Impact of Replacement of Individual Dietary SFAs on Circulating Lipids and Other Biomarkers of Cardiometabolic Health: A Systematic Review and Meta-Analysis of Randomized Controlled Trials in Humans.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 34849532 · doi:10.1093/advances/nmab143
What was done
Authors conducted a systematic review and random-effects meta-analysis of 44 randomized controlled trials (mean participant age 39.9 ± 15.2 years) identified via PubMed, Embase, Scopus, and Cochrane CENTRAL through February 2021. The review evaluated the effects of isoenergetic dietary replacement of individual saturated fatty acids (SFAs) with other SFAs or unsaturated fatty acids (UFAs) for at least 14 days on fasting cardiometabolic risk markers, including lipids, glycemic control, inflammatory markers, and metabolic hormones. Study quality was evaluated using the Cochrane Risk of Bias 2.0 tool.
What was found
Replacing dietary palmitic acid (16:0) with UFAs significantly lowered LDL cholesterol (-0.36 mmol/L; 95% CI: -0.50, -0.21 mmol/L; I2 = 96.0%, n = 18 RCTs), with a similar impact on total cholesterol and apoB concentrations. Replacing palmitic acid with oleic acid (18:1n-9) also reduced LDL cholesterol (-0.16 mmol/L; 95% CI: -0.28, -0.03 mmol/L; I2 = 89.6%, n = 9 RCTs). No effects were observed on HDL cholesterol, triacylglycerol, glucose, insulin, or C-reactive protein. Replacing dietary stearic acid (18:0) with UFAs showed no evidence of benefit on cardiometabolic disease risk markers (n = 4 RCTs).
Why it matters
The findings confirm that replacing palmitic acid with unsaturated fats improves atherogenic lipid profiles in line with public health guidelines, while demonstrating that individual saturated fatty acids exert distinct cardiometabolic effects.
Limits
Statistical heterogeneity was extremely high (I2 > 89% for primary lipid outcomes). The total number of participants across trials was not reported in the abstract. Data for SFAs other than palmitic acid were limited to few trials, and outcomes were restricted to short-term surrogate biomarkers rather than clinical cardiovascular events.
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