Current “heart-healthy” nutritional guidelines recommend replacing saturated fats with unsaturated fats, based on evidence that doing so reduces the risk of cardiovascular disease. Findings from a 2016 study suggest that these guidelines were established on incomplete evidence.

The study drew on previously unpublished data from the Minnesota Coronary Experiment (MCE). The MCE was a double-blind randomized controlled trial involving more than 9,000 participants conducted between 1968 and 1973. The trial investigated whether replacing saturated fat with vegetable oils rich in linoleic acid (a polyunsaturated fat) reduced coronary heart disease and death by lowering serum cholesterol. The authors of the current study re-analyzed unpublished findings and raw data from the MCE using the hypotheses posed by the original research team. They also conducted a systematic review and meta-analysis of other similar randomized controlled trials.

Their analyses showed that trials using vegetable oils rich in linoleic acids lowered cholesterol in the study participants but did not reduce risk of heart disease and death. In fact, participants with the lowest cholesterol levels in the MCE study were at higher risk, with every 30-point reduction in serum cholesterol equating to a 22 percent greater risk of death.

These findings suggest that data from randomized controlled trials do not support the theory that the cholesterol-lowering effects associated with replacing saturated fat with vegetable oils rich in linoleic acid translate to a reduced risk of heart disease or death. The authors of the study posited that failure to publish negative or inconclusive results can contribute to skewed research priorities and public health interventions.

• Link to full study.

• Listen to this podcast in which Dr. Rhonda Patrick discusses the controversy surrounding saturated fat intake and cardiovascular disease risk.