Higher intake of trans fat is associated with 20-30% increased risk of death and coronary heart disease, Canadian researchers have found.
However, saturated fats are not associated with an increased risk of death, heart disease, stroke, or type 2 diabetes, according to the study published in the British Medical Journal.
“Dietary guidelines for saturated and trans fatty acids must carefully consider the effect of replacement nutrients”
The study confirms previous suggestions that industrially produced trans fats – mainly produced industrially from plant oils – might increase the risk of coronary heart disease and calls for a careful review of dietary guidelines, said the researchers.
Guidelines currently recommend that saturated fats are limited to less than 10%, and trans fats to less than 1% of energy to reduce risk of heart disease and stroke.
The researchers analysed the results of observational studies assessing the association between saturated and/or trans fats and health outcomes in adults.
The team found no clear association between higher intake of saturated fats and all-cause mortality, CHD, cardiovascular disease, ischemic stroke or type 2 diabetes.
However, they said they could not rule out increased risk for death from CHD and they did not find evidence that diets higher in saturated fat reduced cardiovascular risk.
In contrast, consumption of industrial trans fats was associated with a 34% increase in all-cause mortality, a 28% increased risk of CHD mortality, and a 21% increase in the risk of CHD.
Inconsistencies in the studies included in the review meant the researchers could not confirm an association between trans fats and type 2 diabetes, and they found no clear association between trans fats and ischemic stroke.
The researchers also stressed that their results were based on observational studies, so no definitive conclusions can be drawn about cause and effect.
However, they said their analysis “confirms the findings of five previous systematic reviews of saturated and trans fats and CHD”.
They concluded that dietary guidelines for saturated and trans fatty acids “must carefully consider the effect of replacement nutrients”.