AHA experts reiterate importance of limiting saturated fatsSome studies say the saturated fats found in butter, fatty meats and other animal products have no effect on whether you get heart disease. Other studies say the science undeniably proves a connection between the two.

So, which should you believe? Nutrition experts with the American Heart Association say the answer is the same as it has been for decades – saturated fats can be harmful and should be limited in an overall healthy diet.

“It’s clear without a doubt that saturated fats raise LDL cholesterol, which we know contributes to heart disease. There’s just no doubt about that,” said Penny Kris-Etherton, Ph.D., R.D., a nutrition professor at Penn State University who serves as a volunteer on the AHA’s Nutrition Committee.

The issue of dueling nutrition studies arose again recently when an author cited studies in an essay claiming saturated fats may not be so bad for you.

The confusion stems from the type of study being conducted, Kris-Etherton said. The essay cited observational research studies, which can be very useful in some cases but can be unreliable or wrong when it comes to compiling dietary information, Kris Etherton said.

People in these studies self-report what they eat, often responding to questionnaires that are limited or flawed. Or, there may be a considerable lag between when they disclose the foods they eat and when they have a heart problem. It’s a problem that nutrition scientists often struggle with – in fact, Kris-Etherton discussed this data-gathering problem during a presentation at a scientific conference May 5.

Conversely, more reliable clinical trials in which scientists accurately measured what people were eating have found an undeniable link between saturated fats and heart disease. Those studies are the gold standard because the data can be independently verified.

“Randomized clinical trials addressing this question are history and demonstrate the benefit of saturated fat restriction,” said Robert Eckel, M.D., a former AHA president and professor of medicine at the University of Colorado Anschutz Medical Campus in Aurora.

Eckel served as the co-chair for an expert committee that developed the healthy living guidelines released by the AHA and American College of Cardiology in November 2013 – which was a major scientific undertaking that also recommended limiting saturated fats as part of an overall healthy diet to lower blood pressure and “bad” cholesterol (LDL).

The guidelines were developed by some of the nation’s top scientists, who for five years studied existing research and then issued recommendations that help healthcare professionals treat patients. The scientists concluded that saturated fat should be no more than 5 percent to 6 percent of daily calories.

The AHA recommends this limited intake as part of a healthy eating plan that includes plenty of fruits, vegetables, non-fat dairy products, lean meat and whole grains.

Understanding the kind of scientific research that goes into such dietary guidance is important, Eckel said.

“People should remember to turn to reliable sources that use evidence-based scientific findings for their recommendations,” he said.

Additional evidence of the link between heart disease and saturated fats came out in a 2012 analysis that reviewed several existing studies. The author of the analysis published in the independent not-for-profit Cochrane Reviews concluded that people should continue to limit saturated fats for health reasons.

The AHA has been issuing dietary recommendations for decades, and in 1961 for the first time recommended vegetable oils in place of saturated fats. The U.S. government issued guidelines discouraging saturated fats in 1980.

Science-based guidelines and recommendations have been an important part of the AHA’s efforts to fight heart disease and stroke. And while heart disease and stroke remain major threats, there has been significant progress over the years.

Death rates from heart disease and stroke have fallen steadily in the past 10 years, with heart disease dropping 39 percent and stroke dropping 36 percent.