According to study results published in PLoS Medicine, higher concentrations of fatty acid biomarkers, which partly reflect dairy fat intake, were associated with lower incidence of type 2 diabetes (T2D).
The investigators of this prospective study sought to examine the associations between the incidence of T2D and potential biomarkers of dairy fat intake, specifically circulating or adipose proportions of pentadecanoic acid (15-carbon saturated fatty acid, 15:0), heptadecanoic acid (17:0), and trans-palmitoleic acid (trans-16:1n7).
Researchers performed individual-level analysis on 16 prospective cohorts from 12 countries (7 from the United States, 7 from Europe, 1 from Australia, and 1 from Taiwan) that included a total of 63,682 participants without known diabetes at baseline. In each cohort, fatty acid concentrations were measured using gas chromatography in ≥1 lipid compartment. Over an average 9-year follow-up period, 15,180 cases of incident T2D were identified in participants who met 1 or more established clinical criteria. Follow-up periods were calculated from time of baseline fatty acid measurement to date of T2D development, any cause of death, censorship at end of follow-up, or loss to follow-up. Inverse-variance weighted meta-analysis was used to evaluate pooled relative risks, which were assumed to represent hazard ratios (HRs).
Prespecified variables including age, gender, body mass index, and race/ethnicity were evaluated using meta-analysis. Meta-regression analysis was also conducted to assess potential heterogeneity caused by cohort-specific characteristics, including geographic regions and lipid compartments used for fatty acid assays.
After adjusting for potential confounders, including adiposity and lipogenesis measures, higher levels of the 3 fatty acid biomarkers (15:0, 17:0, and trans-16:1n7) were inversely associated with risk for T2D. In the most adjusted model, the HR for incident T2D (per cohort-specific 10th to 90th percentile range) was 0.80 for 15:0 (95% CI, 0.73-0.87), 0.65 for 17:0 (95% CI, 0.59-0.72), 0.82 for trans-16:1n7 (95% CI, 0.70-0.96), and 0.71 for their sum (95% CI, 0.63-0.79). The inverse association with T2D was found to be stronger in women than men for 15:0 (P =.0003), 17:0 (P =.003), and the sum of all 3 fatty acids (P =.0003), with women having a 20% to 27% lower risk compared with men.
Limitations to the study included the inability to distinguish between different food sources of dairy fat using biomarkers, which may have resulted in residual confounding. In addition, delayed timing of T2D diagnosis may have limited the study by causing a misclassification of timing in survival analysis.
The researchers found that higher levels of fatty acid biomarkers 15:0, 17:0, and trans-16:1n7 were inversely associated with risk for T2D. “These novel findings support the need for additional clinical and molecular research to elucidate the potential effects of these fatty acids on glucose-insulin metabolism and the potential role of selected dairy products for the prevention of T2D,” concluded the investigators.
Multiple authors declare associations with the pharmaceutical industry. Please see original reference for a full list of authors’ disclosures.
Imamura F, Fretts A, Marklund M, et al. Fatty acid biomarkers of dairy fat consumption and incidence of type 2 diabetes: A pooled analysis of prospective cohort studies [published online October 10, 2018]. PLoS Med. doi:10.1371/journal.pmed.1002670