Circulating fatty acids as biomarkers of dairy fat intake: data from the lifelines biobank and cohort study.

C14:0, C15:0, C17:0 and trans-C16:1(-7) are often used as biomarkers for dairy fat intake. Trans-C18:1(-7) and CLA, two fatty acids which are also present in dairy, have hardly been explored. We investigated whether trans-C18:1(-7) and CLA can enrich the existing biomarker portfolio. Data were obtained from Lifelines ( = 769). Dairy fat intake was determined by FFQ. Fatty acids were measured in fasting plasma triglycerides (TG), phospholipids (PL) and cholesterol esters (CE). Median (25th-75th percentile) intakes of dairy and dairy fat were 322(209-447) and 12.3(8.4-17.4) g/d respectively. A pilot study showed that trans-C18:1(-7) and CLA were only detectable in TG and PL. Of the established markers, TG C15:0 was most strongly associated with dairy fat intake (standardized β (std.β) = 0.286,  = 0.111). Of the less established markers, TG trans-C18:1(-7) was most strongly associated with dairy fat intake (Std.β = 0.292,  = 0.115), followed by PL CLA (Std.β = 0.272,  = 0.103) and PL trans-C18:1(-7) (Std.β = 0.269,  = 0.099). In TG, a combination of C15:0 and trans-C18:1(-7) performed best ( = 0.128). In PL, a combination of C14:0, C15:0, trans-C18:1(-7) and CLA performed best ( = 0.143). Trans-C18:1(-7) and CLA can be used as biomarkers of dairy fat intake. Additionally, combining established with less established markers allowed even stronger predictions for dairy fat intake.