A systematic review and meta-analysis of observational studies found trans fats were associated with an increased risk for all cause mortality, total coronary heart disease and coronary heart disease mortality.
However, the researchers from Canada also found that saturated fats were not associated with all cause mortality, cardiovascular disease, coronary hear disease, coronary heart disease mortality, ischemic stroke or type 2 diabetes. Results were published online in the British Medical Journal on Aug. 12.
“For years everyone has been advised to cut out fats,” lead researcher Russell de Souza of McMaster University in Ontario said in a news release. “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.”
The researchers noted that dietary guidelines suggest people limit saturated fats to less than 10 percent and trans fats to less than 1 percent of their energy in order to reduce the risk of ischemic heart disease and stroke.
They searched for observational studies that were published through May 1, 2015, in numerous databases, including Medline, Embase, Cochrane Central Registry of Controlled Trials, Evidence Based Medicine Reviews and CINAHL.
In all, there were 41 articles that reported an association between saturated fats and health outcomes in prospective cohort studies. Patients were enrolled in the U.S., the U.K., Japan, Sweden, Israel, Finland, Denmark, Canada, China, Greece and Australia.
They noted that consuming trans unsaturated fatty acids was associated with a 34 percent increase in all cause mortality, a 28 percent increased risk of coronary heart disease mortality and a 21 percent increase in the risk of coronary heart disease. Further, industrial trans fats were associated with a 30 percent increase in the risk of coronary heart disease events and an 18 percent increase in the risk of coronary heart disease mortality.
The researchers noted that large, longitudinal cohort studies with long follow-up periods are needed to observe clinical events and deaths and help identify dietary advice.
“If we tell people to eat less saturated or trans fats, we need to offer a better choice,” de Souza said. “Unfortunately, in our review we were not able to find as much evidence as we would have liked for a best replacement choice, but ours and other studies suggest replacing foods high in these fats, such as high-fat or processed meats and donuts, with vegetable oils, nuts, and whole grains.”