Bottom Line: Ellagic acid is found in many foods that are part of a healthy diet, but there is no evidence to support its use for cancer treatment.
Ellagic acid is a naturally occurring compound called a tannin. It can be isolated from foods such as red raspberries, strawberries, and walnuts, and has been studied in the laboratory, but not in humans. In laboratory animals, ellagic acid showed cancer-preventive properties. For example, rats fed ellagic acid before and during exposure to carcinogens (cancer-causing substances) developed fewer liver tumors than rats fed a normal diet. Similar results were shown in mice with lung or esophageal cancer. Scientists think that ellagic acid exerts these effects in two ways. First, ellagic acid enhances the activity of certain detoxification enzymes in the liver, speeding up the removal of dangerous substances from the body, while it also inhibits the cytochrome P450 liver enzymes and may prevent them from metabolizing carcinogens into more dangerous forms. Second, ellagic acid causes changes in the cell cycle of cancer cells in the test tube, leading to cell death. However, neither of these promising effects have been shown to occur in the human body.