Biomarker and dietary validation of a Canadian food frequency questionnaire to measure eicosapentaenoic and docosahexaenoic acid intakes from whole food, functional food, and nutraceutical sources.

BACKGROUND

Canadian dietary sources of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) include marine and non-marine whole foods, functional foods, and nutraceuticals.

OBJECTIVE/DESIGN: In the present study, these sources were incorporated into a nutrient-specific, semi-quantitative food frequency questionnaire (FFQ) and the ability to measure the EPA and DHA intakes of Canadian adults was assessed. Specifically, the EPA and DHA intakes estimated by FFQ of 78 men and women, 20 to 60 years of age, were compared with EPA and DHA measurements from 3-day food records and measures of EPA and DHA in fasting whole blood.

RESULTS

Mean (±standard deviation) and median intakes of EPA+DHA were 0.34±0.34 and 0.21 g/day by FFQ and 0.47±0.71 and 0.13 g/day by food record, with no significant differences between mean intakes (P=0.93). The FFQ provided higher estimates than the food record at low intakes of EPA and DHA and lower estimates at high intakes based on Bland-Altman plots. The FFQ was moderately correlated with food record (r=0.31 to 0.49) and with blood biomarker measures of EPA and DHA (r=0.31 to 0.51). Agreement analysis revealed that 42% of participants were classified in the same and 77% into same or adjacent quartile when EPA and DHA intake was assessed by food record and by FFQ. Similar quartile agreement was found for EPA and DHA intakes by FFQ with blood biomarker EPA and DHA. The range of the validity coefficients, calculated using the method of triads, was 0.43 to 0.71 for FFQ measurement of EPA+DHA.

CONCLUSIONS

The FFQ is an adequate tool for estimating usual EPA and DHA intakes and ranking Canadian adults by their intakes.