Dietary Fats and Heart Disease – Exposing the Villain

“I would only argue that Senators don’t have the luxury that the research scientist does, of waiting until every last shred of evidence is in.”

These words were spoken by Senator George McGovern 35 years ago when confronted by Dr. Robert Olson from St. Louis University. Senator McGovern’s Select Committee on Nutrition and Human Needs went ahead and published their famous report, “Dietary goals for the United States” in 1977.

Fat and heart disease - exposing the villain

Doctor Olson, however had pleaded for “more research on the problem before making announcements to the American public”. The main message from the McGovern report was to reduce overall fat consumption, reduce the consumption of saturated fat and cholesterol, and to substitute polyunsaturated fatty acids (PUFA) for saturated fat. Decreased consumption of meat, butterfat, eggs and other high cholesterol sources was recommended. McGovern’s words reflect the fact that the report was not based on strong scientific data.

The committee’s members acknowledged that their recommendations relied on epidemiological and observational data at best. There were no prospective randomized studies available to support their recommendations.

Dr. D.M. Hegsted, professor of nutrition at Harvard School of Public Health, who assisted in the preparation of the report wrote: “The question to be asked, therefore, is not why should we change our diet but why not. What are the risks associated with eating less meat, less fat, less saturated fat, less cholesterol, less sugar, less salt and more fruits, vegetables, unsaturated fat and cereal products – especially whole grain cereals. There are none that can be identified and important benefits can be expected”.

What the committee’s members probably did not realize however, was that their report laid the foundation for worldwide dietary guidelines for the next 35 years. Ever since , “eat less saturated fat and cholesterol…” , has been the cornerstone recommendation from medical professionals, for patients with heart disease or those who want to reduce their risk of heart attack.

Although the McGovern committee’s report turned out to be  influential, several other important expert panels had already provided similar recommendations. The advise  to limit saturated fats was already alive in the 1950s. In 1957 the American Heart Association suggested that a decreased consumption of saturated fats might reduce  the risk of heart disease.

The Inter-Society Commission for Heart Disease Resources and The American Heart Association had already in the early 1970s suggested a reduction in dietary cholesterol to less than 300 mg a day.

However, the experts did not agree. In October 1977, the Canadian Department of National Health and Welfare concluded that: “Evidence is mounting that dietary cholesterol may not be  important to the great majority of people… Thus a diet restricted in cholesterol would not be necessary for the general population”.

But  the wheels were turning fas, and food manufacturers were already adopting new strategies. Low-fat food varieties of all possible kinds spread throughout the world. Butter consumption decreased, and vegetable oils became popular. Cholesterol and saturated fat were to be  eliminated from our dishes. The villains had been exposed  and had to be  taken care of.

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Trans Fat Joins the Villains

The French scientist Paul Sabatier developed the hydrogenation process in the 1890s. In 1902, Wilhelm Normann found that liquid oils could be hydrogenated to form trans fatty acids. This turned out to be the first man made fat.

During the second world war, the use of trans fats rose because of the increased use of margarine. In the early 1980s there was a strong campaign by consumer advocacy groups against using saturated fat for frying in fast-food restaurants. In response, most fast-food companies began using partially hydrogenated oils containing trans  fat instead of beef tallow and tropical oils high in saturated fats.

A lot of evidence indicates that the fear of saturated fats during the 1950s through the 1980s, lead to an increased use of trans fats.

In the 1990s it became clear however that trans fats might be harmful. Numerous research studies during the 1990’s revealed correlations between trans fatty acids and increased LDL-cholesterol and a higher incidence of heart disease.

In 1993 health advocacy groups started calling for fast-food restaurants to stop using partially hydrogenated oils in their deep fryers. Trans fat was the new villain.

