Biomarkers for dietary fatty acid densities among postmenopausal United States females derived using a habitual-diet human feeding study

BACKGROUND: Although measures of blood and tissue fatty acid (FA) concentrations are available, objective measures of dietary FA densities (grams per kilocalories) are generally lacking. OBJECTIVES: We aimed to explore the development of biomarkers for specific and composite dietary FA densities, not including contributions from dietary supplements, using metabolite profiles from serum and 24-h urine, along with separately measured serum phospholipid FA concentrations in the Women's Health Initiative. METHODS: Potential biomarker equations were based on linear regression of feeding study dietary FA densities on metabolite concentrations, each log-transformed, among participants in a habitual-diet human feeding study (n = 153) within the Women's Health Initiative. Corresponding biomarker equations were also considered for total SFA, MUFA, and PUFA densities and for total n-3 and n-6 PUFA densities. Dietary FA density estimates derived from these equations were evaluated by correlation with feeding study intake densities, and by other important biomarker criteria. RESULTS: values >30% for specific SFAs were 64.7 butyric, 60.9 caprioc, 48.7 caprylic, 53.0 capric, 39.9 lauric, 61.0 myristic, 42.2 palmitic, 34.2 stearic, 34.8 arachidic, 49.9 decosanoic; for specific MUFAs were 31.3 oleic; and for specific PUFAs were 51.7 linoleic, 50.1 α-linolenic, 39.7 arachidonic, 40.2 EPA, 53.5 decosapentaenoic acid, and 47.9 DHA. Corresponding values were 46.4, 52.8, 46.1, and 52.4 for total SFA, total PUFA, total n-3, and total n-6 densities. Many FA density equations had contributions from multiple metabolites, mostly serum metabolites, and from total energy expenditure. Sensitivity and specificity criteria are plausibly satisfied for proposed biomarkers, based on the feeding study design and on the sets of selected metabolites. CONCLUSIONS: Combinations of log-transformed metabolite concentrations can lead to objective intake density estimates for multiple FAs in the diets of United States postmenopausal females, with relevance to the reliable study of dietary FA densities and chronic disease risk. This study was registered at clinicaltrials.gov as NCT00000611 https://clinicaltrials.gov/study/NCT00000611).