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This article in The Guardian alleges that the nutritional science establishment has spent the last 4 decades claiming that fatty diets cause heart disease when in fact sugar is largely to blame. The article presents this as a case of eminence-based medicine and groupthink.

There are a lot of claims in the article, but I'd like to ask about the main one: that historic increases in heart disease were caused by population-wide increases in dietary sugar and not increases in dietary fat.

Update: This article in the Washington Post tells a similar story.

  • I have to wonder about the claim that sugar was ignored. Certainly its 'badness' was known in some parts of popular culture from the 1970s. Witness these song lyrics: "I don't eat white flour; white sugar makes you rot Oh, white could be beautiful but mostly it's not" (Melanie Safka: "I Don't Eat Animals") And I'm close to certain that things like deep-fried turkey weren't common in those days. – jamesqf Apr 9 '16 at 20:23
  • I'm closing this reluctantly, and I hope we can fix it and re-open it because I am interested in the answer. It is a long article, and there is too much opportunity to tackle strawmen rather than real arguments. I want to quote the claim in the article that says high-fat diets cause/don't cause obesity. I am seeing claims about heart-disease, cholesterol, and cancer, but I am having trouble finding anyone in the article (more recently than the 70's) saying high-fat diets don't cause obesity. Maybe we need a different source? Perhaps I am missing it; it is a long article. – Oddthinking Apr 10 '16 at 12:46
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    I also want to avoid the confusion we often seem to get: If a high-calorie diet is a cause of weight gain, and sugar and fat are both high in calories, then it is true that someone on a high-fat diets could gain weight, and also true that someone on a low-fat diet could also gain weight. – Oddthinking Apr 10 '16 at 12:55
  • @Oddthinking: I've updated the question to ask about heart disease rather than obesity (I was mistakenly conflating them). Hopefully it is now clearer and fit to be answered. – Paul Johnson Apr 10 '16 at 13:28
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    @oddthinking The issue is more with dietary advice than diets. The advice to eat less fat seemed to lead to more obesity rather than less. Possibly because diets high in fat satiate the body faster (so people eat less in total on high fat diets) but carbohydrate doesn't so people eat more. Assuming that the amount eaten is constant regardless of the mix of calorie sources seems to be wrong. Moreover, the quality of many studies of the actual diet seem to be poor so it is hard to remove confounding factors like sugar from the old work that led to the mainstream advice. – matt_black Apr 10 '16 at 16:12
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+100

All fats do not have the same effect on the body when ingested even though they possess a similar chemical structure.

All fats have a similar chemical structure: a chain of carbon atoms bonded to hydrogen atoms. What makes one fat different from another is the length and shape of the carbon chain and the number of hydrogen atoms connected to the carbon atoms. Seemingly slight differences in structure translate into crucial differences in form and function. Source: The truth about fats

Fat from food provides energy, needed for building cell and nerve structures and also helps in absorption of some vitamins and minerals. It is essential for clotting of blood, movement of muscle, and inflammation.

The American Heart Association (AHA) recommends that between 25 and 35 percent of your total calories come from fat, and the U.S. Department of Agriculture's Dietary Guidelines for Americans recommend a range of 20 to 35 percent. Source: All Fats Are Not Created Equal

Evidence on the relation between fat and heart disease:

  1. Low-fat diets tend to have no effect on cardiovascular disease.

Based on this evidence, the 2015 Dietary Guidelines Advisory Committee concluded that low-fat diets have no effect on CVD and emphasized the importance of healthful, food-based diet patterns.

Based on this evidence, the 2015 Dietary Guidelines Advisory Committee stated, for the first time, that dietary guidelines should not focus on lowering total fat. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

  1. Restriction on total fat indirectly leads people to consume large amounts of refined carbohydrates containing starch and added sugar.

The current restriction on total fat shapes numerous government feeding programs and policies; drives industry marketing of fat-reduced desserts, snacks, salad dressings, processed meats, and low-fat other products of poor nutritional value; and leads most Americans to actively avoid dietary fat and instead consume far too many refined carbohydrates. Avoidance of total fat also undermines attempts to limit refined starch and added sugar, while discouraging the food industry from providing products higher in healthful fats. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

  1. Evidence for monounsaturated fat (oleic acid) to be considered as a cardioprotective fat is mixed and focusing on specific types of foods and oils is advised as better against selecting foods only based on their monounsaturated fat content.

The current evidence for cardiometabolic benefits of total monounsaturated fat (largely oleic acid) is not strong. These results suggest that other compounds in these fats/oils may modify the overall health effects. Thus, focusing on specific types of foods and oils, rather than monounsaturated fat content per se, may be most prudent. Extra virgin olive oil and mixed nuts, and perhaps high-oleic canola oil, appear to be good dietary choices to improve cardiometabolic health. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

Research also shows that there is no other benefit of replacing saturated fat with vegetable oils rich in linoleic acid apart from lowering serum cholesterol and this lowering does not relate to a lower risk of death from coronary heart disease.

Available evidence from randomized controlled trials shows that replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes. Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid. Source: Re-evaluation of the traditional diet-heart hypothesis

  1. Cardiometabolic effects of polyunsaturated fats such as seafood-derived n-3 fats is well documented.

The cumulative evidence from observational studies, clinical trials, and controlled interventional studies continues to favor plausible cardiovascular benefits of modest dietary fish consumption, in particular for the endpoint of CHD death. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

Consumption of polyunsaturated fat-rich vegetable oils is advised for lowering risk of coronary heart disease.

