Saturated fat found in butter, meat or cream is unlikely to kill you, but some margarines just might, new research suggests.
Although traditionally dieticians have advised people to cut down on animal fats, the biggest ever study has shown that it does not increase the risk of stroke, heart disease or diabetes.
However trans-fats raises the risk of death by 34 per cent.
And while most margarine makers have removed trans fat from their ingredients, you still need to double-check. The few that still contain trans fat have levels as high as 3 grams per serving.
"For years everyone has been advised to cut out fats," said study lead author Doctor Russell de Souza, an assistant professor in the Department of Clinical Epidemiology and Biostatistics, at McMaster University in Canada.
"Trans fats have no health benefits and pose a significant risk for heart disease, but the case for saturated fat is less clear.
"That said, we aren't advocating an increase of the allowance for saturated fats in dietary guidelines, as we don't see evidence that higher limits would be specifically beneficial to health."
Saturated fats come mainly from animal products, such as butter, cows' milk, meat, salmon and egg yolks, and some plant products such as chocolate and palm oils.
In contrast Trans unsaturated fats or trans fats - are mainly produced industrially from plant oils for use in margarine, snack foods and packaged baked goods.
Guidelines currently recommend that saturated fats are limited to less than 10 per cent, and trans fats to less than one per cent of energy, to reduce risk of heart disease and stroke.
Last year leading heart scientist Dr James DiNicolantonio of Ithica College, New York, called for health guidelines on saturated fats to be changed in an article in the British Medical Journal.
The "vilification" of saturated fats dates back to the 1950s when research suggested a link between high dietary saturated fat intake and deaths from heart disease.
But the study author drew his conclusions on data from six countries, choosing to ignore the data from a further 16, which did not fit with his hypothesis, and which subsequent analysis of all 22 countries' data.
Nevertheless the research stuck and since the 1970s most public health organisations have advised people to cut down on fat.
However the new research found no clear association between higher intake of saturated fats and death for any reason, coronary heart disease, cardiovascular disease, ischemic stroke or type 2 diabetes.
In contrast, consumption of industrial trans fats was associated with a 34 per cent increase in death, a 28 per cent increased risk of death from coronary heart disease, and a 21 per cent increase in the risk of cardiovascular disease.