The red-wine compound resveratrol has received a lot of attention as a possible therapy to prevent heart disease and cancer with few side effects in patients at high risk for the diseases. Now a new study reports that resveratrol protects against colorectal cancer in mice, but more so at low, not high, doses (Sci. Transl. Med. 2015, DOI: 10.1126/scitranslmed.aaa7619). Karen Brown of the University of Leicester, in England, and colleagues studied mice with genetic mutations that made them susceptible to developing adenomas in their intestines. Compared with animals not receiving resveratrol, those getting a high dose had a 25% smaller total tumor volume, while the mice receiving a low dose had a 52% smaller volume. But the researchers observed this pronounced low-dose effect only in mice that ate a high-fat diet for reasons that the team doesn’t fully understand. The findings, Brown says, suggest that resveratrol’s effects don’t increase linearly with dosage.