Two studies shed new light on the link between diet and cancer, bolstering evidence that red meat may raise colorectal cancer risks but casting doubt on whether fruits and vegetables can help prevent breast cancer.

The research doesn’t settle the questions, partly because both studies asked about eating habits only in adulthood. Some researchers think that may have less impact on cancer risk than lifelong eating habits.

Breast cancer risk, especially, may be more dependent on a woman’s diet during adolescence, when breast cells are rapidly dividing and are more vulnerable.

Still, both studies are consistent with evolving thinking about specific foods and their influence on cancer risks. The studies are published in today’s Journal of the American Medical Association.

In numerous other studies examining diet and cancer, the relationship between meat consumption and colorectal cancer is the among the strongest, with most finding that eating lots of red meat and processed meats increases the risk.

Even if they don’t help prevent breast cancer, fruits and vegetables, as well as limiting red meat intake, are good for the heart, said Dr. Walter Willett, a Harvard University nutrition expert and author of a book promoting those habits.