Social media has been abuzz the last few weeks about the 5 Continent PURE Study. The findings of the study, which analyzed nutrition intake data from over 135,000 people in 18 countries, have seemingly contradicted long held beliefs about the risk associated with carbohydrates and fat. Key word “seemingly.”
What is the “PURE Study?”
The pure study ran for 10 years, from 2003 to 2013, and followed over 135,000 people in 18 countries. Those countries – spanning a wide range of income levels – include Canada, Sweden, UAE, Argentina, Brazil, Chile, China, Colombia, Iran, Malaysia, Palestine, Poland, South Africa, Turkey, Bangladesh, India, Pakistan, and Zimbabwe.
The average person was followed for about 7 years, but the study is still ongoing so more data should be available in the future.
What did the PURE study find?
In a nutshell, the basic findings were that:
- Total carbohydrate intake was linked to higher risk of total mortality (or, dying of anything from a heart attack to a car accident). There was no link between carb intake and CVD or death from CVD.
- Intake of both total and each individual type of fat was linked to lower risk of total mortality (again, death from any cause).
- Saturated fat was linked to lower risk of stroke.
Revolutionary, right? Not so fast my friend.
Let’s start with how comparisons were made. The data from participants was split into quintiles, and the risk was assessed comparing the highest and lowest quintile. So for carbohydrates, the highest fifth ate about 74-80% of daily calories from carbohydrates, while the lowest was around 42-49%. Between those two groups, there was a 1.28 hazard ratio (a hazard ratio of 1 would mean the risk was the same). It’s also worth remembering that there was no link between carbohydrate intake and heart disease or death from heart disease, just total death from all causes.
When it came to fat, the highest quintile was eating about 13% of calories from saturated fat, which is only a little over the recommended 10%, and those between 9 and 10% had similar risk to their peers at 13%.
So basically, this study tells us what we already know: very high carbohydrate intake above the upper limits of generally accepted dietary guidelines incur risk. Remember that the United States Dietary Guidelines recommend 45-65% of intake from carbohydrates. I don’t have access to the full text, but I’d be curios to see the comparisons between the 2nd and 3rd quintiles and the first. Is there still a statistically significant association when carb intake reaches recommended levels?
For a few other great points about the study results, read an assessment from fellow dietitian Nutrition Wonk over at her page.