Even when researchers used better methods to measure what people ate or adjusted for more health factors like smoking and exercise, the link between saturated fat and heart disease still didn’t show up.

Different studies used different ways to measure what people ate — some asked about food habits over a year, others just asked what they ate yesterday — which might make it harder to see real links between diet and heart disease.

Multiple large-scale meta-analyses of prospective cohort studies demonstrate no statistically significant association between dietary saturated fat intake and incidence of coronary heart disease or cardiovascular disease.

This review looked at data from over 347,000 adults followed for an average of 14 years — so if saturated fat had even a moderate effect on heart disease, this study would have been able to find it.

Some big studies that looked at lots of people who ate less saturated fat didn’t find that they lived longer or had fewer heart attacks, which makes people question why we’ve been told to avoid foods like butter and cheese for so long.

Even when researchers accounted for how many total calories people ate or how much other fats they consumed, the link between saturated fat and heart disease still didn’t show up.