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Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...

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September 04, 2017

Dear Mark: The PURE Study

By Mark Sisson
22 Comments

magnifying glass on black texture background.For today’s edition of Dear Mark, I’m addressing just one question. It’s not even a question, really. It’s a study. In the comments to a post from last week, Pedro dropped a line about some very cool research.

Hello Mark. No miss: http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(17)32252-3/abstract

No way would I miss that one, Pedro. Thanks for the note.

This wasn’t quite a question, but it gives good fodder for me to riff on a few things.

First, as I have said for a decade “The less glucose you burn in a lifetime, the healthier you’ll be and the longer you’ll live.” A new study—the PURE study—seems to hint at that. They looked at the dietary intakes of over 135,000 individuals from 18 countries with an average followup of about 7.5 years. They saw what people said they ate then watched what happened to them.

Turns out that people who ate the most carbs had the highest risk of dying.

People who ate more saturated fat than is recommended (under 10% of energy) had longer lives.

People who ate more protein (even animal) also lived longer.

People who ate fruits, vegetables, and legumes lived longer, too, but the benefits plateaued at around 3-4 servings a day after adjusting for variables like education, income, smoking, and exercise.

This is a great study. It appeals to us. It hits pretty much every point we’ve been saying for years.

However…

We have to exercise the same restraint and skepticism with this study that we show when observational studies claim the opposite: that meat is deadly and saturated fat will destroy us all. Many of the same issues apply here.

For example, the unreliability of food frequency questionnaires (FFQs). That’s where you have to fill out a form describing what you ate and how often over the last 12 months. Here’s a sample FFQ (PDF), to get an idea of what they expect people to remember. They aren’t very reliable. People lie. People forget. People tell you what they think you want to hear, downplaying the unhealthy stuff and overstating the healthy stuff. While this last factor is less relevant in studies where the “unhealthy stuff” turns out to be good for us, it’s still a mark against.

Another is the simple fact that it’s an observational study that cannot prove cause and effect.

Of course, some of the study’s critics make mistakes. Katz had one of the most dishonest takes on a major aspect of PURE. The real kicker was his description of non-cardiovascular mortality:

An alleged “surprise” in the PURE data is that higher intake of saturated fat was associated with lower mortality overall. Here, too, however, higher saturated fat intake- which occurred together with higher protein intake- was associated with much reduced risk of non-cardiovascular death. So, does eating more saturated fat protect you from dying when run over by an ox- or does being in a place with access to more saturated fat (i.e., animal food) in the diet mean you eat the ox before he can run you over? And, that, if ever he does run into you- there’s a hospital somewhere reachable?

He plays similar games with other associations between dietary intakes and “non-cardiovascular death.” Katz knows “non-cardiovascular death” doesn’t just mean accidental or violent deaths. It means deaths from diabetes, cancer, and everything else including, yes, accidents and violence. Which do you think causes more “non-cardiovascular” deaths—goring by ox or untreated diabetes? Trampled by yak or colon cancer? Crushed by wildebeest stampede or lung cancer?

But Katz doesn’t mention those other, more common non-cardiovascular deaths. Most people reading his article won’t consider them. It’s not a lie, not technically, but it’s close. He misleads via omission.

That said, he proposes an interesting explanation:

Animal protein and saturated fat consumption were markers of affluence and access to health care. People who ate more of both were healthier because they were wealthier, had access to other healthy (expensive) foods, and could go to the doctor, not because of some intrinsic quality of the nutrients themselves. Those who ate less were poorer, sicker, and more reliant on processed, refined foods.

That could be part of it. I wouldn’t be surprised. The 18 countries were all over the map and included high income (Canada, Sweden, UAE), middle income (South Africa, Turkey, China, Argentina, Poland, Colombia, Iran, Malaysia, Chile, Brazil), and low income (India, Bangladesh, Zimbabwe, Pakistan, Palestinian Territories) nations. The food and health situations vary wildly across those countries.

Yet for the PURE study, researchers corrected for those socioeconomic variables. They corrected for household income and wealth, for economic status of the country of residence. They corrected for just about everything you can imagine, and the results persisted.

One of the biggest criticisms I lob against the typical observation study “proving” the danger of saturated fat/animal protein/egg yolks is the healthy user bias. Animal foods have the reputation as being terrible for your health. “Everyone knows” whole grains are healthier than steak and eggs. Thus, the people who eat more saturated fat/animal protein/egg yolks are also more likely to be sedentary, to smoke, to drink too much, to avoid vegetables, and to do all sorts of other unhealthy things.

The most impressive part of the PURE study is that the benefits of saturated fat/animal protein/fewer carbs survived the healthy user effect. Despite “everyone knowing” that they’re deadly, those who ate more of them still lived longer. That’s powerful.

But don’t get cocky, kid. There’s a lot we don’t know. We can’t hang our hats on the newest, biggest, bestest, bias-confirmingest observational study, just as we can’t hang our heads in despair at the latest observational study to attack our biases.

Go with results. Go with what works for you. Go with what feels right and helps you perform at your best.

What else is there?

Thanks for reading, everyone. Take care. I’d love to hear your take on the study.

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22 Comments on "Dear Mark: The PURE Study"

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Shary
Shary
20 days 4 hours ago

“People lie. People forget. People tell you what they think you want to hear…”

Exactly. This is why all questionnaire type studies are suspect and often further skewed in order to achieve a specific result. I’ve never understood why people are willing to put so much faith in them. Mark’s advice of “Go with what works for you” is the only thing that makes any sense. Stick with what your body tells you and ignore the studies.

