Validation of two food frequency questionnaires for dietary calcium assessment

Easily utilized questionnaires estimating dietary calcium intake would be a valuable asset to promoting skeletal health as well as a helpful research tool. Two calcium questionnaires, one online and one printed, were each compared with dietary calcium intake measured by a 3-day diet record. Women completed the questionnaires in a randomized order and kept a 3-day food record at home, returning it by mail. The ethnicity of the 140 female study participants was 102 white, 12 African American, 16 Asian, and 10 Latina. The mean age (+/-standard deviation) was 49+/-15 years, with a range of 22.7 to 89.9 years. Measures used included an online calcium quiz, a printed calcium food frequency questionnaire, and one 3-day diet record. Data analysis was done using Pearson correlation coefficients. Sub-analyses were conducted by ethnicity. The correlation between each questionnaire and the daily calcium intake from the diet records was 0.37, P<0.001. Among the ethnic subgroups, the correlations were highest for African-American women, followed by white women. There was also a trend toward higher correlations in younger women. These simple calcium assessment tools, taking fewer than 5 minutes to complete, have correlation values with diet records similar to more complex food frequency questionnaires reported in the literature. These questionnaires may provide valuable tools to estimate calcium intake in research, clinical, and community settings.