Questionnaire assessment of antioxidants and retinol intakes in Mexican women

Background. In order to assess intake of antioxidants and retinol, we evalu ated the validity and reproducibility of a semiquantitative food frequency questionnaire. Methods. Data were collected from 110 women, aged 15-54 years, who resided in the southern part of Mexico City, Study participants were asked to compl ete the food frequency questionnaire before and after completing four serie s of 4 days of 24-h diet recalls. We obtained the 24-h recalls at 3-month i ntervals designed to account for seasonal variability. In addition, we meas ured serum blood levels of retinol and various carotenoids at 3 and 9 month s after baseline. Results. Intraclass correlation coefficients for intake of energy-adjusted daily nutrients, assessed by the questionnaires 1 year apart, ranged from 0 .23 for lutein/zeaxanthin to 0.50 for total carotenes. Correlation coeffici ents between energy-adjusted nutrient intakes were measured by means of the sixteen 24-h dietary recalls, and the second questionnaire ranged from 0.0 9 for lutein/zeaxanthin Co 0.45 for total carotenes. These correlations wer e higher after adjusting for day-to-day variations in diets ranging from 0. 11 for lutein/zeaxanthin to 0.49 for vitamin C. Correlation coefficients be tween intake and biochemical measures were 0.32 for alpha-carotene, 0.34 fo r beta-carotene, and 0.40 for total carotene after adjusting for age, body mass index, cholesterol and triglyceride plasma levels, smoking status, and caloric intake. Conclusions. These data support the ability of our food frequency questionn aire to provide valid information on the relative intake of these nutrients and to confirm its usefulness in epidemiological studies of diet-disease r elations. However, its application outside Mexico City or in different age or gender populations will require additional modifications and validation efforts. (C) 1999 IMSS. Published by Elsevier Science Inc.