I’ve been confused by the seemingly conflicting studies and guidelines on saturated fat that have been released the past few years. This study from Harvard School of Public Health makes a pretty strong case that it really does make sense to replace saturated fat with unsaturated fat.

When it comes to saturated fat, what you replace it with matters. People who replaced saturated fat in their diets with unsaturated fats—especially polyunsaturated fats—had a far lower risk of death from any cause, as well as death due to cardiovascular disease, cancer, neurodegenerative disease, and respiratory disease. Those who replaced saturated fat with carbohydrates only slightly lowered mortality risk. This is most likely because carbohydrates in typical American diets are high in refined starch and sugar, which have a similar influence on mortality risk as saturated fats…

The recent widespread confusion about the health effects of specific types of dietary fat is in part caused by a misleading 2014 Annals of Internal Medicine paper, which concluded there is no evidence supporting the longstanding recommendation to limit saturated fat consumption and replace it with unsaturated fats. The authors of this paper employed a meta-analysis (a statistical analysis that summarizes data from many different studies), and therefore could not look at specific macronutrient comparisons with saturated fat. In addition, this paper also had errors in data extraction, omitted important studies, and only examined coronary heart disease.

In addition, a recently published BMJ paper based on 1960’s data from the Minnesota Coronary Experiment suggested that replacing saturated fat with vegetable oils rich in linoleic acid was not protective against death from coronary heart disease or all causes, which appeared to challenge current guidelines and added further confusion. However, this study was of very short duration, extremely low in follow-up rate, and the intervention likely reduced intake of important omega-3 polyunsaturated fatty acids. The extreme intervention diet was also never consumed by any appreciable number of Americans and likely confounded by intake of trans fat.

Finally, a new systematic review and meta-analysis looking at the association of butter consumption (a concentrated source of saturated fat) with chronic disease and all-cause mortality resulted in headlines touting “butter is back,” even though the findings were predominantly neutral, and the authors pointed out that unsaturated fats were found to be a better choice than butter.