A new study published in Science Translational Medicine suggests that fasting may help refine the action of chemotherapy on cancer cells and make it more effective, reports Scientific American's Katherine Harmon. The researchers found that mice given water but no food for two days prior to chemotherapy experienced more tumor shrinkage than mice who were allowed to eat. In certain cancers, Harmon says, the combination of fasting and chemotherapy completely obliterated the tumor. And in mice with metastases, the addition of fasting to treatment reduced metastases 40 percent more than in mice who had been fed, she adds. The fasting mice also lived longer. "Fasting appears to protect normal cells from chemotherapy's toxic effects by rerouting energy from growing and reproducing to internal maintenance," Harmon says. "But cancer cells do not undergo this switch to self-repair and so continue to be susceptible to drug-induced damage — making for what the researchers call a differential stress resistance. Fasting, then, the authors wrote, should enhance the power of chemotherapies without having to resort to 'the more typical strategy of increasing the toxicity of drugs.'"
However, the researchers note that fasting for two or three days in mice would translate to about four or five days in humans, which would also have myriad effects on the body. In addition, as cancer patients often lose a substantial amount of weight during treatment, going days without food could be dangerous, Harmon says. The team is planning a second study to see if the combination of fasting and chemotherapy can be optimized to human needs, she adds.