PURE Investigators: Rethink Diet Guidance to Plug More Fats, Fewer Carbs

New data from the massive epidemiological study suggest higher mortality with higher carb and lower fat intake.

PURE Investigators: Rethink Diet Guidance to Plug More Fats, Fewer Carbs

BARCELONA, Spain—No strangers to controversy, PURE investigators are calling for a rethink of dietary guidelines that have promoted carbohydrates over fats, citing new data from their massive, global epidemiology study.

The findings suggest that diets high in carbs and/or low in fats are associated with a greater risk of mortality.

Guidelines, including Dietary Guidelines for Americans, recommend that adults consume 20-35% of their daily calories from fats, with saturated fatty acids limited to less than 10% of energy intake. The American Heart Association also singles out saturated fats, specifying that people wishing to lower their LDL cholesterol should reduce their intake of saturated fat to 5 or 6% of their total calories.

But according to data presented here at the European Society of Cardiology (ESC) Congress 2017 and published simultaneously in the Lancet, diets with the highest carbohydrate representation—making up, on average, 77% of daily calories—were associated with a 28% higher risk of death compared with diets where carbohydrates made up just 46% of calories. By contrast, diets with the highest fat intake (35% of daily calories) were associated with a 23% lower risk of death.

Dietary guidelines need to be reconsidered based on new evidence. Mahshid Dehghan

“Dietary guidelines need to be reconsidered based on new evidence,” lead investigator Mahshid Dehghan, PhD (Population Health Research Institute, Hamilton, Canada), said in a morning press conference. “We are saying: more relaxation of the current restriction on the fats and more emphasis on [lowering] carbohydrate when it is high.”

This analysis from the Prospective Urban Rural Epidemiology (PURE) study looked at dietary intake in 135,335 individuals aged 35-70 years from 18 countries worldwide and zeroed in on the balance of nutrients, specifically, carbohydrates and fats. Over 7.4 years of follow-up 5,796 subjects died and 4,784 had a major cardiovascular event. When carbohydrate intake was divided into quintiles, Dehghan and colleagues found that the highest carbohydrate intake (77.2% energy from carbs) was associated with the greatest increased risk of mortality, when compared with the lowest intake. By contrast, the highest quintile of fat intake (35.3% of daily calories) was associated with a significantly reduced risk of mortality, as compared with the lowest intake.

Saturated Surprise

Of note, the benefits of higher fat intake persisted regardless of the type of fat consumed. Digging into this finding following Dehghan’s main-tent presentation, session co-chair Steen Dalby Kristensen, MD, DMSc (Cardiovascular Research Centre, Aarhus University, Skejby, Denmark), said he “was a bit surprised” by the saturated fat findings, and the findings for fat more broadly. “What should we now recommend?” he asked.

According to these data, Dehghan replied, a daily saturated fat intake in the range of 10-13% of energy intake is associated with a significantly lower risk of death.

Senior investigator for PURE, Salim Yusuf, MD (McMaster University, Hamilton, Canada), was a little more colorful in his remarks, speaking to reporters following a morning press conference. He noted that nearly 40 years’ worth of nutrition guidance has painted fat as the “villain,” including—controversially—the American Heart Association.

“Study after study has refuted this, and yet, the traditional ‘church’ has stuck to the traditional way of thinking,” Yusuf said, namely that fat and saturated fat are associated with cardiovascular disease and death.

The lack of an association between fat intake of any kind and cardiovascular outcomes, and indeed the overall benefit associated with “high” fat intake (in the range of 35%) in PURE adds to an already established body of research at odds with dietary advice that has dominated cardiology for decades, he said.

“There are excellent meta-analyses of hundreds of thousands of people, before PURE, that have nothing to do with PURE, that show [fat’s] neutrality on health,” Yusuf said. Yet people with the “traditional view” (fat is bad) have dismissed or found fault with this research, rather than use it to question dietary dogma, he added. “Instead they have taken these studies and picked them apart. You can pick PURE apart, but it’s the totality of evidence that matters.”

It’s time for groups like the AHA to reconsider their stance, he continued. “I think the AHA is a big force for good, so you have to take this in its bigger context, but maybe they should convene a group of people who haven’t been involved in the previous guidelines,” Yusuf said.

Contacted for comment, the AHA put TCTMD in touch with epidemiologist Russell Luepker, MD (University of Minnesota, Minneapolis), who was reluctant to be drawn into a debate on whether the AHA nutrition guidelines need new writers.

“The low-fat diet, which has gotten much more traction in the States than in other parts of the world, may not be ideal,” Luepker conceded. The problem in the US has been that food manufacturers, which carry major political heft, in response to low-fat recommendations supplied low-fat foods comprised of low-nutrition, refined carbohydrate foods, he said. “That is not what we intended to happen, but it is what happened.”

I don’t think PURE is the last word. Salim Yusuf

But any new dietary guidelines need to be based on a plurality of studies, Luepker insisted. “I commonly say, epidemiological studies can lead us into thinking and other experiments, but to say that because of an epidemiological study like this we should change everything, I think that’s going a step too far.”

That’s a position Yusuf himself appeared to agree with, saying: “I don’t think PURE is the last word.”

New Insights, Not Final Ones

During her late-breaking presentation, and in a morning press conference, Dehghan took pains to remind her audience that most of the world’s population lives in low- or middle-income countries, yet dietary recommendations are drawn from studies in the highest income nations. As such, PURE is providing first-of-its-kind insights into what nutrients various populations around the world are eating and how these might be linked with survival.

In many low-and middle-income countries, diets consist of more than 65% of energy from carbohydrates and in Africa, South Asia, and China, for example, just 20% of energy comes from fats. In these regions, she said, dietary recommendations should focus on reducing intake of carbs instead of reducing intake of fats. In North America and Europe, however, despite guidance recommending low intake of fats, the PURE data suggest that people in these regions are striking the right mix, with fat intake hovering around 30% and saturated fat making up 11-12%.

Speaking with TCTMD, study co-author Andrew Mente, PhD (McMaster University), who separately presented other PURE findings here today looking at fruit and vegetable intake, said that in terms of saturated fat intake, North Americans and Europeans are “probably right where they want to be—and can probably even go a little higher.”

What’s needed is moderation, he continued. “We are not advocating, by any means, just eat as much fat as you want. But certainly if people are eating a lot of carbohydrates, in excess of 60% of their daily energy, then to get them down to moderate levels, which typically leads to a corresponding increase in fats that would probably be better for them.”

Of note, Dehghan said she and her colleagues have not yet looked at the role played by protein, nor have they looked at different sources of carbohydrates and fats. These, she told TCTMD, are actively being analyzed in studies she hopes will wrap up next year.

ESC 2017

Shelley Wood is the Editor-in-Chief of TCTMD and the Editorial Director at CRF. She did her undergraduate degree at McGill…

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