Even Moderate Caloric Restriction Lowers Cancer Risk In Mice

That’s good news, says Dr. Mai, since this moderate caloric restriction and/or the use of a diet in which fat came from olive oil are more likely to be followed by humans and have been shown to have broad health benefits even beyond an effect on gastrointestinal cancer risk. The findings are more troubling, he adds, when you think about the continuing trend of high caloric food intake observed in most developed nations. How much is too much? Working with a well-proven mouse model of intestinal cancer, the NCI researchers allowed some mice to eat as much food as they wanted. As mice will, they ate almost all the time, with weight gain to show for it. The researchers measured the mice’s food intake and limited similar mice to only 60 percent of the amount. This satisfied all their nutritional requirements and provided a goodly amount of food to eat as well. The result: the number of the precancerous polyps also went down by 60 percent compared to the mice eating as much as they wanted.

Previous mouse studies, like epidemiological studies of humans, have shown that what gets eaten also has an effect on colorectal cancers. So Dr. Mai and his colleagues at NCI compared the number of polyps in mice on a high fat diet, mice on a “healthy” diet with olive oil and fruit and vegetable extract, and mice on the standard laboratory mouse diet. Mice consuming a diet high on fruits and vegetables had 33 percent fewer polyps than the control mice, whereas the mice on the high fat diet had slightly elevated polyp numbers.

The researchers also looked at exercise. A moderate amount of exercise did lower the number of polyps but the difference was not statistically significant. Dr. Mai is a Cancer Prevention Fellow in the Nutritional Epidemiology Branch of the NCI. He says the research team, headed by Dr. Steve Hursting, is planning to look at different combinations of caloric intake, fat, and exercise in an effort to determine effective intervention combinations that have the potential to be tested in humans.