A new systematic review of previously published studies has concluded that trans fats are associated with a greater risk of death and coronary heart disease, while saturated fats are not.
In fact, saturated fats were not associated with an increased risk of death, heart disease, stroke or type 2 diabetes, according to the review, which was published this week in the BMJ.
Saturated fats typically come from animal products such as meat, egg yolks, butter, milk and salmon, contributing about 10 percent of calories to the typical North American diet. In contrast, trans fats are produced industrially from plant oils and found in margarine, packaged baked goods and snack foods. They contribute about 2 percent of calories to the North American diet.
At present, dietary guidelines recommend limiting saturated fat consumption to less than 10 percent of daily caloric intake to reduce the risk of ischemic heart disease and stroke. Guidelines also recommend limiting trans fats to no more than 1 percent of total caloric intake.
In recent years, several studies have challenged the assertion that saturated fats are associated with cardiovascular risk. Last May, a cardiologist writing in The BMJ stated that the idea that saturated fat plays a role in heart disease is a myth, pointing out that since it was recommended that people remove it from their diets, cardiovascular risk has actually gone up. In another study, an international group of researchers reviewed 72 studies on heart risk and intake of fatty acids, reporting that there is no evidence to support guidelines calling for restricted consumption of saturated fats as a way to reduce heart disease risk.
Hoping to settle some of the conflicting science, the researchers behind this latest study pooled data from previously published observational studies, focusing their analysis on the associations of saturated fats and trans fats with all-cause mortality, coronary heart disease, cardiovascular disease deaths, ischemic stroke and type 2 diabetes.
Trans fats linked to 34 percent increase in all-cause mortality
The researchers could not find any clear associations between high intake of saturated fats and with health problems in the studies involving saturated fats, although they were unable to rule out the possibility that it could increase the risk of death from coronary heart disease.
In the studies involving trans fats, however, they found trans fat consumption was associated with a 34 percent increase in all-cause mortality, a 21 percent increase in the risk of coronary heart and a 28 percent increase in the risk of death from coronary heart disease.
Ironically, food manufacturers first turned to trans fats in the 1950s as part of a push to cut use of saturated fats in animal products, particularly lard and butter. In the future, “dietary guidelines must carefully consider the health effects of recommendations for alternative macronutrients to replace trans fats and saturated fats,” said lead author Dr. Russell de Souza, an assistant professor in the Department of Clinical Epidemiology and Biostatistics with the Michael G. DeGroote School of Medicine at McMaster University.
“If we tell people to eat less saturated or trans fats, we need to offer a better choice,” said Dr. de Souza. “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.”
In May, the Food and Drug Administration announced a series of new restrictions on the use of trans fats in food products sold in the U.S. Although many food manufacturers had already started to phase out their use of the unhealthy fats, they remain ubiquitous in packaged foods and snacks. FDA officials say the new limits, which go into effect over the next three years, could prevent an estimated 20,000 heart attacks and 7,000 deaths a year.