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This Article Full Text (Publish Ahead of Print[PDF]) All Versions of this Article: 90/6/1642    most recent ajcn.2009.28482v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nash, S. H Articles by O'Brien, D. M PubMed PubMed Citation Articles by Nash, S. H Articles by O'Brien, D. M Agricola Articles by Nash, S. H Articles by O'Brien, D. M

Relation between stable isotope ratios in human red blood cells and hair: implications for using the nitrogen isotope ratio of hair as a biomarker of eicosapentaenoic acid and docosahexaenoic acid^1,2,3,4

¹ From the Center for Alaska Native Health Research, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK (SHN, BBB, JSM, and DMO), and the Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA (ARK and IBK).

² The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the National Center for Research Resources or the National Institutes of Health.

³ Supported by a Center of Biomedical Research Excellence grant from the NIH NCRR (P20 RR16430) and NIH NIDDK R01DK07442.

⁴ Address correspondence to DM O'Brien, Institute of Arctic Biology, PO Box 757000, University of Alaska Fairbanks, Fairbanks, AK 99775-7000. E-mail: dmobrien{at}alaska.edu.

ABSTRACT

Background: The nitrogen isotope ratio (expressed as ¹⁵N) of red blood cells (RBCs) is highly correlated with the RBC long-chain –3 (n–3) fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Yup'ik Eskimos. Because ¹⁵N can also be measured in hair samples, it could provide a noninvasive, retrospective biomarker for EPA and DHA intakes.

Objectives: We investigated the agreement between ¹⁵N in hair and RBCs and then evaluated the relations between hair ¹⁵N and RBC EPA and DHA. We also assessed the agreement in carbon isotope ratios (¹³C) between hair and RBCs, because ¹³C has been proposed as a dietary biomarker in other populations.

Design: We assessed relations between hair and RBC ¹⁵N and ¹³C in a community-based sample of 144 Yup'ik Eskimos and examined the correlations between ¹⁵N and RBC EPA and DHA in a subset of these participants (n = 44).

Results: We showed a 1:1 relation with good agreement between hair and RBC ¹⁵N (r = 0.91) and ¹³C (r = 0.87). Hair isotope ratios were greater than RBC ratios by 1.5 for ¹⁵N and by 2.3 for ¹³C. There were strong correlations between hair ¹⁵N and RBC EPA and DHA (r = 0.83 and 0.84, respectively).

Conclusions: These results support the use of hair ¹⁵N values as a biomarker of EPA and DHA intakes. Because hair collection is noninvasive and the samples require no special processing, studies of EPA and DHA intakes in large populations could use biomarkers rather than self-reports to assess these fatty acids.

Received for publication July 31, 2009. Accepted for publication September 19, 2009.