Huge new study casts doubt on conventional wisdom about fat and carbs – STAT

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at, once a dirty word when it came to diet, has been edging back toward respectability. New results from a huge international study help continue to reshape its image while at the same time casting doubt on the wisdom of eating lots of carbohydrates and questioning the “more is better” recommendations for eating fruits and vegetables.

The latest evidence comes from data released Tuesday by the international Prospective Urban Rural Epidemiology (PURE) study. Its research team recorded the eating habits of 135,000 adults in 18 countries — including high-income, medium-income, and low-income nations — and followed the participants’ health for more than seven years on average.

Among the PURE participants, those with the highest intake of dietary fat (35 percent of daily calories) were 23 percent less likely to have died during the study period than those with the lowest fat intake (10 percent of calories). The rates of various cardiovascular diseases were essentially the same across fat intake, while strokes were less common among those with a high fat intake.

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Upending conventional wisdom, the findings for carbohydrate intake went in the opposite direction. PURE participants with the highest carbohydrate intake (77 percent of daily calories) were 28 percent more likely to have died than those with the lowest carbohydrate intake (46 percent of calories). The results were presented at the European Society of Cardiology meeting in Barcelona, and published in the Lancet.

“These results point to the fact that human biology is very similar across the globe,” said Dr. Eric Rimm, professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health. “It’s not healthy to eat highly processed carbohydrates no matter where you live.”

In a related paper, the PURE results challenged two widely held beliefs about fruits and vegetables. While most dietary guidelines stress the importance of eating more vegetables, among the PURE participants, eating more fruits, and more seeds and beans, was associated with greater benefits than eating more vegetables. Guidelines also tend to stress that if eating some fruits and vegetables is good, more must be better. But among the study participants, those whose diets included three to four servings of fruits and vegetables a day were no more likely to have died as those whose diets included eight or more servings a day.

In a nutshell, a healthy diet based on the PURE results would be rich in fruits, beans, seeds, vegetables, and fats, include dollops of whole grains, and be low in refined carbohydrates and sugars.

“One of the most important take-home messages from the PURE study is that bioactive foods that give rise to new plant life, like fruits and seeds, should be an important part of everyone’s diet,” said Dr. Dariush Mozaffarian, dean of the Tufts Friedman School of Nutrition Science and Policy.

As an observational study, PURE can’t prove cause and effect. In an effort to eliminate the biases that are common in observational studies, the researchers took blood samples from the majority of the study participants and analyzed them for cholesterol and other lipids. Participants with higher intakes of fats, or lower intakes of carbohydrates, had lower levels of low-density lipoprotein (so-called bad cholesterol) and triglycerides, and higher levels of protective high-density lipoprotein (so-called good cholesterol). Those tests help corroborate the main findings.

The PURE results provide strong support for evidence accumulating over the past decade on what makes a healthy diet, said Mozaffarian. “Cutting back on starch and sugar and adding more fat and more foods from plants, especially bioactive fruits and seeds, is where we should be headed,” he said.

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