The PURE study

Did you ever think you’d wake up to the headline “Low-fat diets could increase the risk of an early death: Major study challenges decades of advice as it reveals fat has a PROTECTIVE effect”? That’s what happened on 30th August 2017. The headline came from the publication of something called the PURE study, which stands for the Prospective Urban Rural Epidemiology study. You can see the abstract (summary) of the publication here.

The PURE study

The PURE study is a large, epidemiological study of approximately 135,000 individuals aged 35–70 years in 18 countries with an average (median) follow-up of 7·4 years. The primary aim of the study was to assess the association of fats (total, saturated and unsaturated fats) and carbohydrate with total mortality and cardiovascular disease (CVD) events. The secondary aim was to examine associations between these nutrients and heart attacks, stroke, cardiovascular disease mortality and non-cardiovascular disease mortality.

The countries in the study covered five continents and extremes of affluence. Three high-income countries were included (Canada, Sweden, and United Arab Emirates), 11 middle-income countries (Argentina, Brazil, Chile, China, Colombia, Iran, Malaysia, occupied Palestinian territory, Poland, South Africa, and Turkey) and four low-income countries (Bangladesh, India, Pakistan, and Zimbabwe). The countries were also grouped by region: Africa (South Africa, Zimbabwe); China (on its own); Europe and North America (Canada, Poland, Sweden); Middle East (Iran, occupied Palestinian territory, Turkey, United Arab Emirates); south America (Argentina, Brazil, Chile, Colombia); south Asia (Bangladesh, India, Pakistan); and southeast Asia (Malaysia).

Table 1 followed the grouping by region and it presented the characteristics of each region (Africa, China, Europe & North America, Middle East, south America, south Asia and southeast Asia) for physical, health and lifestyle characteristics: age; gender; urban location; blood pressure; waist to hip ratio; smoking; education; physical activity; and history of diabetes. As the primary aim of the study was to review fats and carbohydrate and events, Table 1 reported the percentage of energy that came from fats (total and individual), carbohydrate and protein for each region. This alone was fascinating. China had the highest percentage intake of carbohydrate at 67%. Europe and North America, as a region, was lowest at 52%.

The paper reported in the Discussion section: “A high carbohydrate diet is usually accompanied by a low fat intake.” “Usually” is probably not quite strong enough. As protein tends to be fairly constant in any diet, the macronutrients that vary are fat and carbohydrate. One goes up, the other concomitantly goes down. Interestingly, Table 1 confirmed the very small variation in protein intake in all diets. Five of the seven regions, covering 75% of study participants, had protein intakes of between 15-17.5% of energy intake. Africa and south Asia had lower protein intake: 13.4% and 11.6% respectively.

Other interesting findings from Table 1 were: