Differential effects of saturated fatty acids on the risk of metabolic syndrome: a matched case-control and meta-analysis study

Background: We investigated the association between plasma saturated fatty acids (SFAs) and the risk of metabolic syndrome among ethnic Chinese adults in Taiwan who attended a health check-up center. Methods: A case-control study based on 1000 cases of metabolic syndrome and 1:1 matched control participants (mean age, 54.9 ± 10.7 y; 36% females) were recruited. Metabolic syndrome was defined according to the criteria of the International Diabetes Federation. Gas chromatography was used to measure the distribution of fatty acids in plasma (% of total fatty acids). Results: Even-chain SFAs, including 14:0, 16:0, and 18:0, were associated with metabolic syndrome; the adjusted odds ratio [OR] and 95% confidence interval [CI] per standard deviation [SD] difference was 3.32, [1.98–5.59]; however, very-long-chain SFAs, including 20:0, 21:0, 22:0, 23:0, and 24:0, were inversely associated with metabolic syndrome. The adjusted OR [95% CI] per SD difference was 0.67 [0.58–0.78]. The area under the receiver operative characteristic curve increased from 0.814 in the basic model to 0.815 (p = 0.54, compared with the basic model), 0.818 (p < 0.0001), and 0.820 (p < 0.0001) after adding odd-chain, even-chain, and very-long chain SFAs. A meta-analysis based on 12 studies showed that the summarized OR for type 2 diabetes mellitus was 1.16 [0.96–1.41] for the top versus bottom SFAs. Conclusions: Different carbon numbers of SFAs have been shown to have differential effects on the status of metabolic syndrome, implying that SFAs are not homogenous for the effects.