a1 Department of Population Medicine, Harvard Medical School and the Harvard Pilgrim Health Care Institute, 133 Brookline Avenue, Boston, MA 02215, USA
a2 Department of Nutrition, Harvard School of Public Health, Boston, MA, USA
a3 Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA
a4 Department of Obstetrics and Gynecology, Harvard Vanguard Medical Associates, Boston, MA, USA
a5 Children's Hospital Boston, Boston, MA, USA
a6 Channing Laboratory, Brigham and Women's Hospital, Boston, MA, USA
Objective Fish consumption influences a number of health outcomes. Few studies have directly compared dietary assessment methods to determine the best approach to estimating intakes of fish and its component nutrients, including DHA, and toxicants, including methylmercury. Our objective was to compare three methods of assessing fish intake.
Design We assessed 30 d fish intake using three approaches: (i) a single question on total fish consumption; (ii) a brief comprehensive FFQ that included four questions about fish; and (iii) a focused FFQ with thirty-six questions about different finfish and shellfish.
Setting Obstetrics practices in Boston, MA, USA.
Subjects Fifty-nine pregnant women who consumed ≤2 monthly fish servings.
Results Estimated intakes of fish, DHA and Hg were lowest with the one-question screener and highest with the thirty-six-item fish questionnaire. Estimated intake of DHA with the thirty-six-item questionnaire was 4·4-fold higher (97 v. 22 mg/d), and intake of Hg was 3·8-fold higher (1·6 v. 0·42 μg/d), compared with the one-question screener. Plasma DHA concentration was correlated with fish intake assessed with the one-question screener (Spearman r = 0·27, P = 0·04), but not with the four-item FFQ (r = 0·08, P = 0·54) or the thirty-six-item fish questionnaire (r = 0·01, P = 0·93). In contrast, blood and hair Hg concentrations were similarly correlated with fish and Hg intakes regardless of the assessment method (r = 0·35 to 0·52).
Conclusions A longer questionnaire provides no advantage over shorter questionnaires in ranking intakes of fish, DHA and Hg compared with biomarkers, but estimates of absolute intakes can vary by as much as fourfold across methods.
(Received August 03 2012)
(Revised March 18 2013)
(Accepted May 08 2013)
(Online publication July 24 2013)