Development and validation of a calcium intake questionnaire for postmenopausal women in China

PURPOSE: Develop and evaluate a food frequency questionnaire (FFQ) for asse ssing calcium intake in Chinese postmenopausal women. METHODS: An interviewer-conducted FFQ that asks respondents about their con sumption of 110 calcium-containing foods over the previous week was develop ed and administered to 21 randomly selected postmenopausal women from Cheng du. This FFQ uses both the traditional weight-estimation method of assessin g portion size in China and a new volume-estimation method. Test-retest rel iability was assessed by re-administering the questionnaire two weeks later and validity was assessed by comparing the computed daily calcium intake t o that obtained by a researcher-conducted 4-day food record. RESULTS: Estimates of calcium intake derived from the volume-estimation met hod were significantly lower than estimates derived from the traditional we ight-estimation method (median calcium intakes = 270 mg/day versus 570 mg/d ay), but were quite similar to those obtained from the if-day food record ( median calcium intake = 275 mg/day). The test-retest reliability and validi ty of the volume-estimation method (intraclass correlation coefficient (ICC ) = 0.73 and 0.86, respectively) were better than those of the weight-estim ation method (ICC = 0.58 and 0.39, respectively). CONCLUSIONS: The reliability and validity of the traditional weight-estimat ion FFQ method of assessing dietary intake of nutrients in China is poor; t his method may significantly overestimate dietary intakes. The proposed vol ume-estimation FFQ method for assessing calcium intake is a simple, intervi ewer-conducted method that is both reliable and valid. The calcium intake o f postmenopausal women in urban China is much lower than the recommended da ily allowance of 800 mg. Ann Epidemiol 2000;10:169-175. (C) 2000 Elsevier S cience Inc. All rights reserved.