Fluid Intake and Dietary Factors and the Risk of Incident Kidney Stones in UK Biobank: A Population-based Prospective Cohort Study

Background: Fluid intake and diet are thought to influence kidney stone risk. However, prospective studies have been limited to small samples sizes and/or restricted measures.

Objective: To investigate whether fluid intake and dietary factors are associated with the risk of developing a first kidney stone.

Design, setting, and participants: Participants were selected from UK Biobank, a population-based prospective cohort study.

Outcome measurements and statistical analysis: Cox proportional hazards models were used to investigate the association between fluid intake and dietary factors and the risk of a first incident kidney stone, ascertained from hospital inpatient records.

Results and limitations: After exclusion, 439 072 participants were available for the analysis, of whom 2057 had hospital admission with an incident kidney stone over a mean of 6.1 yr of follow-up. For every additional drink (200 ml) consumed per day of total fluid, the risk of kidney stones declined by 13% (hazard ratio [HR] = 0.87, 95% confidence interval [CI] 0.85-0.89). Similar patterns of associations were observed for tea, coffee, and alcohol, although no association was observed for water intake. Fruit and fibre intake was also associated with a lower risk (HR per 100 g increase of fruits per day = 0.88, 95% CI 0.83-0.93, and HR per 10 g fibre per day = 0.82, 95% CI 0.77-0.87), whereas meat and salt intake was associated with a higher risk (HR per 50 g increase in meat per week = 1.17, 95% CI 1.05-1.29, and HR for always vs never/rarely added salt to food = 1.33, 95% CI 1.12-1.58). Vegetable, fish, and cheese intake was not associated with kidney stone risk.

Conclusions: The finding that high intake of total fluid, fruit, and fibre was associated with a lower risk of hospitalisation for a first kidney stone suggests that modifiable dietary factors could be targeted to prevent kidney stone development.

Patient summary: We found that higher intake of total fluid, specifically tea, coffee, and alcohol (but not water), and consumption of fruit and foods high in fibre are linked with a reduced likelihood of developing kidney stones.