In 2003, Denmark was the first country in the world to limit the use of trans fats by law. Trans fat labeling became mandatory in the United States in 2006. The same year, The American Heart Association became the first major health organization to specify a daily limit:  less than 1 percent of calories from trans fat. Later in the year, New York became the first U.S. city to pass a regulation limiting trans fat in restaurants.  Multiple cities and states have since proposed similar regulations.

Is Polyunsaturated Fat (PUFA) a Healthier Option than Saturated Fat?

The recommendation to substitute PUFA for saturated fat was one of the main goals of the McGovern report in 1977.

This probably originated from the research of the influential Minnesota epidemiologist, Ancel Keys. Keys is often acknowledged as the father of the diet-heart hypothesis. He published many studies in the 1960′, and 70’s demonstrating higher cholesterol levels among patients with heart disease. His studies also showed higher cholesterol levels among people who consumed food rich in saturated fat and cholesterol.

From his famous “Seven Countries Study” Keys concluded that dietary fat was the single most important cause of heart disease because it elevates blood cholesterol. However, the study has been criticized for the method in which populations were selected for the study, and the way that the population (ecologic) correlations were carried out. Keys believed, like so many others, that a Mediterranean-style diet low in animal fat and rich in PUFA protected against heart disease.

Advice to replace animal fats rich in saturated fats by vegetable oils rich in PUFA  has been a cornerstone of worldwide dietary guidelines for half a century.

However, when the advice originated fifty years ago, PUFAs were regarded as single molecular category with one highly relevant biological effect – to reduce blood levels of cholesterol. At that time, omega-6 (linoleic acid) was the best known PUFA. Since then, it has been recognized that PUFAs comprise multiple species of omega-3 and omega 6, each with unique biochemical properties, and perhaps different cardiovascular effects.

What was the evidence behind recommending decreased consumption of saturated fat and increased consumption of PUFA?

Interestingly, there were three prospective studies performed during the 1960’s and 70’s comparing the effects of these two types of fats. The studies involving a total of 1300 men with heart disease in England, Norway, and Australia used diets with high ratios of PUFAs  to saturated fats, limited dietary cholesterol, and low levels of monounsaturated fat.

The trials lasted five years, and despite achieving lower cholesterol levels, people on the experimental diet did not do any better than their counterparts did on the control diet. Therefore, these studies did not support the hypothesis that substituting PUFA for saturated fat was beneficial. Somehow, the medical community did not seem to take notice. Interestingly, one of these studies, The Sydney Diet Heart Study was recently recovered, reevaluated and published in the British Medical Journal. The results have received huge attention.

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Linoleic Acid (Omega – 6) –  The New Villain

Fat and heart disease - exposing the villain

The Sidney Diet Heart Study was a randomized trial conducted from 1966 – 1973. It tested the effect of replacing saturated fat with linoleic acid (omega-6) from safflower oil.

Safflower oil is a concentrated source of linoleic acid, containing no other PUFAs. The study population consisted of 458 men aged 30-59 years with a recent history of heart attack (acute myocardial infarction or acute coronary insufficiency). The men were randomized to an intervention group (n=221) and a control group (n=237).

The intervention group received instruction to increase their PUFA  intake to about 15% of food energy, and to reduce their intake of saturated fat and dietary cholesterol to less than 10% of food energy and 300 mg per day, respectively.

To achieve these targets, intervention participants were provided with liquid safflower oil and safflower oil polyunsaturated margarine (“Miracle” brand, Marrickville Margarine). Liquid safflower oil was substituted for animal fats, common margarines, and shortenings in cooking oils, salad dressings, baked goods, and other products, and was also taken as a supplement. Safflower oil polyunsaturated margarine was used in place of butter and common margarine. The control group received no specific dietary instruction. However, some participants began substituting polyunsaturated margarine for butter after their coronary event.

The results of the study were quite striking. Compared with the control group, the intervention group had an increased risk of all-cause mortality (17.6% vs. 11.8%),  cardiovascular mortality (17.2% vs. 11.0%) and mortality from coronary heart disease (15.3% vs. 10.1%). This difference existed despite the fact that total serum cholesterol decreased more in the intervention group than in the control group (13.3% vs. 5.5%).

