Diets low in saturated fat may not curb heart disease risk or increase longevity, according to a leading US cardiovascular research scientist and doctor of pharmacy.

Dr James DiNicolantonio made the claims in an editorial published in the open access journal Open Heart, saying that current dietary advice to replace saturated fats with carbohydrates or omega 6-rich polyunsaturated fats was based on “flawed and incomplete data from the 1950s”.

Dietary guidelines should be “urgently reviewed and the vilification of saturated fats stopped to save lives”, Dr DiNicolantonio insisted.

Dr DiNicolantonio argued that the “demonisation” of saturated fats dated back to 1952, when research suggested a link between high dietary saturated fat intake and deaths from heart disease. But Dr DiNicolantonio said the author of the 1952 paper drew his conclusions on data from six countries and ignored data from a further 16, which did not fit with his hypothesis. According to Dr DiNicolantonio, subsequent analysis of all 22 countries’ data disproved the claims about saturated fat and heart health.

This study prompted the belief that since saturated fats increased total cholesterol — which Dr DiNicolantonio said was a “flawed theory in itself” — they must also increase heart disease risk. As well, as foodstuffs with the highest calorie density, the thinking was that reduced saturated fat intake would naturally curb obesity, diabetes and metabolic syndrome. But Dr DiNicolantonio said mounting evidence suggested otherwise.

Dr DiNicolantonio said there was now a “strong argument” that the consumption of refined carbohydrates was the likely causative dietary factor behind the surge in obesity and diabetes in the US. While a low fat diet may lower ‘bad’ (LDL) cholesterol, there are two types of LDL cholesterol. Dr DiNicolantonio said switching to carbs may increase pattern B (small dense) LDL, which is more harmful to heart health than pattern A (large buoyant) LDL, as well as creating a “more unfavourable” overall lipid profile.

Furthermore, Dr DiNicolantonio said several other studies indicated that a low carb diet was better for weight loss and lipid profile than a low fat diet, while large observational studies had “not found any conclusive proof” that a low fat diet cuts cardiovascular disease risk.

Polyunsaturated fat intake increase problematic

In attempting to cut saturated fat intake, Dr DiNicolantonio said several dietary guidelines recommended increasing polyunsaturated fat intake.

However, Dr DiNicolantonio said recent analysis of published trial data showed that replacing saturated fats and trans fatty acids with omega 6 fatty acids, without a corresponding rise in omega 3 fatty acids, seemed to increase the risk of death from coronary heart and cardiovascular diseases.

“We need a public health campaign as strong as the one we had in the 70s and 80s demonising saturated fats, to say that we got it wrong,” Dr DiNicolantio said in a podcast that accompanied the editorial.

Dr DiNicolantonio said the best diet to boost and maintain heart health was one low in refined carbohydrates, sugars and processed foods.

Expert reaction

Heart health experts have responded to Dr DiNicolantonio’s editorial, welcoming the suggestion that dietary requirements for heart health are complex, but questioning a focus on sugar.

“This editorial is a welcome addition to the debate about what is known as the ‘lipid hypothesis’ of the dietary links to cardiovascular disease,” said Professor Brian Ratcliffe, Professor of Nutrition at Robert Gordon University in Aberdeen. “For the last three decades, accumulating evidence has not provided strong support for the dietary recommendations regarding reducing fat and saturated fat intake,” he said.

“DiNicolantonio does not even touch on the evidence which shows that low fat diets (admittedly lower than the current recommendations) have been associated with poor mood and even depression,” Professor Ratcliffe said. “Many who adhere to dietary dogma have chosen to ignore the uncomfortable facts that did not fit the hypothesis,” he said.

Professor Ratcliffe said the links between diet and cardiovascular diseases “are not easy to tease apart and much of the earlier work that supported the ‘lipid hypothesis’ used relatively crude methods”. However, Professor Ratcliffe criticised Dr DiNicolantonio making an association between increased intake of refined carbohydrates and the rise of obesity.

Whole diet approach to heart health, research finds

Meanwhile, a study published in The American Journal of Medicine has shown that a whole diet approach, which focuses on increased intake of fruits, vegetables, nuts and fish, has more evidence for reducing cardiovascular risk that strategies that focus exclusively on reduced dietary fat.

The study was co-authored by James E. Dalen, MD. MPH, Weil Foundation and University of Arizona College of Medicine and Stephen Devries, MD, FACC, Gaples Institute for Integrative Cardiology (Deerfield, Illinois) and Division of Cardiology, Northwestern University in Chicago.

The new study, undertaken by researchers at the University of Arizona College of Medicine and Northwestern University in Chicago, found that while strictly low fat diets had the ability to lower cholesterol, they were not as conclusive in reducing cardiac deaths. By analysing major diet and heart disease studies conducted over the last several decades, the researchers found that participants directed to adopt a whole diet approach instead of limiting fat intake had a greater reduction in cardiovascular death and non-fatal myocardial infarction.

“Nearly all clinical trials in the 1960s, 1970s and 1980s compared usual diets to those characterised by low total fat, low saturated fat, low dietary cholesterol and increased polyunsaturated fats,” said James E. Dalen from the University of Arizona College of Medicine. “These diets did reduce cholesterol levels. However, they did not reduce the incidence of myocardial infarction or coronary heart disease deaths,” he said.

“The potency of combining individual cardioprotective foods is substantial — and perhaps even stronger than many of the medications and procedures that have been the focus of modern cardiology,” said Stephen Devries, who was the co-author of the paper and is from the Gaples Institute for Integrative Cardiology and the Division of Cardiology at Northwestern University Chicago. “Results from trials emphasising dietary fat reduction were a disappointment, prompting subsequent studies incorporating a whole diet approach with a more nuances recommendation for fat intake,” he said.