The Diet-Heart Hypothesis – Hormonal Obesity XXXV

With the publication of Dr. Key’s Seven Country Study, the origins of the Diet-Heart Hypothesis were laid down.  The major problem was that this was all observational data, and as such, was subject to severe interpretation.  There is nothing more dangerous in medicine than the correlation study.  It cannot be used to prove a hypothesis, only to disprove one.

For example, looking at the same data as Dr. Keys, others came to completely different conclusions.  While saturated fat was correlated to heart disease, most of it was the influence of animal fats.  Vegetable fats were not correlated at all.  But it wasn’t merely animal fats, but also animal protein that had correlation to heart disease.  So maybe it was animal products – ie. red meat dilemma.  Keep in mind that this does not exonerate vegetable fats.  Most people were eating nut oils and olive oil, not the highly processed corn oil, canola and vegetable oils that would come to dominate the American supermarket shelves.

However, it is also possible that animal consumption was merely a marker for industrialization.  Counties with higher levels of industrialization tended to eat more animal products – meat and dairy.  So, are you saying that the more Westernized countries had more Western diseases?  Hmm…  Seems kind of obvious, that.  I rather favour that as the likely explanation.

There are actually multiple hypotheses that could have come out of the Seven Countries Study.  Maybe the culprit was indeed saturated fat.  Maybe it was animal fat.  Maybe it was animal protein.  Maybe it was industrialization and processed foods.  Maybe it was total protein.  Maybe it was carbohydrate.  All of these hypotheses could have been generated from the same study.  But what we got was the Diet-Heart Hypothesis.

To some extent, this has persisted to this date.  Most people still believe in the Diet-Heart Hypothesis as laid out originally in 1970.  The Lipid hypothesis refers to the hypothesis that serum cholesterol causes heart disease.  The Diet-Heart hypothesis refers to the hypothesis that dietary saturated fat raises cholesterol and therefore raises heart disease.  There are actually problems with all parts of this hypothesis.

The first problem faced was the fact that total serum cholesterol turned out not to be correlated to heart disease at all.

There was very weak correlation with death and total cholesterol.  In fact, in the oldest age groups, high cholesterol was strongly protective.  This was shown in multiple other studies.  Total cholesterol was not very good at all.  This problem was solved by looking at the ‘good’ cholesterol HDL versus the ‘bad’ cholesterol LDL.  This seemed to fix things up a bit better.

If anything, there was a stronger correlation between low HDL and heart disease than LDL.  The dietary manipulations tended to move both HDL and LDL up or down rather than individually.  Drugs, such as torcetrapib were developed at massive expense to raise HDL levels.  Unfortunately, these drugs all killed people and were abandoned.  Pfizer spend close to $1 billion dollars to develop this drug all based on the same faulty correlation data.  Soon afterwards, thousands of people were laid off.  Low HDL did not cause coronary disease, it was only a marker for the disease.

Looking back, it all seems so obvious.  Exercising raises HDL.  Maybe people who exercised had both higher HDL and lower heart disease.  Increased olive oil increases HDL.  Maybe olive oil both raises HDL and lowers heart disease.  Stopping smoking raises HDL.  Maybe stopping smoking both raises HDL and lowers heart disease.  This emphasizes again the danger of correlation studies.

Nevetheless, scientists moved forward trying to prove that dietary saturated fat increased cholesterol levels.  The Framingham studies were the ideal place to look.

In 1948, Harvard University decided to undertake extensive testing in Framingham, Mass.  The bloodwork and dietary habits of an entire community would be monitored over decades to learn about the risk factors of heart disease.  Every 2 years, all residents would undergo screening with bloodwork and questionnaires.  By comparing those that developed heart disease and those that did not, they hoped to learn the factors that were important.

In the early 1960s, after massive human effort and expenditure the results of the Framingham Diet Study were available.  Hoping to find a definitive link between saturated fat intake, serum cholesterol and heart disease.  Instead what they found was no such thing at all.  Nada.  Nothing.  There was absolutely no correlation.  So they did what all researchers the world over do.  They buried the result.  Ignore the result and pretend the study never existed.

Dr. Michael Eades, writing on his blog, was able to find an old copy and peruse the results.  From his copy, he notes that the report states:

There is no indication of a relationship between dietary cholesterol and serum cholesterol level.

At least this part is consistent.  Dr. Ancel Keys noted much the same thing.  Physiology also backs up the fact that most of the cholesterol in our bodies is made by our own livers.

Even today, the National Cholesterol Education Program (NCEP) states:

Dietary cholesterol causes marked hypercholesterolemia in many laboratory animals, including nonhuman primates. High intakes of cholesterol in humans, however, do not cause such a marked increase in serum cholesterol

Translation – Non human primates should DEFINITELY avoid dietary cholesterol.  Humans, though, not so much.

Regarding fat:

No association between percent of calories from fat and serum cholesterol level was shown; nor between ratio of plant fat to animal fat intake and serum cholesterol level.

Remember that original studies also showed no association of total fat and cholesterol.  It was only saturated fat that made a difference.  However, here, unlike the Seven Countries Study, animal versus plant fat made no difference.

