Saturated Confusion

For more than 30 years, health officials have advocated dietary changes to overcome a spectrum of nutrition-related problems observed in children, adolescents, and adults. In 1979, while Vice Admiral Julius Richmond was surgeon general, Healthy People, The Surgeon General’s Report on Health Promotion and Disease Prevention noted dietary fat as a potential risk factor contributing to cardiovascular disease (U.S. Dept. of Health, Education and Welfare 1979). Each of the subsequent Dietary Guidelines for Americans—1980 through 2010—recommended diets low in fat and cholesterol.

During public deliberations of the 2015 Dietary Guidelines Advisory Committee, members commented that the evidence no longer supports low-fat dietary patterns. The final recommendations noted that managing total dietary fat and dietary cholesterol are no longer primary health issues; however, elevated dietary saturated fat remains a health concern. The American Heart Assoc. recommends limiting saturated fats to 5%–6% of total energy intake (approximately 13 g per day) due to its strong association with cardiovascular disease (CVD) risk.

In particular, dietary saturated fat seems to increase blood levels of low-density lipoprotein (LDL) cholesterol, a CVD risk factor. The Dietary Guidelines for Americans recommends an upper limit of 10% of total calories from saturated fat for the same reason. According to the most recent U.S. Dept. of Agriculture (USDA) data, the typical American consumes about 11% of their total energy in the form of saturated fat (USDA 2015).

A recent meta-analysis of 72 studies addressed the association of dietary saturated fats and the risk of CVD (Chowdhury et al. 2014). This study indicated no association between total dietary saturated fat and the risk of CVD based on classic biomarkers, despite several numerical corrections. This conclusion mirrored the findings of an earlier meta-analysis of 21 studies (Siri-Tarino et al. 2010). While there were common studies in these analyses and each of these studies may be questioned for quality, homogeneity, questionnaire validity, missing data, and confounding factors, several subsequent systematic reviews may further challenge and complicate our understanding of the dietary fatty acid and CVD association.

Schwingshackl and Hoffmann (2016) evaluated dietary patterns, particularly dietary fats, relative to CVD and all-cause mortality. Pooling data from 12 studies from 1965 through 2013 that included 7,150 subjects with pre-existing coronary heart disease did not indicate any clinical benefits associated with fat-modified diets and the risk of CVD. Interestingly, the analysis of this data set did not support the current mantra that the introduction of polyunsaturated fatty acids to replace saturated fatty acids would reduce the risk of developing CVD, at least within a cardiac-compromised population.

Another recent examination regarding butter consumption and CVD risk contributed additional confusion to dietary saturated fat and risk of CVD (Pimpin et al. 2016). As a point of reference, the annual per capita intake of butter in 2013 was approximately 5.5 lb, according to USDA Economic Research Service data. This is equivalent to about 2.8 lb of saturated fat (about 1.5 tsp or 4.7 g/day) ~22% of which is palmitic acid (C16) and ~10% of which is stearic acid (C18), with the balance primarily with carbon chain lengths of 14 or less, according to the USDA National Nutrient Database.

Nine publications that included 15 country-specific cohorts and represented more than 600,000 subjects and 6.5 million person-years were evaluated for potential association of butter consumption and CVD, diabetes, and all-cause mortality (Pimpin et al. 2016). The typical daily consumption of 14 g/day (~1 tablespoon) of butter was not significantly associated with coronary heart disease (p=0.737) and was inversely associated with diabetes (p=0.21). As noted in the 2015 Dietary Guidelines for Americans, foods vary in their fatty acid profiles, and food matrices contribute to distinct lipid and metabolic effects.

Assessment of dietary patterns based on the NHANES data indicates the American public continues to improve on food choices and nutrient intake (Rehm et al. 2016). Of particular interest is that there appears to be a slight decline in saturated fat consumption between 1999–2000 and 2011–2012. Concomitant dietary changes included increased consumption of whole grains, fish, nuts, and legumes. These observations are important as dietary policies strive to advance recommendations for healthful living patterns and practices such that the burdens of CVD and other noncommunicable diseases can be reduced (Mozaffarian 2016).

For another discussion of fat, diet, and health, see the article A Big Fat Dispute.

Roger Clemens, DrPH, CFS, Contributing Editor
Adjunct Professor, Univ. of Southern California School of Pharmacy, Los Angeles, Calif.
[email protected]