Role of Different Dietary Saturated Fatty Acids for Cardiometabolic Risk

David Iggman; Ulf Risérus

Clin Lipidology. 2011;6(2):209-223.

Different Types of Dietary SFA

Dietary SFA can be divided into animal and vegetable fat, according to origin. The tropical oils (i.e., palm oil, palm kernel oil and coconut oil) are high in SFA albeit of vegetable origin. However, there is also considerable heterogeneity in this category. Coconut oil is high in lauric acid (12:0), whereas palm oil mainly consists of palmitic acid (16:0) and oleic acid (18:1n-9). Overall, the most common dietary SFA are 16:0 and stearic acid (18:0), found in animal fat (~a half and a quarter of total SFA in beef, respectively), and also present in varying amounts in plants. Accordingly, these two SFA are also the major SFA in human plasma and tissues, which typically reflect dietary intake in western diets moderately high or high in total fat. Dairy fat is unique in that it contains a broad spectrum of short-chain (SC), medium-chain (MC) and long-chain (LC) SFA, besides monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA). Still, in most dairy products, the major fatty acid is 16:0. The MC SFA can be found in dairy, coconut oil and palm kernel oil.

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Executive Summary

Various metabolic effects of separate saturated fatty acids

Most dietary saturated fatty acids (SFA) are long chain 14:0–18:0.
Short-chain SFA may have a role in prevention of cancer and inflammation of the large intestine, medium-chain SFA may reduce adiposity, 12:0 may have antimicrobial properties, and 14:0 and 16:0 may have various regulatory functions in the cell via protein fatty acid acetylation.

Effects on cardiovascular risk factors

Long-chain SFA increase total cholesterol and LDL-C, except 18:0, which is neutral. Lauric acid (12:0) is the most potent SFA for raising cholesterol, but also reduces the total cholesterol:HDL-C ratio.
Some studies suggest an atherogenic and prothrombotic effect of 18:0, but not consistently. Whether 18:0 is preferable to 16:0 as a substitute for trans -fatty acids is not clear, but according to effects on blood lipids solely, this may be true.

Effects on cardiovascular disease

Overall, SFA consumption has not been clearly demonstrated to increase cardiovascular disease (CVD) in epidemiological studies using self-reported questionnaires, but the data may be weakened by reporting bias and residual confounding.
Exchanging SFA with polyunsaturated fatty acids decreases CVD risk and mortality.
Studies on individual SFA are limited but one large cohort study indicates an increased risk of coronary heart disease for 12:0, 14:0, 16:0 and 18:0, and biomarker studies suggest detrimental effects from circulating and tissue 16:0 content.

Effects on insulin resistance & diabetes

Long-chain SFA 16:0 and 14:0 seem detrimental to β-cell function in vitro and in animal experiments.
Biomarker studies have demonstrated associations between circulating 14:0, 16:0, and 18:0 and diabetes incidence, although this may only partly reflect dietary SFA intake.
Circulating 15:0 is inversely associated with diabetes incidence and may reflect dairy food intake, but also a 'healthy lifestyle', or other factors not captured due to residual confounding.

Dairy intake & cardiometabolic risk

High-fat dairy products raise LDL-C, and although controlled studies where dairy fat has been a major SFA source indicate increased CVD risk compared with polyunsaturated fatty acids, little epidemiological evidence exists for detrimental effects of dairy intake on disease end points, despite its SFA and trans -fatty acid content.
Milk fat biomarkers 15:0 and 17:0 have been inversely associated with insulin resistance and risk for myocardial infarction, but whether such relationships are explained by SFA-specific effects of dairy foods is unknown.
Long-term controlled intervention studies using high-fat dairy foods versus other types of fats are needed to confirm the epidemiological associations.
It will, however, be challenging to separate any potential health effect of dairy fat between the different individual SFA, as well as from other micronutrients and protein found in dairy products.