Saturated fat consumption tends to increase circulation of low-density lipoprotein which in turn increases the risk of cardiovascular disease. Debate continues on how to replace the energy lost in reducing saturated fat – should we replace this energy with carbohydrate, protein or fat, and if fat, what type? Mozaffarian and colleagues aimed to address this question by systematically reviewing the effects on myocardial infarction and coronary death of partly replacing saturated fat intake by ω-6 polyunsaturated fatty acids (PUFA), including randomised controlled trials that continued for at least 12 months.