The U.S. News & World Report released its annual assessment of the year’s best diets and, for the third consecutive year, stated that the Mediterranean diet remains the number-one best diet overall. However, the Nutrition Coalition, a group that aims to bring rigorous science to nutrition policy, said the story favors approaches based on weak science.

The Mediterranean diet focuses on eating less red meat, sugar and saturated fat while incorporating more produce, nuts and whole grains into a dietary regimen. The DASH (Dietary Approaches to Stop Hypertension) diet, which aims to prevent and lower hypertension, landed at number two, tying with the Flexitarian diet, which was ranked number three last year. The Flexitarian diet emphasizes fruits, vegetables, whole grains and plant-based protein.

“Once again, U.S. News & World Report’s annual 'Best Diets' cover story favors approaches based on weak science while rejecting others backed by far more rigorous evidence. U.S. News’ top-ranked diets, DASH and Mediterranean, are supported by little evidence proving their benefit to the American public,” Nutrition Coalition executive director Nina Teicholz said.

In fact, the second-ranked DASH diet has only been tested on about 2,000 subjects, nearly all of whom were hypertensive middle-aged adults (a population that cannot be generalized to all Americans), and in experiments lasting no longer than six months, the Nutrition Coalition noted.

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Meanwhile, data on the Mediterranean diet is backed by only “uncertain” evidence that it can prevent heart disease, according to a large and comprehensive review on the diet conducted just last year by the Cochrane Group, which specializes in systematic reviews. Another 2019 comprehensive review of the diet found that it had “no effect” on cardiovascular or all-cause mortality, the Nutrition Coalition said.

“It’s something of a mystery why U.S. News continues to promote these same diets despite multiple articles and review papers pointing out the lack of evidence for such choices,” the coalition stated.

Teicholz, who wrote about the magazine’s non-evidence-based “Best Diets” choices last year in an op-ed for the L.A. Times, added, “The magazine seems unable to respond to the evolving science.”

“The DASH and Mediterranean diets may be popular, but they are simply not backed by the kind of rigorous evidence that could give the general public confidence,” Teicholz said. “The DASH diet may be helpful for middle-aged people with hypertension eating high-salt diets, yet there are no long-term trials to show that this diet is safe in the long run, and the Mediterranean diet simply hasn’t panned out, in clinical trials, to demonstrate the kind of benefits researchers had hoped for. The biggest trial on this diet, called PREDIMED, conducted in Spain, showed a mere 0.2% benefit in cardiovascular outcomes for the intervention group compared to the control group.”

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Meanwhile, U.S. News continues to give low rankings to low-carb diets despite nearly 100 clinical trials on this type of diet, including several that lasted one year or longer, and altogether show superior results for blood glucose control and reduction in most cardiovascular risk factors, including blood pressure, as recently acknowledged by the American Diabetes Assn. Moreover, it is the only diet, other than a starvation liquid regime, that has been demonstrated in a long-term experiment to reverse the diagnosis of type 2 diabetes, the coalition noted.

“It’s clear that U.S. News continues to recapitulate unreliable dietary advice that is not supported by strong evidence. With the rates of diet-driven chronic disease persisting at record highs, it is imperative that nutrition leaders begin to adequately -- and honestly -- consider the latest and strongest scientific evidence available. Otherwise, the public will only continue to be confused by outdated, weak science that will do little to nothing to improve their health,” Teicholz said.

To determine the rankings, U.S. News said it convened an expert panel of the country's top nutritionists, dietary consultants and physicians specializing in diabetes, heart health and weight loss. Through an in-depth survey, 25 panelists scored 35 diets in seven areas, including ease of compliance, likelihood of losing significant weight in the short and long term and effectiveness against cardiovascular disease and diabetes.