title: Red blood cell delta15N: a novel biomarker of dietary eicosapentaenoic acid and docosahexaenoic acid intake.
abstract: BACKGROUND
  The long-chain omega-3 (n-3) fatty acids derived from fish, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are associated with a reduced risk of cardiovascular disease and other chronic diseases. Study of the associations between EPA and DHA intake and disease requires a valid biomarker of dietary intake; however, the direct measurement of tissue fatty acid concentrations is expensive and time consuming.
  
  
  OBJECTIVE
  Because the nitrogen stable isotope ratio ((15)N/(14)N, expressed as delta(15)N) is elevated in fish, we investigated whether delta(15)N is a valid alternative biomarker of EPA and DHA intake.
  
  
  METHODS
  We examined the relation between red blood cell (RBC) delta(15)N and RBC EPA and DHA in a community-based sample of 496 Yup'ik Eskimos with widely varying intake of n-3 fatty acids. We also assessed the correlation between delta(15)N and dietary EPA and DHA intake based on 24-h dietary recalls and 3-d food records completed by a subset of 221 participants.
  
  
  RESULTS
  RBC delta(15)N was strongly correlated with RBC EPA and DHA (r = 0.83 and 0.75, respectively). These correlations differed only modestly by sex and age class. RBC delta(15)N also correlated with dietary EPA and DHA intake (r = 0.47 and 0.46, respectively) and did not differ by sex and age.
  
  
  CONCLUSIONS
  The results strongly support the validity of RBC delta(15)N as a biomarker of EPA and DHA intake. Because the analysis of RBC delta(15)N is rapid and inexpensive, this method could facilitate wide-scale assessment of EPA and DHA intake in clinical and epidemiologic studies.
authors.affiliation: Center for Alaska Native Health Research, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA. ffdo@uaf.edu
authors.forename: Diane M
authors.initials: DM
authors.lastname: O'Brien
authors.forename: Alan R
authors.initials: AR
authors.lastname: Kristal
authors.forename: M Alyssa
authors.initials: MA
authors.lastname: Jeannet
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wilkinson
authors.forename: Andrea
authors.initials: A
authors.lastname: Bersamin
authors.forename: Bret
authors.initials: B
authors.lastname: Luick
mesh_terms: D000328:Adult; D000367:Age Factors; D000413:Alaska; D015415:Biomarkers / Q000097:blood; D003430:Cross-Sectional Studies; D004041:Dietary Fats / Q000008:administration & dosage / Q000097:blood*; D004281:Docosahexaenoic Acids / Q000008:administration & dosage / Q000097:blood*; D015118:Eicosapentaenoic Acid / Q000008:administration & dosage / Q000097:blood*; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006801:Humans; D004930:Inuit; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009587:Nitrogen Isotopes / Q000097:blood*; D012737:Sex Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; D004041:Dietary Fats; D009587:Nitrogen Isotopes; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid