Findings from the Prospective Urban Rural Epidemiology (PURE) Study—which consisted of more than 135,000 individuals from 18 low-, middle- and high-income countries from five continents—showed that (1) high carbohydrate intake was linked to worse total mortality, whereas high fat intake was linked to lower risk; (2) reducing saturated fat intake and replacing it with carbohydrate was linked to the most adverse effects on blood lipids; and (3) combined fruit, vegetable, and legume consumption at 3-4 servings per day were associated with a lower total mortality and non-cardiovascular mortality [1-3].

One of the most consistent dietary guidelines in the Western Hemisphere is to restrict saturated fat intake to less than 10% of total calories per day and replace saturated fat (e.g., animal fats) with unsaturated fat (e.g., vegetable oils) and complex carbohydrates [4]. However, a growing number of scientists are questioning this recommendation as more studies have demonstrated the lack of an association between fat intake and adverse health outcomes. In addition, most of the dietary recommendations are based on studies conducted in high-income countries even though most of the world’s population lives in low- or middle-income countries.

The PURE Study attempted to fill the knowledge gap by investigating the association of nutrients with mortality and cardiovascular disease (CVD) in a wide range of countries. Involving more than 200 investigators, the PURE study used country-specific food frequency questionnaires to record the habitual food intake from 135,335 adults (35-70 y/o) in 18 countries in North America, South America, Europe, Africa, Middle East, and Asia. Blood pressure was measured and fasting blood sample collected from each individual. During the follow-up, any case of death and CVD event was documented.

After a median of 7.4 years of follow-up, the study found that:

  • Higher carbohydrate intake was associated with an increased risk of total mortality, whereas intake of total fat and each type of fat was associated with lower risk of total mortality
  • Total fat and types of fat were not associated with CVD, myocardial infarction, or CVD mortality
  • High carbohydrate intake had the most adverse impact on CVD risk factors, whereas monounsaturated fats seemed to be beneficial and saturated fats were not harmful
  • Reducing saturated fats and replacing them with carbohydrates increased CVD risks
  • Increased fruit, vegetable, and legume consumption was associated with a lower risk of total mortality and non-CVD mortality. These benefits could be achieved at 3-4 servings per day (375-400 g/day). Additional consumption did not appear to further reduce risks

Even though the PURE Study is the largest study of its kind to date, the lead investigators stressed that an observational study could only draw associations. Further, the study is still ongoing, and many related questions are currently been analyzed and will be addressed in future publications.

The study results were presented at the European Society of Cardiology Congress 2017 in Barcelona, Spain, with simultaneous publications in The Lancet and in Lancet: Diabetes & Endocrinology (August 2017; in press).

Why is this Clinically Relevant?

  • Findings from this largest cohort study to date do not support the current recommendation to restrict total fat intake to less than 30% of total energy and saturated fat intake to less than 10% of total energy
  • Individuals with high carbohydrate intake, above 60% of total energy, would likely benefit from reducing carbohydrate intake and increasing fat and protein
  • In low- and middle-income countries, a typical diet may consist of more than 65% of total energy from carbohydrates. Dietary guidelines should refocus on reducing carbohydrates instead of focusing on reducing fats

Click below to read the three related publications:

The Lancet abstract

The Lancet abstract

The Lancet Diabetes & Endocrinology abstract

Reference

[1] Dehghan, M., et al., Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study. The Lancet (in press).

[2] Mente, A., et al., Association of dietary nutrients with blood lipids and blood pressure in 18 countries: a cross-sectional analysis from the PURE study. The Lancet Diabetes & Endocrinology (in press).

[3] Miller, V., et al., Fruit, vegetable, and legume intake, and cardiovascular disease and deaths in 18 countries (PURE): a prospective cohort study. The Lancet (in press).

[4] Dietary Guidelines 2015-2020. https://health.gov/dietaryguidelines/2015/guidelines/

 

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