Red blood cell delta15N: a novel biomarker of dietary eicosapentaenoic acid and docosahexaenoic acid intake

Am J Clin Nutr. 2009 Mar;89(3):913-9. doi: 10.3945/ajcn.2008.27054. Epub 2009 Jan 28.


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.

Design: 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Age Factors
  • Alaska
  • Biomarkers / blood
  • Cross-Sectional Studies
  • Dietary Fats / administration & dosage
  • Dietary Fats / blood*
  • Docosahexaenoic Acids / administration & dosage
  • Docosahexaenoic Acids / blood*
  • Eicosapentaenoic Acid / administration & dosage
  • Eicosapentaenoic Acid / blood*
  • Erythrocytes / metabolism*
  • Female
  • Humans
  • Inuits
  • Linear Models
  • Male
  • Middle Aged
  • Nitrogen Isotopes / blood*
  • Sex Factors
  • Young Adult


  • Biomarkers
  • Dietary Fats
  • Nitrogen Isotopes
  • Docosahexaenoic Acids
  • Eicosapentaenoic Acid