The most important part is the relationship with heart disease.  Here’s the final conclusions of this forgotten jewel:

There is, in short, no suggestion of any relation between diet and the subsequent development of CHD in the study group

Yeah.  There was basically no relationship between diet and heart disease.  So much for the Diet-Heart Hypothesis.  This should have been the study to bury this mistaken hypothesis.  Instead, researchers chose to bury the study instead.  They condemned us to 40 years of a low fat future that included an epidemic of diabetes and obesity.

What is really sad is the news commentary by Dr. William Kannel, the director of the Framingham Heart Study.  He states that, just because his own study proved that diet has no connection with cholesterol, “it is incorrect to interpret this finding to mean that diet has no connection with blood cholesterol,”.  Dude – you makin’ no sense.

Over the next half century, no matter how hard we looked, there was no relationship between dietary fat and serum cholesterol.  Other studies, such as the Tecumseh study, continued to find no discernible relationship.  Even the National Cholesterol Education Program admits that “Dietary cholesterol causes marked hypercholesterolemia in many laboratory animals, including nonhuman primates. High intakes of cholesterol in humans, however, do not cause such a marked increase in serum cholesterol”

So non human primates should DEFINITELY avoid dietary cholesterol.  Humans, though, not so much.

Continue to Trans Fat – Hormonal Obesity XXXVI

Start here with Calories I – How Do We Gain Weight?

See the entire lecture – The Aetiology of Obesity 6/6 – Fat Phobia

2018-05-26T08:39:10+00:0011 Comments

About the Author:

Dr. Fung is a Toronto based kidney specialist, having graduated from the University of Toronto and finishing his medical specialty at the University of California, Los Angeles in 2001. He is the author of the bestsellers ‘The Obesity Code’ and ‘The Complete Guide to Fasting’. He has pioneered the use of therapeutic fasting for weight loss and type 2 diabetes reversal in his IDM clinic.

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Scott Wang
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Scott Wang

Dear Dr. Fung, I’ve found the original NCEP report, the link is listed below http://circ.ahajournals.org/content/106/25/3253.full In the text, the report did state that dietary cholesterol does not markedly raise serum cholesterol level. However, the report also states “On average, the response of serum cholesterol to dietary cholesterol as revealed in tightly controlled studies is approximately 10 mg/dL per 100 mg dietary cholesterol per 1000 kcal.” In the final paragraphs the report suggested “Less than 200 mg per day of cholesterol should be consumed in the TLC Diet” This is a kind of confusing, since dietary cholesterol does not raise serum… Read more »

kfacwpup
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I agree with you. Even in the original Seven Countries Study by Dr. Ancel Keys which started the low fat trend, there was no correlation between dietary cholesterol and serum cholesterol. So why we should decrease dietary cholesterol is certainly a mystery to me. I don’t advise reducing dietary cholesterol at all.

Mary
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Mary

statin question… Why are diabetics suppose to take statins since researchers are thinking that the reason they cause diabetes after long term use is interference with insulin sensitivity and perhaps cause insulin resistance. It seems counter productive to change one’s diet to increase sensitivity while taking a statin that decreases it… All supposedly to reduce cvd when diabetes leads to high cvd deaths. Seems like a strange proposition with little pay off.. Let alone what is in this blog entry above. What are your thoughts on diabetics who are doing the LCHF/fasting taking statins for high cholesterol?

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[…] might (mistakenly) think that decreasing dietary cholesterol may reduce blood cholesterol levels. However, 80% of the cholesterol in our blood is generated by the liver, so reducing dietary […]

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[…] פוסט זה מוגש כשירות לציבור. הזכויות על התוכן שייכות לכותב של הפוסט המקורי. את הפוסט המקורי ניתן למצוא בכתובת הזאת. […]

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[…] פוסט זה מוגש כשירות לציבור. הזכויות על התוכן שייכות לכותב של הפוסט המקורי. את הפוסט המקורי ניתן למצוא בכתובת הזאת. […]

bachcole
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bachcole

And people wonder why I rage at con med. Perhaps it would be more productive if I raged at people for worshiping at the altar of modern medicine.

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[…] would lead to high blood levels. This was disproven decades ago. One might (mistakenly) think that decreasing dietary cholesterol may reduce blood cholesterol levels. However, 80% of the cholesterol in our blood is generated by the liver, so reducing dietary […]

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[…] would lead to high blood levels. This was disproven decades ago. One might (mistakenly) think that decreasing dietary cholesterol may reduce blood cholesterol levels. However, 80% of the cholesterol in our blood is generated by the liver, so reducing dietary […]

Mike Armishaw
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Mike Armishaw

Firstly I’d like to say that this series of posts are some of the most interesting and enlightening that I have read. But I am a bit concerned about this statement – “There is nothing more dangerous in medicine than the correlation study. It cannot be used to prove a hypothesis, only to disprove one.” I absolutely agree that correlation studies can’t be used to prove a hypothesis, but surely they also can’t be used to disprove one. If correlation is no proof of causation then surely lack of correlation is also no proof of lack of causation. It could… Read more »