Redefined ‘High-Quality’ Diet Lowers Risk of All-Cause Mortality: PURE

MUNICH, Germany—A diet that cuts back on carbohydrates and increases fat and protein proportions—a change that reflects a more balanced diet, according to investigators—is associated with a significant reduction in all-cause mortality, as well as a reduction in MI, according to a new study presented today during the late-breaking clinical trial session at the European Society of Cardiology (ESC) Congress 2018.

Based on the data from the global Prospective Urban Rural Epidemiology (PURE) study, individuals with the highest-quality diet, which included roughly 54% of energy from carbohydrates, 28% from fat, and 18% from protein, had a 25% lower risk of all-cause mortality when compared with individuals with a poorer-quality diet.

“The current dietary recommendations are based largely on data from studies conducted two to three decades ago in predominantly high-income countries,” said Andrew Mente, PhD (McMaster University, Hamilton, Canada). “In these countries, the major problem is overnutrition, or nutrient abundance, whereas in other parts of the world there is nutrient inadequacy. The recommendations we’ve come up with in high-income countries may not be applicable to other parts of the world. This is where PURE comes in and helps to characterize a diet that would be applicable globally.”

Mente said there is widespread consensus that fruits and vegetables are protective, but that recent studies from South America, the Middle East, Africa, and South Asia have shown that moderate intakes of whole-fat dairy, unprocessed meat, fish, and nuts can provide benefits. Data have also shown that a diet high in starch is harmful, he said.

PURE Investigators Shaking Things Up, Again

Last year at the ESC, the PURE investigators presented provocative data showing that diets filled with carbohydrates—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 were associated with a 23% lower risk of death.  

Continuing their nutritional research, the investigators developed a healthy-diet score based on data from 138,527 subjects from 18 countries in the PURE study. The score was derived from an analysis showing certain foods—vegetables, fruits, legumes, nuts, fish, dairy, and unprocessed red meat—were associated with a lower risk of mortality. Based on intake of these protective foods, patients received a total score on the quality of their diet, and scores were stratified by quintiles.

Individuals with an “unhealthy” diet, those in quintile 1 of the score, consumed 1.8 servings of fruit and vegetables, 0.7 servings of nuts and legumes, 0.6 servings of dairy, 0.3 servings of red meat, and 0.2 servings of fish daily. This translated into roughly 70% of their daily caloric intake from carbohydrates, 18.5% from fat, and 12% from protein. In contrast, individuals with a healthy diet, those in the highest quintile, consumed 8.4 servings of fruits and vegetables, 2.5 servings of nuts and legumes, 3.0 servings of dairy, 1.4 servings of red meat, and 0.3 servings of fish per day.

Individuals with the highest-quality diet had a 25% lower risk of death when compared with individuals with the lowest-quality diet. There was a graded, inverse association for all-cause mortality with dietary quality. There was no significant association between dietary quality and risk of major cardiovascular disease, however.

Next, using data from the ON-TARGET study, which included 31,546 individuals with vascular disease, those with the highest-quality diet had a 24% lower risk of all-cause mortality compared with those in the lowest-quintile of dietary scores. Again, there was no association with cardiovascular disease and dietary quality. However, using data from INTERHEART and INTERSTROKE, investigators did observe a 22% lower risk of MI and a 25% lower risk of stroke among individuals with the highest dietary score compared with those with the lowest-quality diet.

Eva Prescott, MD, DMSc (University of Copenhagen, Denmark), the scheduled discussant during the session, questioned the lack of association between high-quality diet and the risk of cardiovascular disease in the PURE and ON-TARGET studies. In PREDIMED, for example, adherence to a Mediterranean diet reduced the risk of major cardiovascular events compared with a traditional low-fat diet but did not reduce the risk of mortality.

“The diet score seems mainly to predict all-cause and noncardiovascular disease mortality, and there is some uncertainty of whether the PURE diet-quality score captures the many facets of diet,” said Prescott. In addition, she questioned whether it is possible for individuals to achieve a high-quality diet score—and to consume foods from all the available categories—without exceeding the recommended daily caloric intake.

Need Longer Follow-up for Cancer Data

To TCTMD, Mente said the dietary score developed from a global health study can help better inform recommendations around the world, not just in North America or Europe. Moreover, from a macronutrient perspective, a high-quality diet lines up with current dietary recommendations, the exception being the consumption of high-fat dairy and red meat. A high-quality diet based on PURE does not include “outrageous” amounts of red meat, he added, given that those with the lowest risk of all-cause mortality consumed 1.4 servings of red meat per day.

“It’s generally a more balanced diet, with moderate amounts of carbohydrates, fats, and proteins,” said Mente. “Some elements of the PURE healthy diet score, such as dairy and meat, differs from earlier advice derived from earlier studies,” but this reflects a more global approach to a healthy diet, he added. 

The American Heart Association (AHA) currently recommends limiting saturated fat to no more than 6% of daily total calories. It also recommends limiting red meat and keeping selections to lean cuts. Per day, the AHA advises having no more than 5.5 ounces (1 serving is approximately 3.0 ounces) of red meat, fish, or poultry.

Studies have differentiated between the risks of processed versus unprocessed red meat, she noted, with only higher consumption of processed red meat shown to increase the risk of coronary heart disease.

In 2015, the World Health Organization (WHO) shook up the field of nutritional research when they stated that processed red meat was carcinogenic to humans and “probably” caused cancer. Mente said the jury is still out on the cancer risks, as well on the WHO report, which was based on epidemiologic evidence. The association needs further study, he said.

“In PURE, because we have cancer events, we do see a protective effect, but for the time being we don’t have high statistical power to draw definitive conclusions,” Mente told TCTMD. “Cancer is a rare outcome and you really need to follow up for a long time. We have follow-up for 8 years and we need to go at least twice as long.

In other research presented at ESC, researchers showed that a low-carbohydrate diet, which is popular for weight loss, increased the risk of all-cause, cardiovascular, cerebrovascular, and cancer mortality. The analysis, which included 24,825 NHANES participants, found that those with the lowest consumption of carbohydrates (quintile 4) had a 32% increased risk of all-cause mortality and a 51% increased risk of coronary heart disease death compared with those with the highest consumption of carbohydrates (quintile 1).