Do high saturated fat diets lead to heart disease? | Peter Attia and Don Layman

Summary

The transcript covers a discussion between two individuals reflecting on the research legacy of Ancel Keys at the University of Minnesota. They review Keys' famous seven countries study linking dietary saturated fat to heart disease, as well as his human starvation experiments. The discussion centers around analyzing and interpreting Keys' 1970s Minnesota Coronary Experiment which compared a high saturated fat diet to a high polyunsaturated fat diet in institutionalized patients. Though the polyunsaturated fat group had lower cholesterol, there was no difference in cardiac events after 5 years. They debate the meaning of these results in light of subsequent research questioning saturated fat's link to heart disease.

Takeaways

• 😊 Don wasn't an expert on lipids but remembered the Minnesota Coronary Experiment study
• 🧐 The evidence on saturated fat and heart disease has been mixed overall
• 🤔 The cholesterol and saturated fat hypotheses have weakened over time
• 😮 A seminar speaker warned about trans fat dangers years before policies changed
• 🤨 The Minnesota study found no difference in events despite cholesterol changes
• 😕 Ansel Keys had major influence on diet-heart disease ideas at Minnesota then
• �ToString The Minnesota study may have been too short to show diet effects
• 🤔 Don believes calories matter most for obesity, macros for lean healthy people
• 😒 Selective publishing and excuses maintained diet-heart hypotheses over time
• 🤷‍♂️ Saturated fats don't seem problematic for weight-stable people

Q & A

What were the two things Ancel Keys was famous for when the narrator was at the University of Minnesota?

Keys was famous for the seven country study, which promoted the idea that saturated fat in the diet causes heart disease, and for starvation experiments done in the 1940s or 1950s to study the effects of starvation on the human body.

What did the narrator start to realize about the diet-heart hypothesis as he conducted research early in his career?

The narrator started to realize he didn't really believe the hypothesis that saturated fat and cholesterol cause heart disease, based on experiments he did involving fasting and malnutrition.

What happened after Fred Kummerow suggested at a Minnesota seminar that cooking oils and trans fats were dangerous?

Kummerow was ridiculed at the seminar, but 20 years later trans fats were banned from foods as the most dangerous type of fat.

What were the two diets compared in the Minnesota Coronary Experiment conducted by Ancel Keys?

One diet was high in saturated fat and one was high in polyunsaturated fat. The goal was to see if the diet lower in saturated fat would reduce risk of heart attacks and strokes.

What were the main results of the Minnesota Coronary Experiment?

After 5 years there was no difference in cardiovascular events between the high saturated fat and high polyunsaturated fat groups, even though cholesterol levels were lower in the polyunsaturated group.

Why does the narrator think the Minnesota Coronary Experiment may have been underpowered?

The narrator initially thought 5 years may not have been long enough to appreciate a difference in events between the diet groups if one existed.

What did further analysis of the Minnesota Coronary Experiment data show?

Further analysis showed some subgroups actually had more coronary events on the high polyunsaturated fat diet.

What is Dr. Layman's view on the diet-heart hypothesis related to saturated fat?

Dr. Layman believes the evidence on saturated fat and heart disease is mixed and the hypothesis has weakened over time as better studies are done.

What does Dr. Layman believe is most important if your goal is to be lean and healthy?

If the goal is to be lean and healthy, Dr. Layman believes total calories are what matters most, not the breakdown of macros.

When might saturated fat quality start to matter more according to Dr. Layman?

If someone is committed to being obese, Dr. Layman says saturated fat quality would become more important to consider.

Outlines

00:00

😃 Keys' Work and Influence at University of Minnesota

Paragraph 1 discusses Ancel Keys' reputation and influence at the University of Minnesota when the author was there. Keys was known for his seven countries study linking dietary fat to heart disease, and his starvation experiments. The author initially bought into Keys' hypotheses but over time through his own research realized he did not actually believe them. A seminar is recalled where Keys' colleague ridiculed a speaker warning about trans fats, which were later banned.

05:02

😕 Interpreting the Minnesota Coronary Experiment

Paragraph 2 examines the Minnesota Coronary Experiment study by Keys which compared high saturated fat to high polyunsaturated fat diets. Though the polyunsaturated group had much lower cholesterol, there was no difference in cardiac events. Keys did not publish the full data which was later released, showing higher events in some polyunsaturated fat subgroups. The author discusses potential reasons for the perplexing results and gets input from the guest who also cannot definitively interpret the data.

Keywords

💡Dietary Fat

Dietary fat refers to fats and oils consumed in the diet. The video discusses beliefs in the 1970s that saturated fat caused heart disease. Keys had published studies linking saturated fat to cardiovascular disease. The Minnesota Coronary Experiment compared diets high in saturated fat versus polyunsaturated fat to test this hypothesis.