Joanna
Joanna
20 days 4 hours ago

Thank you, thank you for mentioning that it’s still an observational study based on self reports! I have been seeing great enthusiasm for this study all over the web from people who would JUMP all over the “association is not causality” argument if it went the other way. So I appreciate your consistent standards!

jackisback
jackisback
19 days 2 hours ago

This is exactly what I was going to say, but clearly I am not the only one who has an issue with accepting observational studies, so long as they confirm your point of view. Just because we are right, doesn’t mean we can be hypocritical. I’m glad Mark recognized this too.

Margaret
Margaret
20 days 3 hours ago

Sorry, Mark, but a couple of editing quibbles:

“highest risk of death” — we alll have the same risk of death, no? Did you mean early mortality?

Also, you introduce this Katz person, last name only, without saying who he is or why his opinion would be of importance.

JJill
20 days 1 minute ago

Risk of death during the study. Remember there is a finite period to the study.

Margaret
Margaret
19 days 21 hours ago

Got it, thanks. I should read more slowly.

Erin KC
Erin KC
19 days 22 hours ago

David L. Katz, Yale. He’s a snarky piece of work, that one. Google “pure study Katz” to find his rebuttal of the Lancet papers.

Margaret
Margaret
19 days 21 hours ago

Thanks. I read a couple of his writings, and admit I didn’t find him any snarkier than Mark is at times.

tribal
tribal
19 days 13 hours ago

Snarky: “snide and sharply critical” – I have not found Mark to be to this definition.

Jeff
20 days 3 hours ago

Observational studies need to be followed up by RCT’s to be verified, but RCT’s that involve shortened lifespan are unethical and hence will never happen. So we are unlikely to ever do much better than studies like PURE.

Ryan Smith
20 days 2 hours ago

Thanks for the work!

Elizabeth Resnick
20 days 2 hours ago
Great post. I pulled up the study last night after seeing it mentioned in Weekend Link Love. Totally agree that asking people to recall what they ate can’t be that accurate. And bottom line, as Mark says at the end “Go with results. Go with what works for you. Go with what feels right and helps you perform at your best.” That’s why I eat and live the way I do,and am constantly fine tuning and trying new things Science is great but it all comes down to how you feel. I’m more and more keto all the time and… Read more »
JJill
20 days 10 minutes ago

So can we replace the “seven countries study” with this 18 countries study for good? Grandma and Grandpa were right. Bacon and eggs every day of their life, Beef for dinner and supper with home grown green beans, cucumbers and tomatoes.

HealthyHombre
HealthyHombre
19 days 23 hours ago

Longevity and quality of life is a complex topic and optimizing it has many variables even more important than diet and exercise I’m finally understanding (which are key factors, don’t get me wrong) like sleep quality, stress reduction, avoiding toxins, a sense of purpose and community, and spending as much time in nature as possible. Just study the lifestyle / diet etc. of folks in the Blue Zones to get the real answers IMHO.

Lauren Romeo, MD
Lauren Romeo, MD
19 days 23 hours ago

Thanks for the review. I tend to send folks over to your site and recommend your book to start their journey towards better health. As an aside I have been gluten free 37 years due to Celiac Disease, I also, went sugar free ten years ago. Now a lot of people ask me how and why I recommend this same way of living for everyone. My answer is better health, more vitality, more or less wrinkle free skin, less indigestion and more creativity in my life! Keep up the good work!

David
David
19 days 17 hours ago
“The most impressive part of the PURE study is that the benefits of saturated fat/animal protein/fewer carbs survived the healthy user effect. Despite “everyone knowing” that they’re deadly, those who ate more of them still lived longer. That’s powerful.” I understand the healthy user effect for people living in westernized countries but I wonder how much brainwashing of the message “saturated fat and red meat = bad; fruits and veggies = good” there exists in many of the 18 countries in the study? Did Ancel Keys 7 countries study really effect the diets of people living in Turkey, Poland, Bangladesh,… Read more »
tribal
tribal
19 days 13 hours ago

so in terms of cross fit – previous articles here have recommended that its not possible to maintain an intense cross fit schedule without eating more carbs. But more carbs = more sugar = less life according to this study.

Maybe it comes back to the old adage: “The candle that burns twice as bright burns for half as long” – so achieving extreme cross fit objectives may literally demand payment in years of life.

Mathieu
Mathieu
19 days 12 hours ago

“But more carbs = more sugar = less life according to this study.”

Read again…

Stefan M
Stefan M
19 days 9 hours ago
I don’t think carbohydrates are a problem for those that store or burn it immediately — they’re only oxidizing in our blood environment, right? Those that are carb-deplete after a tough workout NEED their carbs, and while there’s something to be said for longevity gene expression when you reduce carbs AND calories, I don’t think carb-loading by necessity after anaerobic exercise has any DETRIMENTAL expression by itself. See Okinawans, who have a diet of 70-80% carbohydrates consisting of ~1800 calories. I think there’s something to be said about mTOR activation on a high-carb, high-calorie training diet… But I think fasting,… Read more »
Mary
Mary
18 days 18 hours ago

“Turns out that people who ate the most carbs had the highest risk of dying.” I like your analysis, Mark, but hate to be the bearer of bad news – no matter how many carbs we eat, we all have the exact same risk of dying: 100%. I’m sure you mean they had a higher risk of dying earlier than expected.

Caitlin Lee
Caitlin Lee
17 days 3 hours ago

JJill2 days 19 hours ago
“Risk of death during the study. Remember there is a finite period to the study.”

Kent
Kent
18 days 4 hours ago

This is great. I had heard of Dr. Katz before but had not read much of his work. I read his response to the PURE studies mentioned here which led me to a few of his other articles. It was pretty apparent right away that he leans towards sat-fat-phobic. In fact, one article he wrote was based on a study by the American Heart Association in which they recommended replacing saturated fat with vegetable oil, thus reducing CHD by 30%. Yes, the same American Heart Association which puts its label on the outside of a cereal box.

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