Don't let the headlines fool you: The PURE study
Updated: Nov 24, 2019
This week's controversy is the data from the 'PURE' study. This cohort study covered individuals aged from 35-70 years old from 18 different countries, a total of 135,335 people. They concluded that with the highest intake of carbohydrates (77% of daily calories), they were likely to see increased mortality. On the other hand, with the highest intake of fat (35% of daily calories), they were less likely to an association with increased mortality. The size of the study makes the conclusion convincing but some of the findings are contradicting other large studies such as the China study (if you aren't aware of it then check it out!). On reviewing the study, there are four key areas that should be highlighted:
1. Carbohydrates. In PURE's study, the participants consuming the high carbohydrate intake were mostly from low and middle income countries. They tended to consume a high carbohydrate diet based on refined carbs, such as white rice and white bread. It is very important to address the quality of the carbohydrates e,g from whole plant foods, rather than the quantity.
2. Fats. This study does categorise fats into saturated, monounsaturated and polyunsaturated fats. However they did admit that trans fat intake was not monitored and it might affect their results base. As we know trans fats increases the risk of heart attacks. stroke and type 2 diabetes. Trans fats also have a negative effect on LDL and HDL cholesterol.
3. FFQ. In this study, they used FFQ to estimate participants dietary intake. Simple dietary questionnaires were used as a baseline, this did not take into account that people's life and dietary habits may have changed throughout the 7 years, as such the accuracy of the results could be questioned.
4. Poverty. Most participants from the low income countries were on the high carbohydrate diet, especially from refined sources. Poverty and the impact of poverty was not considered in this study. The living conditions, quality of food and water sources and general lifestyle factors were not discussed. The study showed us that in Bangladesh, white rice was not only the top food source for carbohydrates but also protein and fat. It is crucial to include the effect of poverty and food availability.
My conclusion is that even though this study is large, I don't think the data is controlled enough to take a conclusion from it. It did not take into account the quality of the diet and from where the participants were getting their carbohydrates or fats. We also don't know what impact diet is having versus healthcare and/or lifestyle or other. You could potentially conclude that diets high on refined carbohydrates are linked to increased mortality rates but a more controlled study would be needed.
So my point is if you see a article, also check the sources. The media are very good at creating headlines, they are in the business of having people read/watch their content.
When you see a research paper, read it, understand it. don't just read the headlines and the abstract.
Don't let the headlines fool you!