💡Cholesterol Theory

The cholesterol theory hypothesizes that consuming saturated fat raises blood cholesterol, particularly LDL cholesterol, which causes atherosclerosis and heart disease. The video explains how evidence for the cholesterol theory has weakened over time as clinical trials have failed to show benefit from reducing saturated fat.

💡Minnesota Coronary Experiment

A landmark study in the 1970s conducted by Ancel Keys testing whether replacing saturated fat with polyunsaturated fat reduced cardiovascular events. Despite lowering cholesterol, the diet higher in polyunsaturated fat did not reduce cardiovascular events, contrary to the cholesterol theory.

💡Cardiovascular Disease

Encompasses heart disease and stroke. The research discussed focuses on coronary heart disease related to atherosclerosis. The studies aim to understand how diet impacts risk of cardiovascular disease.

💡Total Cholesterol

A measurement of the amount of cholesterol circulating in the blood. In the 1970s, total blood cholesterol was used as a risk factor for heart disease. The Minnesota Coronary Experiment found that lowering total cholesterol via diet did not reduce cardiovascular events.

💡Calories

A measurement of the energy content in foods. The video explains that if calories are controlled, the evidence does not support a harmful effect of saturated fat for health.

💡Obesity

Accumulation of excessive body fat. The video suggests that for those struggling with obesity, fat quality may be more important while for lean individuals, total calories are more important.

💡Polyunsaturated Fat

A form of dietary fat found in foods like vegetable oils and fish. The Minnesota Coronary Experiment used a diet high in polyunsaturated fat from safflower oil to try to improve heart health compared to saturated fat.

💡Saturated Fat

A form of dietary fat found mainly in animal foods like meat and dairy. Believed in the 1970s to raise cholesterol and lead to heart disease. Key focus of the Minnesota Coronary Experiment.

💡Trans Fats

Artificial form of fat produced by hydrogenation of vegetable oils. The video describes trans fats as very harmful, exemplifying how the lipid hypotheses have evolved over time.

Highlights

Keys was famous for his seven country study and saturated fat-CVD hypothesis, as well as the starvation experiments in the 1940s/50s.

Learned that questioning established dogma is important - people bought into saturated fat and cholesterol theory aren't necessarily right.

In 1973, Ivan Frantz published the Minnesota Coronary Experiment comparing high saturated fat to high PUFA diets in institutionalized patients.

The diets differed only in fat type, not total calories or macros - but the PUFA group had 30mg/dL lower total cholesterol.

After 5 years there was no difference in cardiac events, despite lower cholesterol in PUFA group.

Frantz didn't publish the null results as they didn't match his hypothesis that lower saturated fat would reduce events.

Ramsden re-analyzed the data years later, showing no benefit of PUFA and potential harm in some subgroups.

The total cholesterol and saturated fat hypotheses have gotten weaker over time.

If calories are controlled, there's little evidence saturated fats are problematic.

For weight loss, calories are key - macro distribution is personal preference.

The Women's Health Initiative showed mixed results regarding saturated fats.

Those invested in the hypothesis try to explain away null findings rather than questioning it.

A correct scientific theory gets stronger over time, an incorrect one gets weaker.

Excess calories alongside excess saturated fat is likely problematic.

For leanness and health, calories are the priority.

