Why the PURE study isn’t exactly pure science

And certainly not worthy of the headlines it’s getting

© Akakiy | Dreamstime Stock Photos & Stock Free Images

Here we go again: it seems that research that goes against the grain gets the most attention and make for the sexiest headlines. “Low fat diets could kill you, major study shows” is one that certainly catches your eye, wouldn’t you say? “Huge new study casts doubt on conventional wisdom about fat and carbs” states another accompanied by a photo of whole grain breads. Most of the other headlines were just as provocative while just a few did seem to provide a more balanced approach.

Wouldn’t it be great if the media would consult other experts in the field before publishing these kinds of messages but with time constraints and budget cuts, who can blame them for wanting to grab everyone’s attention?

But let’s set the record straight. Yes, low fat diets can kill you, especially when what’s being eaten is mainly unhealthy carbohydrate-rich options such as refined grains, not whole grains, fruits and vegetables and pulses like lentils and dried beans.

First, though, here are some of the study details.

The investigation, published in the journal Lancet, included more than 135,000 individuals from 18 low, middle and high-income countries and is known as the Prospective Urban-Rural Epidemiology (PURE). The countries included those from North America and Europe, South America, the Middle East, South Asia, China, South East Asia and Africa.

The study showed that high carbohydrate intake is linked to worse total mortality, while a high fat intake is associated with a lower risk of dying. So how do the scientists come up with such findings – I want to describe the findings with certain descriptives but I don’t like to use profanities in my posts.

The press release does provide clues. It states, “For this analysis, consumption of carbohydrate, total fat and types of fat were recorded using country-specific, validated food frequency questionnaires, and associations were assessed with CV disease and mortality.”

Notice the differences: the types of fat were indeed determined but they weren’t compared to the types of carbohydrates. That’s a pretty major comparison to leave out.

Hmmm – don’t the scientists know that you can’t compare eating white bread to having a carbohydrate-rich foods such as apples, brown rice and lentils? I would venture to say they do but they decided to conduct a study where they didn’t compare apples to apples.

Buried inside the many pages of the study, the authors state, “Moreover, in our study most participants from low-income and middle-income countries consumed a very high carbohydrate diet (at least 60% of energy), especially from refined sources (such as white rice and white bread), which have been shown to be associated with increased risk of total mortality and cardiovascular events.”

They also state “Moreover, North American and European populations consume a lower carbohydrate diet than populations elsewhere where most people consume very high carbohydrate diets mainly from refined sources.”


Poor people aren’t eating balanced diets with healthy carbs and fats along with protein. They’re eating mainly unhealthy carbs and as a result, their poverty is contributing to an earlier death.

But it’s important to note that the lower carbohydrate diet they refer to for North Americans and Europeans is NOT a low carb diet. Many North American and Europeans are not sitting down to a plate full of white rice with white bread on the side. But that’s not to say that there aren’t issues surrounding poverty and food insecurity in our populations because we certainly do have these problems here. We just don’t have the same numbers as are found in places like India and China, for examples – places that were included in this questionable research and compared to more affluent ones.

The paper also shows that monounsaturated fats, such as olive and canola oils were protective which is in keeping with other research. Also in keeping with other previously published large studies, replacing the carbs (remember those refined ones?) with polyunsaturated fat – think omega-3 in cold water fish and lots of nuts and seeds- resulted in an 11% lower risk of mortality.

So eating salmon and nuts such as walnuts and almonds instead of just white rice offers health benefits. Go figure!

Replacing the carbohydrate with saturated fatty acids – think butter and other animal fats – did not decrease the risk of dying.

The authors of the study state that we need to rethink the dietary fat recommendations. Where have these scientists been for the past few years? I’ve written about the findings of Harvard scientists with their large studies (of almost 130,000 subjects) numerous times over the past two years. It showed that people who replace saturated fat in their diets with refined carbohydrates do not lower their risk of heart disease. In addition, those who replace saturated fats with unsaturated fats or whole grains do indeed lower their heart disease risk.

There are many more issues about this study but I’ve already wasted enough of both your and my time.

I guess all I can say about the health implications of research such as the PURE study is that it’s linked to high blood pressure – those health experts who read this kind of nonsense and have to refute it. Even maddening doesn’t quite describe it as the criticisms of the research won’t get any attention compared to the nonsense.

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Categories: Nutrition News, Rosie's Rants

Author:Rosie Schwartz

Rosie Schwartz is a Toronto-based consulting dietitian and writer.

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5 Comments on “Why the PURE study isn’t exactly pure science”

  1. August 31, 2017 at 8:15 am #

    Thanks for this Rosie! As always, I appreciate your insight and helping us understand what’s really behind the headlines.

  2. August 31, 2017 at 2:40 pm #

    My pleasure, Getty! Thanks for the feedback. I wish we didn’t have to clarify such ridiculous research!

  3. Christine
    August 31, 2017 at 4:44 pm #

    Good work Rosie! My husband will be disappointed as he was so happy to tell me how my avoiding fats while opting for healthier choices will not keep me at a lower risk…. He thought the article we saw in paper mean green light for his bacon, etc…

    • September 3, 2017 at 1:46 pm #

      Glad to be of assistance, Christine! Ha! In any case, a lot of people were confused by all the reports. James Hamblin wrote a great overview of these kinds of studies in the Atlantic. It would be good to give it to your husband! http://theatln.tc/2wvCsuk

      • Christine Veziina
        September 4, 2017 at 6:15 pm #

        Will certainly pass it on to him!

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