Association between dietary fiber, water and magnesium intake and functional constipation among young Japanese women

Objective: Most research on constipation has focused on dietary fiber intake. Here, we examined the intake of water and magnesium, nutrients possibly associated with constipation, as well as that of dietary fiber in relation to constipation. Design: Cross-sectional study. Subjects: A total of 3835 female Japanese dietetic students aged 18 - 20 years from 53 institutions in Japan.] Methods: Dietary intake was estimated with a validated, self-administered diet history questionnaire. Functional constipation was defined using the Rome I criteria. Results: The prevalence of functional constipation was 26.2%. Neither dietary fiber intake (mean = 6.4 g/4186 kJ) nor intakes of total water and water from fluids were associated with constipation. Conversely, low intake of water from foods was associated with an increasing prevalence of constipation. In comparison with women in the first (lowest) quintile, the multivariate adjusted odds ratio (OR) (95% confidence interval (CI)) for women in the second, third, fourth, and fifth quintiles were 0.72 (0.57, 0.90), 0.78 (0.62, 0.98), 0.71 (0.56, 0.89), and 0.77 (0.61, 0.97), respectively (P for trend = 0.04). Additionally, low magnesium intake was associated with increasing prevalence of constipation. Compared with women in the first quintile, the multivariate adjusted OR (95% CI) for women in the second, third, fourth and fifth quintiles were 0.70 (0.56, 0.88), 0.75 (0.60, 0.95), 0.73 (0.58, 0.92) and 0.79 (0.63, 0.996), respectively (P for trend = 0.09). Conclusions: Low intakes of water from foods and magnesium are independently associated with an increasing prevalence of functional constipation among a population whose dietary fiber intake is relatively low.