Dietary Intake of Linoleic Acid, Its Concentrations, and the Risk of Type 2 Diabetes: A Systematic Review and Dose-Response Meta-analysis of Prospective Cohort Studies

BACKGROUND Earlier evidence on the association between dietary polyunsaturated fatty acids and risk of diabetes has been conflicting. PURPOSE To quantitatively summarize previous studies on the association between dietary LA intake, its biomarkers, and the risk of type 2 diabetes mellitus (T2DM) in the general population. DATA SOURCES Our data sources included PubMed/MEDLINE, Scopus, and ISI Web of Science until 24 October 2020; reference lists of all related articles; and key journals. STUDY SELECTION We included prospective cohort studies that examined the associations of linoleic acid (LA) with the risk of T2DM in adults. DATA SYNTHESIS The inverse variance method was applied to calculate summary relative risk (RR) of LA intake and its biomarkers, and dose-response associations were modeled using restricted cubic splines. Twenty-three publications, covering a total of 31 prospective cohorts, were included; these studies included 297,685 participants (22,639 incident diabetes cases) with dietary intake assessment and 84,171 participants (18,458 incident diabetes cases) with biomarker measurements. High intake of LA was associated with a 6% lower risk of T2DM (summary relative risk [RR] 0.94, 95% CI 0.90, 0.99; I-2 = 48.5%). In the dose-response analysis, each 5% increment in energy from LA intake was associated with a 10% lower risk of T2DM. There was also evidence of a linear association between LA intake and diabetes, with the lowest risk at highest intakes. The summary RR for diabetes per SD increment in LA concentrations in adipose tissue/blood compartments was 0.85 (95% CI 0.80, 0.90; I-2 = 66.2%). The certainty of the evidence was assessed as moderate. LIMITATIONS A limitation of our work was the observational design of studies included in the analyses. CONCLUSIONS We found that a high intake of dietary LA and elevated concentrations of LA in the body were both significantly associated with a lower risk of T2DM. These findings support dietary recommendations to consume dietary LA.