Development and Validation of a Calcium Intake Questionnaire for Postmenopausal Women in China

PURPOSE: Develop and evaluate a food frequency questionnaire (FFQ) for assessing calcium intake in Chinese postmenopausal women. METHODS: An interviewer-conducted FFQ that asks respondents about their consumption of 110 calcium-containing foods over the previous week was developed and administered to 21 randomly selected postmenopausal women from Chengdu. This FFQ uses both the traditional weight-estimation method of assessing portion size in China and a new volume-estimation method. Test-retest reliability was assessed by re-administering the questionnaire two weeks later and validity was assessed by comparing the computed daily calcium intake to that obtained by a researcher-conducted 4-day food record. RESULTS: Estimates of calcium intake derived from the volume-estimation method were significantly lower than estimates derived from the traditional weight-estimation method (median calcium intakes = 270 mg/day versus 570 mg/day), but were quite similar to those obtained from the 4-day food record (median calcium intake = 275 mg/day). The test-retest reliability and validity of the volume-estimation method (intraclass correlation coefficient (ICC) = 0.73 and 0.86, respectively) were better than those of the weight-estimation method (ICC = 0.58 and 0.39, respectively). CONCLUSIONS: The reliability and validity of the traditional weight-estimation FFQ method of assessing dietary intake of nutrients in China is poor; this method may significantly overestimate dietary intakes. The proposed volume-estimation FFQ method for assessing calcium intake is a simple, interviewer-conducted method that is both reliable and valid. The calcium intake of postmenopausal women in urban China is much lower than the recommended daily allowance of 800 mg.