Claim: ‘Saturated fat is not bad for your health’

The Daily Telegraph reported on 6 March 2014 that a US heart expert, James DiNicolantonio, had claimed that “saturated fat is not bad for health”. In an article published in BMJ Open Heart, DiNicolantonio argues that diets low in saturated fat do not lower cholesterol, prevent heart disease or strokes, or indeed help people live longer. These claims effectively placed him in opposition to decades of established medical and public health advice which has encouraged people in nations such as the USA and the UK to carefully monitor their intake of foods high in saturated fat.

Upon further investigation, it became clear that DiNicolantonio was not alone in the scientific community in holding such views. Many of these commentators and scientists attribute higher incidences of obesity, diabetes, coronary and cardiovascular disease, to the increased consumption of carbohydrates and sugars.

True or False?

With no reference to proportion or moderation, the claim that saturated fat is “not bad for your health” is considered to be largely false.

Largely FalseAnalysis

James DiNicolantonio told The Henry Mayhew Foundation that “there is no proof that eating saturated fat from [natural, not processed] foods is harmful”, and went further by arguing that no scientific proof existed to substantiate ‘low-fat diets’. His conclusion criticised a study by Keys et al (1957) which he says began the “vilification” of saturated fat and “led us down the wrong ‘dietary road’ for decades to follow” (the study openly excluded data from countries which produced results that did not fit the initial hypothesis).

Professor Bruce Griffin of the University of Surrey told us that despite being heavily criticised for the selective conclusion, their observations must have held some truth as they later formed the basis of equations predicting the impact of fatty acids on cholesterol levels.

The Daily Telegraph article did not make any reference to proportion, or moderation of saturated fat intake, but did correctly identify foods such as butter, cheese, fatty meat, biscuits, cakes and sausages as being high in saturated fat. However, DiNicolantonio maintained that his point about saturated fat not being harmful was only in reference to saturated fat naturally found in “real food”, and not processed foods such as savoury snacks and refined meat. In support of his assertions, DiNicolantonio highlighted a meta-analysis of randomized trials in humans (BMJ-2013, Chris Ramsden) which showed that replacing saturated fat with polyunsaturated fat potentially increases the risk of death due to coronary heart disease (CHD) and cardiovascular disease (CVD).

DiNicolantonio attributed the long-standing link between saturated fat and increased blood cholesterol levels to trials which used saturated fat as a single macronutrient, whereas in the average diet, a person does not normally consume a single type of saturated fat. Furthermore, he questioned the link between falling cardiovascular disease rates (in the UK) and public health advice which warns people to limit their saturated fat intake (around 25% of a person’s cholesterol comes from animal products – see LDL cholesterol). This, he argued, may show correlation, but not causation, and reflected on how the use of statins, aspirin and other medical interventions may have contributed to these figures.

Professor Bruce Griffin cited major clinical trials performed in the 1950’s by LW Kinsell and EH Ahrens as providing the foundation for the widely held belief that saturated fat increases blood cholesterol levels. In these trials, all elements of the subjects’ diet were kept constant, other than the intake of saturated fat (SFA) and unsaturated fat provided in milkshakes. The researchers found that when the milkshake contained SFA (from butter, lard and coconut oil) blood cholesterol was increased. When it contained unsaturated fat from corn and safflower oil, cholesterol levels decreased.

Importantly, in light of DiNicolantonio’s assertions, the findings were produced with real foods, and not industrialised trans-fats, and their results were replicated by other groups. He emphasised that a consensus statement from a panel of experts who were assembled to address these issues in 2011, concluded that the risk of CHD is decreased when dietary saturated fats were replaced with polyunsaturated fatty acids (PUFAs).

Professor Tom Sanders went on to reiterate that DiNicolantonio’s article “misinterpreted and misrepresented the relationship between saturated fat and CVD” and he argued that sugar intake did not in fact affect LDL cholesterol (the ‘bad cholesterol’) or blood pressure. Sanders cited the falling rates of CVD as evidence that a clear link existed between intake of saturated fat and a person’s levels of LDL cholesterol and blood pressure. The prevailing scientific view remains to be that a high saturated fat intake increases the risk of CHD and CVD.

A ‘Mediterranean diet‘ (typically found in Greece, Spain and Southern Italy), which is low in saturated fat (7-8% of dietary energy comes from saturated fat, with total fat ranging from 25% to 35% of energy intake), has consistently been held to be an example of the model diet. Incidences of coronary heart disease and certain cancers in the region are among the lowest in the world and life expectancies are among the longest. Thus, it would seem that promotion of moderation with regard to intake of saturated fat, (an approach adopted by Public Health England [PHE]), was not considered by The Daily Telegraph, which instead adopted an alarmist tone that meant current guidelines may be “putting the public at risk”.

The Daily Telegraph’s claim that “butter is not bad for the heart” does not accurately reflect the BMJ article’s contentions. DiNicolantonio’s argument attempts to prove there is no evidence a low-fat diet decreases our risk of developing degenerative heart diseases and speculates over the potential harms of replacing these saturated fats with carbohydrates or polyunsaturated fats. There is no doubt that misinterpreting scientific commentary can lead to irresponsible headlines such as the Belfast Telegraph’s: ‘Enjoy your Ulster fry, but ditch sugar‘.

PHE told The Henry Mayhew Foundation that “the totality of the evidence suggests that high saturated fat intake is associated with raising…blood cholesterol levels which, over time, could lead to an increased risk of developing heart disease”. They also added that the Scientific Advisory Committee on Nutrition (SACN) was currently reviewing the evidence on dietary carbohydrates and health and that a report would be made public in summer 2014.

Commentary

The link between saturated fat and heart disease continues to be questioned, however, headlines that imply we should not worry about our total saturated fat intake, and instead worry about carbohydrates and sugar are both irresponsible and misleading. Professor Tom Sanders concluded his observations by advising that “a diet is not like drugs, it is something [you] do for a lifetime and so it is virtually impossible to do randomized controlled trials demonstrating benefit in terms of mortality”.

 

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