mprevost
Level 7 Valued Member
My take on the PURE study that is creating so much media buzz lately......... You may have seen the headlines...New study finds high fat beneficial..low saturated fat intake deadly....
PURE study is the Prospective Urban Rural Epidemiology study. The study, published in the prestigious journal Lancet here generated a huge amount of press due to the findings on carbohydrate and saturated fat consumption. One of the defining characteristics of the study was the large size, 135,000 subjects!
What were the interesting findings? Probably the most significant and interesting findings were those concerning carbohydrate and saturated fat as they related to mortality (death).
Saturated Fat and Risk
Take a look at the image above. This is the saturated fat data. The vertical axis is relative risk. Everything above the black dotted line equals increasing risk and below the black dotted line equals increasing risk reduction (and protection). What you should see is that at very low intakes of saturated fat, risk of cardiovascular disease is higher (but just slightly), and adding saturated fat reduces risk of mortality, but the benefit plateaus by about 7% of calories from saturated fat. You can see that once you reduce saturated fat intake below 6% of calories, you start to lose benefit and at the lowest intake level, you are at greater risk.
Carbohydrates and Risk
Above is the carbohydrate date. It is a bit more striking, because the effect is a bit bigger. There is not much action until you get to about 70% of calories from carbohydrates, then risk increases sharply with increased intake.
Taken together what these data conclude is that the highest consumption tertile group (highest 20%) for carbohydrates was associated with increased risk of cardiovascular disease and death and that the lowest tertile consumption of saturated fat was associated with increased risk. So, more carbs = more risk, less saturated fat = more risk?
Well, not exactly. If you look closely at the saturated fat graph again, you’ll see that there really wasn’t much impact from different saturated fat intakes until the intake got really small. So we might conclude that saturated fat intake does not have a significant impact on major cardiovascular disease and death (but with a small trend towards protection) unless saturated fat intake is very low (approx. less than 3% of your caloric intake) and in that case you might be a slightly greater risk. In the carbohydrate data, the increased risk occurred at intakes above 70% of calories. Below that value there was no significant impact.
In my opinion, the biggest story in the saturated fat data is not the increased risk at low intakes, but the failure to show greater risk with higher intakes. This runs contrary to the message we have received from most health organizations for the last 30 years! The carb data is less exciting than it appears. The increased risk begins at about 70% of calories from carbohydrates. The average American is closer to 50%, so according to this data, the average American’s carbohydrate intake is in the neutral risk zone.
So what is the take away? Ignore the media hype about how this study shows that increased carb intake leads to increased mortality. The level of carb intake that increased risk in this study is too high to apply to most of the population, so that finding is not relevant to most. Also, ignore the hype about low saturated fat intake increasing mortality. The impact was very small and only for very, very low saturated fat intake (less than 3% of calories) so this likely does not apply to most Americans either.
The real story here, and it is a big one, is that increased saturated fat intake was not associated with increased risk of cardiovascular disease and death. That is big news and worth talking about.
Finally, I should mention that the criticisms of the study are starting to accumulate but all studies of this type are subject to these types of limitations.
Dehghan M, Mente A, Zhang X, et al, on behalf of the Prospective Urban Rural Epidemiology (PURE) study investigators. Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study. Lancet 2017; published online Aug 29.
From my site (New Study on Saturated Fat Getting Lots of Media Buzz – Mike Prevost, PhD)
PURE study is the Prospective Urban Rural Epidemiology study. The study, published in the prestigious journal Lancet here generated a huge amount of press due to the findings on carbohydrate and saturated fat consumption. One of the defining characteristics of the study was the large size, 135,000 subjects!
What were the interesting findings? Probably the most significant and interesting findings were those concerning carbohydrate and saturated fat as they related to mortality (death).
Saturated Fat and Risk
Take a look at the image above. This is the saturated fat data. The vertical axis is relative risk. Everything above the black dotted line equals increasing risk and below the black dotted line equals increasing risk reduction (and protection). What you should see is that at very low intakes of saturated fat, risk of cardiovascular disease is higher (but just slightly), and adding saturated fat reduces risk of mortality, but the benefit plateaus by about 7% of calories from saturated fat. You can see that once you reduce saturated fat intake below 6% of calories, you start to lose benefit and at the lowest intake level, you are at greater risk.
Carbohydrates and Risk
Above is the carbohydrate date. It is a bit more striking, because the effect is a bit bigger. There is not much action until you get to about 70% of calories from carbohydrates, then risk increases sharply with increased intake.
Taken together what these data conclude is that the highest consumption tertile group (highest 20%) for carbohydrates was associated with increased risk of cardiovascular disease and death and that the lowest tertile consumption of saturated fat was associated with increased risk. So, more carbs = more risk, less saturated fat = more risk?
Well, not exactly. If you look closely at the saturated fat graph again, you’ll see that there really wasn’t much impact from different saturated fat intakes until the intake got really small. So we might conclude that saturated fat intake does not have a significant impact on major cardiovascular disease and death (but with a small trend towards protection) unless saturated fat intake is very low (approx. less than 3% of your caloric intake) and in that case you might be a slightly greater risk. In the carbohydrate data, the increased risk occurred at intakes above 70% of calories. Below that value there was no significant impact.
In my opinion, the biggest story in the saturated fat data is not the increased risk at low intakes, but the failure to show greater risk with higher intakes. This runs contrary to the message we have received from most health organizations for the last 30 years! The carb data is less exciting than it appears. The increased risk begins at about 70% of calories from carbohydrates. The average American is closer to 50%, so according to this data, the average American’s carbohydrate intake is in the neutral risk zone.
So what is the take away? Ignore the media hype about how this study shows that increased carb intake leads to increased mortality. The level of carb intake that increased risk in this study is too high to apply to most of the population, so that finding is not relevant to most. Also, ignore the hype about low saturated fat intake increasing mortality. The impact was very small and only for very, very low saturated fat intake (less than 3% of calories) so this likely does not apply to most Americans either.
The real story here, and it is a big one, is that increased saturated fat intake was not associated with increased risk of cardiovascular disease and death. That is big news and worth talking about.
Finally, I should mention that the criticisms of the study are starting to accumulate but all studies of this type are subject to these types of limitations.
Dehghan M, Mente A, Zhang X, et al, on behalf of the Prospective Urban Rural Epidemiology (PURE) study investigators. Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study. Lancet 2017; published online Aug 29.
From my site (New Study on Saturated Fat Getting Lots of Media Buzz – Mike Prevost, PhD)
