HEALTH warnings linking fat consumption to coronary heart disease "should not have been introduced", according to a study which turns decades of dietary advice on its head.

 

Loading article content

Consumers in the UK and US were first urged to cut their fat intake in 1977 amid fears that it raised blood cholesterol and led to coronary heart disease (CHD).

In particular, guidelines - reiterated in 1983 - advised millions of citizens to avoid foods high in saturated fats and ensure that calories from saturated fat accounted for no more than 10 per cent of their total energy intake. The recommendations added that calories from all types of fat should account for no more than 30 per cent of a person's diet - around 600 calories per day for a woman and 750 for a man.

However, a review of the clinical data underpinning the advice has concluded that it lacked any solid trial evidence to back it up and "should not have been introduced".

The six studies on which the advice was based were involved only male participants, with no significant difference in CHD deaths among the treatment groups - who underwent various dietary interventions - compared to the control groups, according to a study published in the journal Open Heart.

In addition, five of the six of the studies did not even test the theory that a maximum fat intake of 30 per cent, including10 per cent saturated, actually reduced the risk of developing CHD.

Instead, they examined the impact of swapping saturated fat for vegetable oil and reducing fat consumption to 20 per cent.

The researchers, from the University of the West of Scotland and Saint Luke's Mid America Heart Institute in Kansas City, said: "It seems incomprehensible that dietary advice was introduced for 220 million Americans and 56 million UK citizens, given the contrary results from a small number of unhealthy men...two recent publications have questioned the alleged relationship between saturated fat and CHD and called for dietary guidelines to be reconsidered.

"The present review concludes that dietary advice not merely needs review; it should not have been introduced."

Only one of the studies - a five-year randomised control trial in Sydney in the 1970s involving 458 men aged 30 to 59 - tested the benefits of reducing saturated fat intake to 10 per cent.

One group of men consumed a diet containing 10 per cent saturated fat and 15 per cent polyunsaturated fat, while the second group consumed 14 per cent saturated fat to nine per cent polyunsaturated fat.

Bizarrely, given the dietary advice which followed, mortality from all causes - but particularly coronary heart disease - was actually higher among the group consuming less saturated fat.

The authors of the Open Heart study, who include Zoe Harcombe of the University of the West of Scotland, write: "It is a widely held view that reductions in cholesterol are healthful per se.

"The original RCTs [randomised control trials] did not find any relationship between dietary fat intake and deaths from CHD or all-causes, despite significant reductions in cholesterol levels in the intervention and control groups.

"This undermines the role of serum cholesterol levels as an intermediary to the development of CHD."

In recent years, nutrition science has moved away from fat as the main culprit behind illness and obesity, with increasing numbers of studies highlighting the dangers posed by diets high in sugar and certain carbohydrates - which are, in essence, complex sugars.

In a linked editorial, Rahul Bahl, of the Royal Berkshire NHS Foundation Trust, warns that the limitations exposed by the Open Heart study does not mean the original advice itself is wrong since subsequent epidemiological studies have found a link between dietary fat and heart disease.

He added: "There is certainly a strong argument that an over-reliance in public health on saturated fat as the main dietary villain for cardiovascular disease has distracted from the risks posed by other nutrients, such as carbohydrates.

"Yet replacing one caricature with another does not feel like a solution."