Fatty acids as biomarkers for health status and nutritional intake: focus on dairy and fish

The main goal of this thesis was to explore commonly (C14:0, C15:0, C17:0 and Trans-C16:1(n-7)) and less commonly (Trans-C18:1(n-7) and Conjugated linoleic acid (CLA)) investigated fatty acid biomarkers for dairy and dairy fat intake in the general population. We therefore developed a new method, with which we would be able to measure all potential biomarkers. We also explored whether the association between dairy fat biomarkers and dairy fat intake was independent of fish fat intake, since it has been suggested that C15:0 and C17:0 might also be biomarkers for fish intake. It appeared that C14:0, C15:0, C17:0, trans-C16:1(n-7), trans-C18:1(n-7) and CLA are useful biomarkers of dairy fat intake for the general population. Moreover, we found that a combination of commonly and less commonly fatty acids was the best predictor for dairy fat intake. Associations of dairy biomarkers with dairy fat intake were independent of fish fat. C15:0, trans-C18:1(n-7) and CLA were found to be inversely associated with cardiovascular risk factors. Literature shows that the marine-derived omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid are also inversely related to cardiovasclular risk factors. This thesis shows that this is might also be true in a renal transplant recipients. In contrast, in this population, the plant-derived omega-3 fatty acid alpha-linolenic acid may be associated with an increased risk of mortality.