Evaluation of an Updated Version of the Food Frequency and Sun Exposure Questionnaire for Assessing Vitamin D Status in Active Population

Abstract

Accurately assessing vitamin D intake is challenging because it can be obtained from both dietary sources and sun exposure. Food Frequency Questionnaires (FFQs) are one of the common methods used to estimate dietary intake. PURPOSE: Develop and validate the semiquantitative Food Frequency and Lifestyle Questionnaires (FFLQs) for assessing vitamin D intake using the method of triads which compare vitamin D intake with serum 25-hydroxyvitamin D (25(OH)D and vitamin D intake from food records in athletes. METHODS: Forty-one participants completed a semiquantitative FFLQ, 3-day or 4-day food records, and had blood drawn for analysis of serum 25(OH)D. The FFLQ evaluated vitamin D consumption from foods, supplements, food plus supplements, and lifestyle factors, including sun exposure, sunscreen, and outdoor activities. Statistical analyses including paired t-tests, Spearman Rank Correlation, and Bland-Altman analysis were applied to determine the agreement and correlation between the FFLQ, food records, and serum 25(OH)D concentrations. RESULTS: FFLQ-estimated Vitamin D intake was not correlated to serum total or free 25(OH)D concentrations. Total UV exposure showed a moderate association with total 25(OH)D concentrations (r = 0.43, P < 0.05). Day of year studies were moderately associated with free 25(OH)D concentrations (r = 0.41, P < 0.05) and showed weak correlation with total 25(OH)D (r = -0.34, P < 0.05). Additionally, leisure time and total UV exposure weakly correlated with free 25(OH)D concentrations (r = -0.33 and r = -0.39, P < 0.05). CONCLUSION: These findings suggest the importance of sun exposure in determining vitamin D concentrations. Further research, however, is needed to determine whether free 25(OH)D measurement is a useful biomarker of vitamin D status.