In a setback to those who have switched to low-saturated fat diets for better heart health, a leading US cardiovascular research scientist has claimed diets low in saturated fat or based on Omega 6 fats do not curb heart disease risk or help you live longer.

"Current dietary advice to replace saturated fats with carbohydrates or omega 6-rich polyunsaturated fats is based on flawed and incomplete data from the 1950s," declared James DiNicolantonio in the medical journal Open Heart.

The best diet to boost and maintain heart health is one low in refined carbohydrates, sugars and processed foods, he recommended.

Anyone who has had a heart attack should not be thinking of replacing saturated fats with refined carbs or omega 6 fatty acids -- particularly those found in processed vegetable oils containing large amounts of corn or safflower oil, he added.

"Dietary guidelines should be urgently reviewed and the vilification of saturated fats stopped to save lives," he insisted.

DiNicolantonio said the idea that fat causes heart disease was based on a flawed 1950s study which used data from six countries but excluded data from another 16.

This study "seemingly led us down the wrong 'dietary road' for decades to follow", he said.

There is now a strong argument in favour of the consumption of refined carbohydrates as the causative dietary factor behind the surge in obesity and diabetes in the US.

While a low fat diet may lower 'bad' (LDL) cholesterol, there are two types of LDL cholesterol.

"Switching to carbs may increase pattern B (small dense) LDL which is more harmful to heart health than pattern A (large buoyant) LDL, as well as creating a more unfavourable overall lipid profile," DiNicolantonio noted.

In the race to cut saturated fat intake, several dietary guidelines recommend upping polyunsaturated fat intake.

However, a recent data shows that replacing saturated fats and trans fatty acids with omega 6 fatty acids, without a corresponding rise in omega 3 fatty acids, seems to increase the risk of death from coronary heart and cardiovascular diseases.

"We need a public health campaign as strong as the one we had in the 70s and 80s demonising saturated fats, to say that we got it wrong," urged DiNicolantonio.

"Eating a Mediterranean-style diet rich in fruit, veg, pulses and fish would help lower cholesterol and reduce the risk of coronary heart disease," he suggested.