Public health officials for years have urged Americans to limit consumption of red meat and processed meats because of concerns that these foods are linked to heart disease, cancer and other ills.

But on Monday, in a remarkable turnabout, an international collaboration of researchers produced a series of analyses concluding that the advice, a bedrock of almost all dietary guidelines, is not backed by good scientific evidence.

If there are health benefits from eating less beef and pork, they are small, the researchers concluded. Indeed, the advantages are so faint that they can be discerned only when looking at large populations, the scientists said, and are not sufficient to tell individuals to change their meat-eating habits.

“The certainty of evidence for these risk reductions was low to very low,” said Bradley Johnston, an epidemiologist at Dalhousie University in Canada and leader of the group publishing the new research in the Annals of Internal Medicine.