Fatty acids as biomarkers of total dairy and dairy fat intakes: a systematic review and meta-analysis.

Context: Dairy intake in humans is commonly assessed using questionnaires, but the data collected are often biased. As a result, there is increasing interest in biomarkers of dairy fat. To date, there has been no overview of the fatty acids suitable for use as biomarkers of dairy fat intake. Objective: This systematic review and meta-analysis of observational studies was performed to identify circulating fatty acids as biomarkers of total dairy and dairy fat intakes in the general population. Data Sources: MEDLINE, Embase, and Web of Knowledge databases were searched for eligible studies published until June 2017. Study Selection: Articles were included when a correlation between circulating dairy fatty acids and intakes of total dairy and dairy fat was found, as measured by dietary assessment tools. Data Extraction: Two authors extracted data independently and assessed the risk of bias. An adapted form of the Newcastle-Ottawa Scale was used for quality assessment. Results: Data were pooled using the random-effects model. Meta-analysis revealed that the fatty acids in plasma/serum were significantly correlated with intakes of total dairy (C14:0 [r = 0.15; 95% CI, 0.11 - 0.18], C15:0 [r = 0.20; 95% CI, 0.13 - 0.27], and C17:0 [r = 0.10; 95% CI, 0.03 - 0.16] and dairy fat (C14:0 [r = 0.16; 95% CI, 0.10 - 0.22], C15:0 [r = 0.33; 95% CI, 0.27 - 0.39], C17:0 [r = 0.19; 95% CI, 0.14 - 0.25], and trans-C16:1n-7 [r = 0.21; 95% CI, 0.14 - 0.29). Conclusions: C14:0, C15:0, C17:0, and trans- C16:1n-7 were identified as biomarkers of total dairy and dairy fat intakes in the general population. In light of the suboptimal measurement techniques used in some studies, correlations with trans- C18:1n-7 and conjugated linoleic acid require further investigation.