SAN DIEGO — A trip to almost any bookstore or a cruise around the Internet might leave the impression that avoiding cancer is mostly a matter of watching what you eat. One source after another promotes the protective powers of “superfoods,” rich in antioxidants and other phytochemicals, or advises readers to emulate the diets of Chinese peasants or Paleolithic cave dwellers.

But there is a yawning divide between this nutritional folklore and science. During the last two decades the connection between the foods we eat and the cellular anarchy called cancer has been unraveling string by string.

This month at the annual meeting of the American Association for Cancer Research, a mammoth event that drew more than 18,500 researchers and other professionals here, the latest results about diet and cancer were relegated to a single poster session and a few scattered presentations. There were new hints that coffee may lower the risk of some cancers and more about the possible benefits of vitamin D. Beyond that there wasn’t much to say.

In the opening plenary session, Dr. Walter C. Willett, a Harvard epidemiologist who has spent many years studying cancer and nutrition, sounded almost rueful as he gave a status report. Whatever is true for other diseases, when it comes to cancer there was little evidence that fruits and vegetables are protective or that fatty foods are bad.