A healthy approach to dietary fats: understanding the science and taking action to reduce consumer confusion

Abstract

Consumers are often confused about nutrition research findings and recommendations. As content experts, it is essential that nutrition scientists communicate effectively. A case-study of the history of dietary fat science and recommendations is presented, summarizing presentations from an Experimental Biology Symposium that addressed techniques for effective scientific communication and used the scientific discourse of public understanding of dietary fats and health as an example of challenges in scientific communication. Decades of dietary recommendations have focused on balancing calorie intake and energy expenditure and decreasing fat. Reducing saturated fat has been a cornerstone of dietary recommendations for cardiovascular disease (CVD) risk reduction. However, evidence from observational studies and randomized clinical trials demonstrates that replacing saturated fat with carbohydrates, specifically refined, has no benefit on CVD risk, while substituting polyunsaturated fats for either saturated fat or carbohydrate reduces risk. A significant body of research supports the unique health benefits of dietary patterns and foods that contain plant and marine sources of unsaturated fats. Yet, after decades of focus on low-fat diets, many consumers, food manufacturers, and restauranteurs remain confused about the role of dietary fats on disease risk and sources of healthy fats. Shifting dietary recommendations to focus on food-based dietary patterns would facilitate translation to the public and potentially remedy widespread misperceptions about what constitutes a healthful dietary pattern.

Fig. 1

Effects of isocaloric substitution of specific fatty acids for saturated fatty acids in the Nurses’ Health Study and Health Professional Follow-up Study on a.) total mortality, b.) cardiovascular disease mortality, c.) cancer mortality, d.) neurodegenerative disease mortality. Results were from the multi-variate model using the fixed-effects model. UFA indicates unsaturated fatty acid and error bard, 95% confidence intervals. Reproduced with permission from Wang, et al. 2016 [35]

Fig. 2

Dose–response analysis for the curvilinear association between dietary intake of linoleic acid and coronary heart disease deaths. P = 0.72 for nonlinearity relationship, indicating a linear relationship. %E indicates percent of energy. Reproduced with permission from Farvid et al. 2014 [41]

Fig. 3

Effects on CHD risk of consuming PUFA, carbohydrate, or MUFA in place of saturated fat. Predicted effects are based on changes in the total cholesterol (TC):HDL-C ratio in short-term trials (e.g., each 5% energy of PUFA replacing saturated fat lowers TC:HDL-C ratio by 0.16) coupled with observed associations between the TC:HDL-C ratio and CHD outcomes in middle-aged adults (each 1 unit lower TC:HDL-C is associated with 44% lower risk of CHD) [42]. Evidence for effects of dietary changes on actual CHD events comes from the present meta-analysis of eight randomized controlled trials for PUFA replacing saturated fat and from the Women’s Health Initiative trial for carbohydrate replacing saturated fat (n = 48,835, ~3% energy reduction in saturated fat over 8 years) [81]. Evidence for observed relationships of usual dietary habits with CHD events comes from a pooled analysis of 11 prospective cohort studies [34]. Reproduced with permission from Mozaffarian et al. 2010 [30]

Fig. 4

Meta-analyses of foods and coronary heart disease, stroke, and diabetes mellitus. BMI indicates body mass index; CHD, coronary heart disease; CI, confidence interval; CVD, cardiovascular disease; PC, prospective cohort; RCT, randomized clinical trial; and RR, relative risk. Adapted with permission from Circulation [74]