A team of medical researchers has some good news for those who cook with butter but consider it a guilty pleasure: It might actually be good for you.

While the findings, published this week in the British Medical Journal, are not conclusive, they are compelling: researchers with the University of North Carolina’s School of Medicine (UNC) analyzed a 50-year-old unpublished study out of Minnesota and found reason to believe that cooking with corn oil instead of butter may actually be worse for heart health. It’s an idea that, if one day proven, would upend the conventional nutrition wisdom of the last several decades.

In the last year, a growing number of voices within the nutrition community have been making the case that low-processed fatty foods aren’t as bad for you as once thought. It’s an argument that has shown up in studies from around the world and also in articles challenging national policy decisions based on the idea that fat should be avoided.

In the case of butter versus vegetable oil, the UNC team analyzed unpublished nutritional data gathered between 1968 and 1973 in a controlled study that included more than 9,400 men and women in one nursing home and six state mental hospitals in Minnesota.

The subjects were broken into two groups. One was given a diet in which liquid corn oil was used in place of usual hospital cooking fats (including butter and hydrogenated oils) during meal preparation. The other group received meals cooked with common margarines and shortening. Roughly 57% of the 517 subjects that died during the course of the study underwent post-mortem examinations of their hearts, aortas, and brains. But no analysis of the data had been published until now.

After a review of available data, the UNC researchers determined that, overall, there was a 22% higher risk of death for participants on the vegetable oil diet. They argue that because an analysis of the study was never published, nutrition experts have over-emphasized the health benefits of substituting vegetable oils for butter.

To be sure, debate within the nutrition science community over the pros and cons of cooking with and consuming fats has been robust. Many studies have found cutting out butter and using more vegetable oil to be beneficial, but very few of those have included data from controlled trials—nutrition science can be difficult to carry out because of ethical considerations of testing diets on humans.

“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 Daisy Zamora, one of the UNC researchers.