Increased consumption of polyunsaturated fat-rich vegetable oils is an evidence-based strategy to lower CHD risk, whether in place of saturated fat or carbohydrate. Optimally, polyunsaturated fat-rich vegetable oils should perhaps replace refined starches and added sugars, given the independent harms of these refined carbohydrates. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

  1. Higher trans fatty acids (TFAs) intake from partially hydrogenated oils is known to be associated with the risk of coronary heart disease and sudden death.

In sum, the implicated pathways suggest that TFA-containing partially hydrogenated oils influence pathways related to adipocyte dysfunction and insulin resistance. Emerging evidence suggests that 18:2 TFA isomers may be the most adverse; these can be formed through not only partial hydrogenation, but also other industrial processes such as oil deodorization and high-temperature cooking.380,381 Because partially hydrogenated oils are food additives with clear adverse effects, their elimination is a public health priority. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

Evidence on the relation between sugar and heart disease:

  1. Refined grains/grain products, sugar sweetened beverages, sweets and starch (certain potatoes) all produce brisk rises in blood glucose and insulin and may induce multiple adverse effects including cardiovascular disease.

In addition to direct harms, low-quality carbohydrates such as refined grains, certain potatoes, sugar-sweetened beverages (SSBs), and sweets may increase cardiometabolic risk by displacing other, healthier foods in the diet, eg, fruits, vegetables, nuts, legumes, and minimally processed whole grains. Consistent with this constellation of adverse effects, poor-quality carbohydrates are associated with long-term weight gain, diabetes mellitus, and CVD. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

  1. The 2015 Dietary Guidelines Advisory Committee advised that the “consumption of ‘low-fat’ or ‘nonfat’ products with high amounts of refined grains and added sugars should be discouraged".

Based on their adverse effects and pervasiveness in modern diets, reducing refined grains, starches, and added sugars is a major dietary priority for cardiometabolic health. Although SSB intake is declining in the United States, intakes of added sugars in other foods and, even more so, of refined grains continue to represent a major part of the diet. Currently, nearly 3 in 4 Americans consume too many refined grain products. Indeed, many people seek out these products, erroneously believing they are beneficial based on their promotion as low-fat or fat-free foods. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

Summary:

  1. TL;DR: Not all fats are created equal and the level of intake is the key to reducing adverse outcomes such as cardiovascular disease. Research into fat diets still advise that intake of saturated fats and unsaturated fats should be moderate in order to benefit the heart and to completely avoid or reduce foods high in transfat.

Polyunsaturated fats were shown to be fairly neutral in terms of heart health in recent research. These fats, which are in foods such as salmon and canola oil, were neither good nor bad, but “trending toward favorable,” Dr. Nissen says. Oils rich in polyunsaturated fats also provide essential fats that your body needs but can’t produce itself — such as omega-6 and omega-3 fatty acids.

Monounsaturated fats provide the most health benefit, according to research, and are an important component of the heart-healthy Mediterranean diet, Dr. Nissen says. They are found in foods such as olive oil and sesame oil and in nuts such as almonds or walnuts. Source: You Can Eat Fat If You Choose Wisely

Recent research evidence suggests some benefits of including saturated fat such as dairy fat or high-fat dairy foods such as cheese in diet. However, these recommendations are based more on the influences of fermentation/probiotics, calcium and vitamin D contents rather than their complete cardiometabolic effects. The American Heart Association (AHA) advises to keep the intake of saturated fats less than 7 percent of total daily calories.

The current science supports consuming more yogurt and possibly cheese; with the choice between low-fat versus whole-fat being personal preference, pending further investigation. This new evidence also calls for substantial further investment in research on cardiometabolic effects of dairy foods, including relevant components and molecular mechanisms. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

A beneficial diet should have restriction in foods high in trans fat.

A maximally beneficial diet pattern should concurrently emphasize reductions in refined (not all) carbohydrates, processed meats, and foods high in sodium and trans fat; moderation in unprocessed red meats, poultry, eggs, and milk; and high intakes of fruits, nuts, fish, vegetables (excluding russet/white potatoes), vegetable oils, minimally processed whole grains, legumes, and yogurt. Source: Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

  1. More research is needed for authoritatively determining the connection between high dietary fat and its effect on heart diseases.

Although multiple factors have contributed to this decline, none of the other factors can explain this huge improvement in health, and the replacement of saturated fat with polyunsaturated fat (both n-6 and n-3 fatty acids) is almost certainly a major, probably most important, factor. Reversing these changes would almost certainly result in great harm. Source: Old data on dietary fats in context with current recommendations

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    You quote a wide range of research, and then conclude more is required. What is your basis for deciding that, and not that the research is in? – Oddthinking Apr 15 '16 at 14:26
  • Had based these comments to mirror the opinion of a nutrition expert Dr. Walter Willett who had commented on the findings of Ramsden et al. paper in the British Medical Journal which challenged the benefits of replacing saturated fat with polyunsaturated fat and its effects on cardiac health (referenced in summary). He further states that "Notably, since the 1960’s, the US diet has changed in this way; intake of linoleic acid has approximately doubled, and this has corresponded to a greater than 60 percent decline in coronary heart disease mortality". – pericles316 Apr 16 '16 at 3:34
  • @Oddthinking-Then what about this? "The current science supports consuming more yogurt and possibly cheese; with the choice between low-fat versus whole-fat being personal preference, pending further investigation. This new evidence also calls for substantial further investment in research on cardiometabolic effects of dairy foods, including relevant components and molecular mechanisms." – pericles316 Apr 16 '16 at 4:25
  • That's dairy foods, rather than diets high in fat. E.g. The same source recommends vegetable oils, and avoiding trans-fats. – Oddthinking Apr 16 '16 at 6:38
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    @Oddthinking-Changed the classification of dairy fat to monounsaturated fat and explained accordingly. – pericles316 Apr 16 '16 at 8:14

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