amount of weight or have other conditions, such as diabetes. They added that fasting can cause headaches and a drop in blood pressure. The study also pointed out that cancer-free survival resulting from fasting may not extend to large tumors.
According to the American Cancer Society, "available scientific evidence does not support claims that fasting is effective for preventing or treating cancer. Even a short-term fast can have negative health effects, while fasting for a longer time could cause serious health problems."
The American Cancer Society provides more information on fasting and cancer.