Replacing Saturated Fat with Unsaturated Fat and Carbohydrates Reduces Risk of Mortality

Looking to bring together the most current scientific evidence on the health effects of saturated fat, the World Health Organization recently conducted a comprehensive meta-analysis of 112 publications, involving over 3.5 million participants. The findings showed that replacing saturated fat–found mostly in meat, dairy, eggs, and some tropical oils–with polyunsaturated fat, monounsaturated fat from plant sources, or carbohydrates was associated with significant reductions in all-cause mortality and coronary heart disease incidence.

The researchers aimed to build on previous research by accounting for what other macronutrients the saturated fats were replaced with, allowing them to assess this topic in much more detail than other previous work. They also mitigated the limitations of relying on dietary assessment methods by also accounting for tissue and blood biomarkers to determine dietary intakes.

For all-cause mortality–the total risk of death during the studies–those eating the most saturated fat had an 8% higher risk of all-cause mortality than those eating the least. More specifically, further analyses showed that replacing 5% of total calories from saturated fat with polyunsaturated fat, monounsaturated fat from plants, and carbohydrates, reduced risk by 15%, 15% and 8% respectively. Replacing saturated fat with trans fat or monounsaturated fat from animal sources did not lead to any reductions in risk of all-cause mortality.

For coronary heart disease–the most common type of heart disease in the US–replacing 5% of calories from saturated fat with polyunsaturated fat, monounsaturated fat from plants or slow-digesting carbohydrates reduced risk by 11%, 17% and 6% respectively. But replacing 5% of calories from saturated fat with animal protein was associated with a 31% higher risk.

This detailed analysis provides further evidence that limiting saturated fat intake can benefit long-term health, while clearly showing that what we replace saturated fat with is also important. Aiming for healthy fats from plant sources and slow-digesting carbohydrates from foods like whole grains, legumes and starchy vegetables consistently leads to the greatest improvements in key health outcomes.

Reference

Reynolds, A., Hodson, L., de Souza, R., Tran Diep Pham, H., Vlietstra, L., Mann, J. (2023). Saturated Fat and Trans-Fat Intakes and Their Replacement with Other Macronutrients: A Systematic Review and Meta Analysis of Prospective Observational Studies. Geneva: World Health Organization; License: CC BY-NCSA 3.0 IGO.