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26 Oct 2018

PURE dietary advice

Research findings change the view on what is best for heart health

In a work called The physiology of taste, or, Meditations on transcendental gastronomy, French lawyer, politician and gastronome Anthelme Brillat-Savarin coined the phrase in 1826 that ‘you are what you eat.’

Some comprehensive and ground breaking international research has cast new meaning on this concept with some heart-felt views and advice. 

In the 21st Century the focus, and fascination, has been on the notion of your wellbeing is increasingly defined by what you eat.

Given its importance in keeping your body alive the relationship between diet and heart health has been a primary area of consideration. 

There is no argument that cardiovascular disease is a global epidemic with 80% of the burden of disease in low-income and middle-income countries.

Similarly, consensus is that diet is one of the most important modifiable risk factors for cardiovascular disease in addition to other non-communicable diseases.

 

Desperately seeking solutions

The search for the Holy Grail of creating the ultimate heart-health diet has produced a cornucopia of ideas, fads, recommendations, research and an array of conclusions about what best suits the human physiology. 

Along the way what has been considered as bona fide research conclusions have been debated, debunked or totally reconsidered. 

In one of the world’s most comprehensive studies—with the matter of fact title of Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study—popular beliefs have been turned upside down. 

The PURE in the title is an acronym referring to a Prospective Urban Rural Epidemiology.  The last word in the mix refers to the branch of medicine which deals with the incidence, distribution, and possible control of diseases and other factors relating to health.

By any standard the research was a massive undertaking providing a feast of information and findings. 

The dietary intake of 135,335 individuals, aged between 35-70, across 18 countries and over a time frame of January 1st 2003 and March 31st 2013 was assessed and analysed.  The focus was on the efficacy of existing knowledge as well as fresh information that might produce a change of perspective related to dietary contributions to better health.        

 

Excessive consumptions

For decades, guidelines have focused on reducing total fat and saturated fatty acid intake.  This was based on the presumption that replacing the latter with carbohydrate and unsaturated fats will lower LDL cholesterol (the so-called ‘bad’ cholesterol) and should therefore reduce cardiovascular disease events.

This perspective was predominantly based on selective emphasis on some observational and clinical data. 

Most of which has stemmed from European and North American populations where nutrition excess is more likely. 

Needless to say the applicability of these outcomes and conclusions to other populations has been open to speculation. 

In conducting the research the targeted outcomes were two fold. 

The primary were total mortality and major cardiovascular events (fatal cardiovascular disease, non-fatal myocardial infarction, stroke, and heart failure).

The secondary were all myocardial infarctions, stroke, cardiovascular disease mortality, and non-cardiovascular disease mortality.

The associations between consumption of carbohydrate, total fat, and each type of fat with cardiovascular disease and total mortality, were also assessed.   

 

 

Upending the status quo

Current published guidelines recommend a low-fat diet (<30% of energy) and limiting saturated fatty acids to less than 10% of energy intake by replacing them with unsaturated fatty acids.

These enduring recommendations on lowering saturated fatty acids, however, are largely based on one ecological study.

Observational studies done in European and North American countries, where the intake of saturated fatty acids (about 20% of total energy intake) and cardiovascular disease mortality, were both very high influenced the recommendations. 

Furthermore, dietary recommendations have traditionally been based on the assumption of a linear association between saturated fatty acid intake and LDL cholesterol, and then the association between LDL cholesterol and cardiovascular disease events.

This assumption does not consider the effect of saturated fatty acids on other lipoproteins.   

 

The Findings

The PURE study found that high carbohydrate intake (more than about 60% of energy) was associated with an adverse impact on total mortality and non-cardiovascular disease mortality.

By contrast, higher fat intake was associated with lower risk of total mortality, non-cardiovascular disease mortality, and stroke.

Furthermore, higher intakes of individual types of fat were associated with lower total mortality, noncardiovascular disease mortality, and stroke risk and were not associated with risk of major cardiovascular disease events, myocardial infarction, or cardiovascular disease mortality.

In short the findings do not support the current recommendation to limit total fat intake to less than 30% of energy and saturated fat intake to less than 10% of energy.

Moreover, Individuals with high carbohydrate intake might benefit from a reduction in carbohydrate intake and increase in the consumption of fats as this was associated with an adverse impact on total mortality.  Whereas, in contrast, fats (including saturated and unsaturated fatty acids) were associated with lower risk of total mortality and stroke.

Importantly there were no observed detrimental effect of fat intakes on cardiovascular disease events.

Should global dietary guidelines be reconsidered in light of the consistency of findings from PURE?  The researchers say ‘Yes’.  Whatever the case there is clear food for thought in the debate about the impact of what you eat has on your health and wellbeing. 

 

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