Public health

Is it time to relax the rules on dietary fat?

An international study has thrown into doubt long held dietary advice to reduce fat intake to prevent heart disease.

The PURE study, an observational study of over 135,000 people from 18 countries, found that a high carbohydrate intake (>60% of energy intake) was associated with a 28% risk of death.

High fat diets (about 35% of energy intake), including both saturated and unsaturated fats, were associated with a 23% risk of mortality.

The investigators said that advice to reduce fat was based on evidence from North America and Europe that may not apply to other countries. They called for global dietary guidelines to be reconsidered in the light of their findings.

Based on their research, average global diets consisted of over 60% energy from carbs and 24% from fats, but the best diets should have 50-55% carbs and around 35% fats.

Some, but not all local experts are convinced. Dr Alan Barclay, an accredited practising dietician in Sydney, questioned the data collection and the median follow-up of just 7.5 years.

“Food intake was only assessed at base-line using a Food Frequency Questionnaire (FFQ) that was validated using unstated methods and no results of the validation studies are presented in the paper. We therefore do not know how well the FFQ assessed people’s carbohydrate, fat and protein intakes in each country.”

“Based on our most recent national health survey, Australians consume on average just over 43% of energy from carbohydrate and 11.5% from saturated fat. On face value, this means that Australians should be consuming more carbohydrate and less saturated fat – consistent with our current dietary guidelines,” he said.

Professor Amanda Lee, from the Australian Prevention Partnership Centre, said while the paper makes an ‘important contribution to nutrition’ neither the sources of fats or carbohydrates were reported or controlled for in the study.

Professor Jennie Brand-Miller from the University of Sydney echoed those sentiments saying Australia was ‘ahead of the curve.’

“We recognised that carbohydrates were not created equal over three decades ago – some were harmful because they increased fluctuations in blood glucose (i.e. they had a high GI). Since then we have reduced our intake of added sugars and as well as high GI starches. Australians and the Australian food industry should be congratulated.”

So have we got in wrong in demonising fats?

Professor Grant Schofield, director of the Human Potential Centre at Auckland University of Technology, said there was a ‘sea change’ occurring about the diet-heart hypothesis.

“In the PURE study, there are low intakes of fat and saturated fat, and plainly we not only see no evidence of benefit, we see harm in increased all-cause mortality. PURE tells us, along with mounting other evidence, that it is finally time to move on from banishing dietary fat, including saturated fat.”

Professor Schofield recommended people eat less highly processed and refined foods, especially sugar and highly refined carbohydrates.

“The totality of the evidence says to ‘eat foods low in human interference’. If our food was clearly recently alive in nature, that’s a good start to a healthy diet.”

Mr Bill Shrapnel, director of Shrapnel Nutrition Consulting, said the NHMRC largely ignored this type of evidence during the development of the latest Australian Dietary Guidelines.

“The NHMRC chose not to review the Nutrient Reference Value for total carbohydrate intake, or the evidence for glycaemic load and chronic disease risk, or the evidence on the associations between dietary saturated fat, carbohydrate and coronary heart disease, all of which would have shed light on the issue.”

“Consequently, the latest Australian Dietary Guidelines were 10 years out-of-date when they were published,” he added.

Professor John Funder, from the Hudson Institute of Medical Research, described the investigation as a ‘good study’ that covered a range of countries with high, mid and low average income populations.

His advice about diet was balanced. “Go for dairy, olive oil and even the occasional wagyu beef burger, have lots of grains, fruit and vegetables, and lay off the sweet stuff – especially the empty calories in the 16 teaspoonfuls of trouble in sugar-sweetened soft drinks.”

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