These unfavorable effects of omega-6 are consistent with two other randomized controlled trials, in which saturated fats were replaced  with omega-6 and common margarines were replaced  with corn oil.

By reanalyzing  the original Sidney Diet Heart Study data, the authors were able to include the study into their previous  meta-analysis. The meta-analysis  covers secondary prevention studies where saturated  fats were replaced, either by omega-6 selective PUFA  interventions or a combination of omega-6 and omega-3.

In short; replacing saturated fats with PUFAs containing mainly omega-6 fatty acids appears to increase coronary heart disease mortality, while replacing saturated fats with a combination of omega-3 and omega-6 decreases coronary heart disease mortality. This may explain why a diet rich in omega-3, such as the Mediterranean diet appears to positively affect the risk of heart disease.

Omega-6 is the most abundant fatty acid in low-density lipoprotein (LDL) particles. Oxidized linoleic acid metabolites (OXLAMs) are the most abundant oxidized fatty acids in oxidized LDL. The authors of the British Medical Journal paper suggest that a diet-induced increase in the production of bioactive OXLAMs may contribute to atherosclerosis and cardiovascular disease pathogenesis. This hypothesis supports the possibility that atherosclerosis may occur through mechanisms that are very distantly related to plasma cholesterol.

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Is It All Due to the Trans Fats?

Australia’s National Heart Foundation has claimed the recent Sidney Diet Heart Study is misguided. Dr Robert Grenfell who is National Health Director at the Heart Foundation points out that “in the 60s and 70s margarine still contained trans fats which we now know are extremely harmful to heart health. Replacing saturated fat with a product that was high in trans fat would never be recommended now.”

Bill Shrapnel, the Deputy Chairman of the Sidney University Nutrition Research Foundation agrees that “the study was not objective because margarine no longer contains the trans fatty acids it did at the time of the trials”. He adds: When the study began, Miracle margarine contained approximately 15 per cent trans fatty acids which have the worst effect on heart disease risk of any fat. The adverse effects of the intervention in this study was almost certainly due to the increase in trans fatty acids in the diet.”

The authors of the recent British Medical Journal article have a completely different view on the trans fat issue. In their discussion of the results they point out that the trans fatty acid content of the participant’s diets was not recorded. On the other hand they argue that the restriction of common margarines and shortenings (major sources of trans fatty acids) in the intervention group would be expected to substantially reduce consumption of trans fatty acids compared with the control group.

Thus, the consumption of trans fatty acids may indeed have been higher among the control patients than the intervention patients. Trans fatty acids are known to raise cholesterol levels. The fact that cholesterol levels decreased more in the intervention group than in the control group does not indicate that the intervention group had more trans fatty acids in their diet.

Dietary Fats and Heart Disease – Exposing the Villain

When it comes to crime novel, Agatha Christie is the master of twists and turns. You never know until the last page who is the villain. In one chapter you are led to believe it was the gardener or the butler. In the next chapter you definitively suspect the beautiful widow. The two things you could be certain of was that there were always going to be more twists and turns, and the end would take you by surprise. I somehow have a similar feeling about fat and heart disease. There will be  more twists and turns before we know the truth. For the time being though, it appears that the doomed outlaw, saturated fat may not be the worst villain. Indeed, the evidence against it is fairly weak.

At least, saturated fat appears more innocent than trans fat and omega-6.   I wonder, could Ancel Keys have been studying an effect of trans fat instead of saturated fat in his epidemiological research. Since he never separated these two, we will probably never know.