Transcripts

let's go pick it up back in University

of Minnesota you've got the Legacy and

I'm guessing at the time you know Keys

is really famous for two things in the

mid-70s right I think by that point he's

probably already published his seven

country study and the the hypothesis now

is a very fat Centric view of you know

the the negative consequences of dietary

fat specifically dietary saturated fat

in the American diet especially as it

pertains to

ascvd and then I suspect the second

thing that he's probably still famous

for is the starvation experiments um

that were I'm guessing done in the 1950s

I mean these were done on conscientious

obur so they're probably in the 40s or

50s

right yeah I I can't exactly date that

but you're exactly right so those were I

mean we learned a lot

about starvation at that point for

obvious reasons we can't Dukes

experiments like that before but we

learned a lot about body composition and

how the body starve so were good but

certainly the Legacy was there and when

I got to Minnesota you know I sort of

bought into the cholesterol and the

saturated fat and total fat and you know

I I sort of okay this is what

everybody's teaching and you know that's

what I was forced to learn that's what

they were teaching uh and so I bought

into it but you know as I slowly started

doing experiments and early in my career

we did a lot of fasting type of

experiments with animals to look at

composition change and I did

malnutrition work in in Northern Africa

and I sort of got into all of that and I

I I started realizing you know I don't

really believe that and one seminar I

will always remember at Minnesota was

individual by their name of Fred Kumo

came to Minnesota and gave a seminar

about the dangers of cooking oils and

specifically trans fats and Blackburn in

France just ridiculed him B basically

said this is the craziest thing we've

ever heard all these plant oils are

great uh and basically you know 20 years

later we ban trans fats from Foods

literally as the most dangerous fat that

you can encounter so I I always remember

that just sort of thinking well you know

people who have bought into this Dogma

aren't necessarily right and we need to

keep questioning it speaking of FRS um

obviously in

1973 he completes a study the Min

Minnesota coronary

experiment um I I actually find this to

be one of the most difficult studies to

interpret not so much the one that he

published 16 years later by the way in

1989 but the one that Chris Ramden

republished just a couple of years ago

based on all of the data from France's

study Plus data he never

published this to me is one of the most

complicated stories and I I will tell

you I have posed this question to every

friend of mine who is more steeped in

nutrition than I am and um I still don't

have a great sense of how to explain

these results so I'll explain it for the

for the listener and the viewer and I'm

curious to your thoughts so the

experiment was done um in basically

institutionalized patients so again

maybe not a study that could be done

easily again today for ethical reasons

but had the advantage of being so well

controlled you you basically had

patients that were randomized into two

groups their total energy was identical

their total split of macronutrients was

identical the only thing that differed

was that in one group it was high

saturated fat and in the other group it

was high polyunsaturated fat the

hypothesis being tested was is saturated

fat intake leading to increased major

adverse cardiac events heart attacks and

strokes the experiment that completed in

I think it ran I I can't remember

exactly I think it ran about five years

in 1973 showed no difference there was

no difference in cardiac events despite

the fact that the group that was on the

higher polyunsaturated fat group did

indeed have much lower cholesterol

levels now this was this predated the

subf fractionation so they weren't

measuring LDL and HDL they were just

measuring total cholesterol and at the

time there was some correlation between

cardiovascular disease and total

cholesterol levels at the extremes that

was certainly

true again because I didn't think we'd

be talking about this I don't have the

numbers all in my mind but we'll link to

it all but directionally I believe that

the higher Pua group relative to the

saturated fat group was about 30

milligrams per deiler lower in total

cholesterol and based on everything we

know today we would assume that much of

that was in LDL cholesterol indeed being

lower and non-hdl cholesterol and yet

there was no difference in events and of

course it's become a very famous and

unfortunate story in nutrition research

and that France chose not to publish it

because he didn't like the results it

didn't match his hypothesis which was

that the group on Lower saturated fat

would have fewer events Ramden went and

published all of these data plus a whole

bunch of subdata as I said just a few

years ago I believe in the British

medical journal and I actually found

something that

was that threw a wrench in my initial

hypothesis my initial view of the

Minnesota Corner experiment was it

probably wasn't a long enough

intervention it might be that 5 years

was not long enough to appreciate a

difference and so it was underpowered or

Too Short in a duration to see a benefit

if there was a

benefit but in Ramon's analysis you

actually saw the opposite because he now

looked at some subgroups and you

actually saw a higher incidents of

coronary events in some of the people

that were consuming the high

polyunsaturated fat diet and I can't

remember what the dominant oil was I'm

blanking on it I don't remember if it

was canola or safflower I think it was

safflower so how much of that do you

remember Don from your time there and

can you can you shed any light on this

or do you have any thoughts on you know

how to interpret that experiment well

first of all I am definitely not a lipid

expert so

um I you know I sort of remember the

study but I can't put any more numbers

to it than you did I actually did some

research with Ivan France and Penny

Chris Etherton when I was at Minnesota

so I you know I sort of was in the loop

at the time but that's been a couple of

years ago um yeah I think if one really

looks at the literature on saturated fat

and is fair about all of those studies

you find a very mixed bag the women's

health initiative and all of those kinds

of things uh and unfortunately the

people who believe the hypothesis have

either delayed publishing it or said

well it couldn't have been wrong and

tried to you know it could have been

wrong and they tried to find all kinds

of excuses as opposed to just believing

it U you know there's an old theory in

science that you know if the theory is

correct it'll get stronger over time and

if it's not it gets weaker and I think

one would have to

realize that a the cholesterol Theory

the total cholesterol theory has

definitely gotten weaker and the

saturated fat hasn't held up very well

um you know we still believe it but your

comment a little bit ago it's first and

foremost calories if you put excess

saturated fat on top of too many

calories that's probably a problem but

if you're at or below your calorie needs

I don't see any data that suggests it is

so you know my sort of joke or comment

all the time is that if you're committed

to being obese you probably ought to pay

attention to the quality of your fats

but if your goal if your goal is to be

lean and healthy calories is what you're

paying attention to and the macro

distribution is sort of your personal

[Music]

preference