Validity of a questionnaire to assess fruit and vegetable intake in adults

Faculty of Nutrition and Food Sciences, University of Porto, Porto, PortugalObjective: To validate a method for assessing fruit and vegetable intake among adults in a population of low intake. The methodassesses mean intake and ranks individuals by their usual intake.Design: A precoded fruit and vegetable Questionnaire included a 24-h recall and a food frequency. The participants filled in theQuestionnaire, a week later they started a 7-day food record, 1-day weighed record and 6 days using household measures.Subjects: Following advertisements 40 participants were recruited, 36 returned food records(mean age¼37 years).Results: No difference was observed between the average intake yielded by the 24-h recall and that from the 1-day weighedfood record of fruits or vegetables. Correlation coefficients between results from the food frequency questionnaire and the 7-dayfood records were 0.45 (P¼0.007) for vegetables, 0.63 (Po0.001) for fruits and 0.73 (Po0.001) for fruits and vegetablescombined. Cross-classification into quartiles showed that the proportion of participants in the same or the adjacent quartile ofthe intake distribution were 94% for fruit intake and 80% for vegetable intake. Registered intake of fruits and vegetables washigher the first 4 days of the record than the last 3 days (P¼0.002). The 4-day food record correlated with the food frequencyquestionnaire in similar manner as the 7-day record.Conclusion: The present study indicates that the precoded 24-h recall may be valuable tool for measuring average intake offruits and vegetables among adults in a population of low intake. Moreover, the food frequency questionnaire was valid forranking individuals according to their usual intake. A 4-day food record might be sufficient when validating food frequencyquestionnaires for fruits and vegetables.European Journal of Clinical Nutrition (2006) 60, 408–415. doi:10.1038/sj.ejcn.1602332; published online 23 November 2005