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Hildur Tómasdóttir
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Hildur Tómasdóttir

Good rewiev Axel. Keep up the good work

Richard
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Richard

Doc, it’s rather unfortunate that you do even bother to conduct decent investigation. This reminds of Richard Dawkins who diclosed how sad it is that the creationist do not posses even the rudimentary information over the topic they so much criticize. Think about it, if you read the last page of a novel would you have any clue what actually happened? The holy nonsense manthra and new gospel is that Ancel Keys cherry picked the data. The skeptics cannot even tell the difference between a data set produced by the F.A.O and mortality statistics of WHO which Keys compared in… Read more »

Axel F Sigurdsson
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Axel F Sigurdsson

@Richard. Thanks for sharing your thoughts. I admire your interest and knowledge on the subject. Your opinion is indeed shared by many of my colleagues. I have looked into the links you provided, they´re interesting. In fact I found the Keys story very intriguing. I have huge respect for Ancel Keys and his research. It is a misinterpretation if you believe it was my intention to discredit him in any way. Regarding your words “You went deep on the nonsense while claiming that the seven countries reported that dietary fat per se was deemed as bad”: These were not my… Read more »

JustMEinT Musings
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LDL is the villain? but LDL as an entity or LDL particle size specifically?
Great article as always Doc I do appreciate your writings
Clare in Tasmania

davebrown9
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davebrown9

Actually, saturated fats have little effect on cholesterol levels compared to other dietary factors. Excerpt: A diet rich in foods with proven heart-healthy benefits is significantly better than a diet low in saturated fat for reducing LDL-cholesterol levels in patients with hyperlipidemia, according to the results of a new study [1]. The “dietary portfolio” of cholesterol-lowering foods reduced LDL-cholesterol levels by 26 mg/dL, nearly as large a reduction as was observed in some of the earliest statin trials, according to researchers. https://www.theheart.org/article/1267163.do Research also indicates that lowering total and LDL cholesterol may be problematic for preserving muscle mass. Excerpt from… Read more »

Richard
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Richard

Davebrown, The first study you quoted was that by Jenkins. The diet he prescribed was a vegan diet with soy-products and canola margharine. Not really something I see promoted by the low-carb echo-chamber. Yes, his diet worked better that the “low-saturated” fat diet that is commonly prescribed in hospitals and which includes plenty of animal protein. Although, the Jenkins diet did not work as well as Ornish low-fat vegan diet which has been documented to produce 40% drops in LDL cholesterol in just 12-weeks. This is equivalent to high-dose statin theraphy. Rural-Central Africans are one of the most musculus people… Read more »

Richard
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Richard

Doc, In regards to the Sydney-trial; the TC cholesterol in the intervention arm after the 12-month follow-up was 6.3mmol/ (vs. 6.9 among the controls). No additional information was provided. The cholesterol levels, despite being lower in the intervention, was way enough what is required to keep up the disease process going at a full pace. I think professor Peter Clifton provided very informative insights; This is a very small study with only 63 total deaths. The 5.8% difference between groups for total mortality represents a difference of 10 deaths between groups (p=0.051) computed from the % deaths which does not… Read more »

bhrdoc
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An excellent review Axel. Two additional points: Ancel Keys followed the Mediterranean Diet and lived to be almost 101 years old. In addition, the Lyon Diet Heart Trial achieved significant reductions in total mortality, CV mortality and recurrent MI in heart attack survivors randomized to the Western “prudent” diet or the Mediterranean Diet despite levels of LDL-cholesterol far above current guidelines (4.23 mmol/L in controls versus 4.17 mmol/L in Mediterranean Diet). It’s important to emphasize that IT’S NOT ALL ABOUT THE LDL!

Axel F Sigurdsson
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Axel F Sigurdsson

@bhrdoc. Thanks Barbara. I agree with you on the Mediterranean diet. If there was a “heart healthy diet” contest I would definitively vote for the Mediterranean diet. It emphasizes healthy fats (PUFAs with high proportion of omega-3) and healthy carbohydrates, lots of fish, not to much red meat, lots of vegetable. Recent studies also show that this diet is also one of the best choices for type-2 diabetics.

