MIAMI • Saturated fats in butter, lard and red meat raise the risk of early death, but replacing these with fats like olive oil can offer substantial health benefits, a three-decade study has confirmed.
Results of the research involving more than 120,000 people were published this week in the Journal of the American Medical Association Internal Medicine.
"There has been widespread confusion in the biomedical community and the general public... about the health effects of specific types of fat in the diet," said lead author Dong Wang, a doctoral candidate at Harvard University's T.H. Chan School of Public Health.
"This study documents important benefits of unsaturated fats, especially when they replace saturated and trans fats."
One key finding was that people who ate more saturated and trans fats had higher mortality rates than those who ate the same amount of calories from carbohydrates.
The study also found that replacing saturated fats like butter, lard, and fat in red meat with unsaturated fats from plant-based foods like olive, canola and soyabean oils could offer "substantial health benefits and should continue to be a key message in dietary recommendations".
The findings were based on questionnaires answered by health professionals every two to four years about their diet, lifestyle and health for up to 32 years.
Trans fats, including partially hydrogenated oil products like margarine, had the most severe impact on health. The study found that every 2 per cent higher intake of trans fat was associated with a 16 per cent higher chance of dying early.
And every 5 per cent higher increase in consumption of saturated fats was linked to an 8 per cent greater risk of dying.
But eating higher amounts of unsaturated fats was linked with "between 11 per cent and 19 per cent lower overall mortality compared with the same number of calories from carbohydrates". These included polyunsaturated fats like omega-3 and omega-6 found in fish oils as well as soya and canola oils.
"People who replaced saturated fats with unsaturated fats - especially polyunsaturated fats - had significantly lower risk of death overall during the study period, as well as lower risk of death from cardiovascular disease, cancer, neurodegenerative disease and respiratory disease, compared with those who maintained high intakes of saturated fats," said the study.
While some experts noted that the study was observational and relied on surveys, which can introduce bias, the overall result is in line with many other large studies on diet and health.