A short food frequency questionnaire to assess intake of seafood and n-3 supplements: validation with biomarkers

Background: Seafood intake is associated with beneficial effects for human health. Seafood provides a number of nutrients beyond the traditionally known long chain marine n-3 fatty acids EPA, DPA and DHA, such as protein, vitamin D, iodine, selenium and vitamin B-12. Valid assessment of dietary seafood and n-3 supplement intakes are becoming increasingly crucial when giving recommendations to populations as seafood consumption is regarded as an important part of a healthy and balanced diet. Methods: The aim was to validate a short FFQ developed for assessment of dietary intake of seafood and n-3 supplements using the biomarkers marine n-3 fatty acids in erythrocytes and 25(OH) D in serum. Results: Fifty-three healthy Norwegians aged 30-64 years with a mean BMI of 25 kg/m(2) were compliant with the study protocol. 70% reported eating seafood for dinner one to two times per week, and 45% reported to eat seafood as spread, in salads or as snack meal three to five times or more per week. The FFQ correlated significantly with both the levels of marine n-3 fatty acids (r = 0.73, p < 0.0001) and with 25(OH) D (r = 0.37, p < 0.01). Mean level of marine n-3 and of 25(OH) D were 232 +/- 65 mu g/g erythrocytes and 73 +/- 33 nmol/L serum, respectively. Conclusion: The present short FFQ predicted strongly the levels of marine n-3 fatty acids in erythrocytes, and predicted fairly good the level of serum 25(OH) D and may therefore be a valid method for assessment of seafood and n-3 supplements intake among adults.