Jeffry N. Gerber, M.D.
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Axel – Thanks for this great summary. There is another great site from your part of the world – https://authoritynutrition.com I do hope to visit someday – Dr Jeff

Axel F Sigurdsson
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Axel F Sigurdsson

@ Jeffry. Thanks Jeff. Actually me and Kris at Authority Nutrition keep on touch all the time. Iceland is a small country and we have common interests. Kris knows more than anybody about the secrets of the internet, so I try to get advice from him when I can.

davebrown9
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davebrown9

Few seem to realize that any dietary change that reduces omega-6 intake furnishes at least some protection from heart disease and other chronic inflammatory conditions. Most Paleo enthusiasts know to stop consuming industrial seed oils and replace them with traditional fats such as butter, lard, beef tallow, and coconut oil. Low-fat enthusiasts accomplish much the same thing. By restricting total fat intake, they inadvertently reduce their daily intake of omega-6s. An intermediate approach is the Mediterranean diet which is high in omega-9 monounsaturated fatty acids. Here’s an excerpt from an 2009 article about Dietary fat quality and heart disease. “The… Read more »

js290
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js290

Dr. Mary Enig points out that it was the CSPI that “forced” restaurants to switch from natural saturated fats to trans fats proclaiming its safety. Then, they lobbied to against the use of trans fats when the safety evidence mounted against. It may instructive to point out that fatty acids supply more ATP than glucose. “The oxidation of fatty acids yields significantly more energy per carbon atom than does the oxidation of carbohydrates. The net result of the oxidation of one mole of oleic acid (an 18-carbon fatty acid) will be 146 moles of ATP (2 mole equivalents are used… Read more »

Richard
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Richard

@BHRDOC CV mortality and recurrent MI in heart attack survivors randomized to the Western “prudent” diet or the Mediterranean Diet despite levels of LDL-cholesterol far above current guidelines (4.23 mmol/L in controls versus 4.17 mmol/L in Mediterranean Diet). It’s important to emphasize that IT’S NOT ALL ABOUT THE LDL! I see the role of cholesterol to CHD in terms of the so-called causal exposure model (Sniderman et al 2012). Against this background, the above comments seem somewhat odd to me. I have three particular problems with this line of reasoning! 1) Age; Lyon was a secondary prevention made-up of old… Read more »

Healthy Longevity
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Similar to Richard’s opinion I feel that this article is misleading. By the time of the McGovern report in 1977 there was much more data than just “epidemiological and observational data”. By 1977 there were dozens of rigorously controlled metabolic ward experiments clearly demonstrating that dietary cholesterol and saturated fat elevate serum cholesterol. Furthermore most of the 17 diet and drug trials included in Sir Richard Peto’s meta-analysis presented at the 1984 NIH consensus (published previously in 1981) had already been published by 1977. Peto demonstrated that pooling either the diet or drug trials that successfully lowered serum cholesterol resulted… Read more »

George Henderson
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George Henderson

The bottom line is, that whether LA or TFA was killing people in Sydney, the patients were using this product because of faith in the lipid hypothesis. @richard has many good arguments but none explains the lack of correlation between SFA and CHD or total mortality. Most recently in Finland with very high upper intake (KIHD). EFAs are essential nutrients so of course they are protective in proper amounts and ratios, but they can replace bread as well as butter to get this effect, and it seems to plateau at around 5%E, not 15%. You need to look at all-cause… Read more »

muscle supplement
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Brian Scott Edwards
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Brian Scott Edwards

Excellent writing. I am confused by the statement, “Trans fatty acids are known to raise cholesterol levels. The fact that
cholesterol levels decreased more in the intervention group than in the
control group does not indicate that the intervention group had more
trans fatty acids in their diet”

Someday we will not use the term “cholesterol”. LDLc is very different from LDLp or apo B. More HDLc increases total cholesterol. However it may be HDLp that is more important. Trying to form policy even today on poor lab data.

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