Assessment of dietary fish consumption in pregnancy: comparing one-, four- and thirty-six-item questionnaires

Abstract

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.

Trial registration: ClinicalTrials.gov NCT01126762.

Conflict of interest statement

Disclaimer: None of the authors has a conflict of interest to report.

Figures

Figure 1

Bland-Altman plot comparing docosahexaenoic acid (DHA) intake assessed by 4-item and 36-item food frequency questionnaires

Figure 2

Bland-Altman plot comparing mercury intake assessed by 4-item and 36-item food frequency questionnaires