Eat less red meat — bad advice?

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 tiny and only observed in large populations, the scientists said — not enough to tell individuals to change their meateating habits.

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

The studies are among the largest nutrition evaluations ever attempted and may influence future dietary recommendations. In many ways, they raise uncomfortable questions about dietary advice and nutritional research, and what sort of standards these studies should be held to.

Already they have been met with fierce criticism by health researchers. The American Heart Association, the American Cancer Society, the Harvard T.H. Chan School of Public Health and other groups have savaged the findings and the journal that published it.

Some called for the journal’s editors to delay publication altogether. In a statement, scientists at Harvard warned that the conclusions “harm the credibility of nutrition science and erode public trust in scientific research.”

The notion that Americans might not worry about how much red meat they eat is one of the more jarring in a series of dietary reversals over the years, involving salt, butter, fats, carbohydrates and more. And while the conclusion is likely to please proponents of popular high-protein diets, it seems certain to add to public consternation over dietary advice that seems to change every few years.

The average American eats about 4 ½ servings of red meat a week, according to the Centers for Disease Control and Prevention. Some 10% of the population eats at least two servings a day.