Recognition is sweet, even if it takes 40-odd years. For a long time many health experts recommended that you could eat as much polyunsaturated fat as you want.
New research now suggests that too much of even virtuous fats such as omega 3 from fatty fish and omega 6 from vegetable oil can cause problems.
Yet that is what a team of researchers in Sydney has been saying for 40 years. Sydney Diet Heart Study undertaken by University of NSW researchers from 1966 to 1973, took 458 men between the age of 30 and 59 years who had recently had a heart attack or experienced angina, and studied the health effects of replacing saturated fats with a higher intake of polyunsaturated fats.
The Sydney study found the group who had upped their omega-6 intake to 15 per cent of their daily calories had a higher risk of death from all causes, including cardiovascular disease, than the group who did not adjust their intake of saturated fats.
Given the popularity of polyunsaturated fats, contained in products such as margarine, the study was not widely recognised at the time.
But a new and more complete analysis of the data by American researchers at the US National Institute of Health has given it a renaissance, and could now challenge the American dietary recommendations.
In an editorial in the British Medical Journal that accompanied the re-publication of the data, British researcher Dr Philip Calder said the newly analysed research could question the “saturated fats bad, omega-6 good" dogma, 40 years after it was originally conducted.
The lead investigator on the Sydney Diet Heart Study, Dr
“We explained the adverse effect of [polyunsaturated fats] in the dietary trial. At the time we couldn’t explain it," Dr Boonseng said.
“We still should use polyunsaturated fats instead of excessive saturated fats but it’s the mix we need to be a bit more careful of now. America tends to promote higher omega-6 intake and it’s not a good way to do it."
The Sydney Diet Heart Study was Dr Boonseng’s first major project as a masters student, after he emigrated from Thailand at the age of 20.
He is humble about the new success of the study, saying it needed the research that has appeared in the past 40 years to support its findings.
“What the study shows is that polyunsaturated fats are not suitable in huge quantities," Ms Stanton said. “I don’t think you can extrapolate from this study that butter is suddenly good."
Australian dietary guidelines have always been more cautious than in the United States.
The guidelines recommend Australians replace foods high in saturated fats with foods that contain predominantly polyunsaturated and monounsaturated fats because these are less of a risk factor in coronary heart disease.
But the Australian Heart Foundation recommends consumption of 1 to 1½ tablespoons of healthier oils or fats a day.
By contrast, the American Heart Association tells consumers they should not worry about consuming too much omega-6 because it “may lower the risk of heart disease".
The Australian Financial Review