No matter who you ask, they’ll tell you the same thing: butter isn’t good for you, just use vegetable oil. But while butter may not be the healthiest of foods, new research has found that replacing it with vegetable oils does not decrease risk of heart disease.

Photo by Steve Karg.

The main culprit is linoleic acid – a polyunsaturated omega-6 fatty acid. The research, which was studied in the British Medical Journal, suggests that using vegetable oils high in linoleic acid might be worse than using butter when it comes to preventing heart disease. Basically, their study found not that butter is better for you, but that vegetable oils are worse for you: their benefits were overestimated and their risks were underestimated.

“Altogether, this research leads us to conclude that incomplete publication of important data has contributed to the overestimation of benefits — and the underestimation of potential risks — of replacing saturated fat with vegetable oils rich in linoleic acid,” said co-first author Daisy Zamora, PhD, a researcher in the Department of Psychiatry at the UNC School of Medicine.

The findings were confirmed for corn oil, as well as safflower oil, soybean oil, sunflower oil, and cottonseed oil. As far as I could find, olive oil seems to not be so bad for your health.

The idea that butter is bad for you and should be replaced with vegetable oils emerged in the 1960s, when studies began to show that this dietary switch lowered blood cholesterol levels. Since then, several studies have shown that vegetable oils are better for you than butter, but several randomized controlled trials were unable to demonstrate that linoleic acid-based dietary interventions reduce the risk of heart attacks or deaths.

The biggest trove of data available comes from the Minnesota Coronary Experiment (MCE), which was conducted by Minnesota researchers between 1968 and 1973. It enrolled 9,423 patients in six state mental hospitals and one state-run nursing home. Its results did not appear in a medical journal until 1989. The investigators reported then that a switch to corn oil from butter and other saturated fats did lower cholesterol levels but made no difference in terms of heart attacks, deaths due to heart attacks, or overall deaths. But not all the data from that study was published, and some doubts were cast on the initial conclusions.

“Looking closely, we realized that some of the important analyses that the MCE investigators had planned to do were missing from the paper,” Zamora said.

They recovered much of the data of the original study and added new data to their existing datasets from the Sydney study and the other three published randomized clinical trials of linoleic acid-based dietary interventions. All of the information put together seemed to point into one direction: switching the butter out of your diet and replacing it with vegetable oils doesn’t make much of a difference when it comes to heart diseases.