Validation of a dietary vitamin D questionnaire using multiple diet records and the block 98 health habits and history questionnaire in healthy postmenopausal women in northern California.

Vitamin D deficiency is common in older women and can negatively impact bone status. A simple method by which clinicians and researchers can evaluate a patient's vitamin D dietary intake could help identify individuals at risk for vitamin D deficiency. This study was done to validate a short dietary vitamin D questionnaire. Postmenopausal women (n=122), with a mean age of 63.9 ± 7.8 years, completed a Brief Vitamin D Questionnaire (BVDQ), the Block Health History and Habits Questionnaire 1998 (BHHHQ98), a 3-day food record, and an evaluation of serum 25 hydroxyvitamin D (25[OH]D) levels. Data were analyzed using Pearson correlation coefficients, Wilcoxon signed ranks tests, and Bland-Altman analyses to compare the performance of the BVDQ to the BHHHQ98 and to the diet record. As assessed by the BVDQ, vitamin D intake averaged 178.7 ± 112.3 IU per day, correlating well with the Block HHHQ98 (r=0.51, P<0.001) and the 3-day food record (r=0.43, P<0.001). Compared with the food record, both the BVDQ and the BHHHQ98 overestimated dietary vitamin D intake by less than 100 IU/day. The two questionnaires performed nearly identically at all levels of vitamin D intake. Serum 25(OH)D was not related to vitamin D intake as measured by either the BVDQ or the BHHHQ98, but did correlate weakly with vitamin D intake from the 3-day diet record (r=0.20, P=0.04). The Brief Vitamin D Questionnaire correlated well with the longer and more intense dietary assessment methods, making it a simple and accurate instrument for assessing vitamin D intake.