What makes up a healthful diet, for the average person? Books with somewhat inflammatory titles like Sugar Kills, published in 2017, call attention to the history of American dietary recommendations that promoted processed carbohydrates rather than healthy fats in the diet. Along with research into the history of American dietary guidelines, inquiries into labeling requirements for snack foods, and increasing interest into healthy eating and wellness in the general population, research into the benefits of various dietary patterns is thriving. Of particular interest is dietary fat intake. Dietary fat intake is experiencing resurgence in acceptance in as processed carbohydrates and sugar decline in popularity. The 2015-2020 Dietary Guidelines for Americans have, happily, been updated to include recommendations that Americans “limit calories from added sugars and saturated fats,” and encourage Americans to eat “a variety of nutrient-dense foods,” including fatty fish, nuts and seeds, and other foods like avocado that contain an abundance of monounsaturated and polyunsaturated fatty acids, also known as MUFA and PUFA.
Longitudinal cohort studies support the government’s recommendations to eat a nutrient-dense and relatively unprocessed diet. A 2016 analysis published in the academic journal JAMA Internal Medicine used data from the Nurses’ Health Study and Health Professionals Follow-up Study to investigate the health effects of intake of total and specific dietary fat. The study focused on trans fat, saturated fat, and the unsaturated fats MUFA and PUFA, including omega-3 and omega-6 fatty acids. Researchers analyzed food frequency and mortality data from over 125,000 adults over approximately 30 years with the objective of finding an association between consuming dietary fats and total and cause-specific mortality.
The study found that dietary total fat was inversely associated with total mortality, compared to total carbohydrate consumption and after adjustment for known and potential confounding variables: consuming carbohydrates was associated with greater risk of mortality than was consuming fat, but the association depended on what type of fat was consumed since not all fats are created equal. Consumption of saturated and trans fats were found to be positively associated with total mortality, while consuming more MUFA and PUFA was association with lower mortality. Indeed, “replacing 5% of energy from saturated fats with equivalent energy from PUFA and MUFA was associated with estimated reductions in total mortality of 27% and 13%, respectively.” While saturated fats are associated with total mortality, research does not show that saturated fat has a specific impact on cardiovascular disease.
The types and quality of fats affect health outcomes and risk of mortality at a population level. Minimizing trans fat in the diet is recommended by both current American dietary guidelines and current research. Substituting MUFA and PUFA for trans and saturated fats can have a positive effect on clinical outcomes and mortality.