According to a study by Nestlé Water Institute on dehydration, and constipation, the most important factors known to promote constipation are reduced physical activity and inadequate dietary intake of fiber, carbohydrates and fluids. Fluid losses induced by diarrhea can alter water balance and promote constipation.
The study also found when children increase their water consumption above their usual intake there is no change in stool frequency and consistency. The improvement of constipation by increasing water intake only occurred when the initial fluid consumption was lower than normal for the child’s age and activity level. In the elderly, low fluid intake, which may be indicative of dehydration, was considered a cause of constipation. There was a significant relationship between lower than normal fluid intake and constipation.
Dehydration is also observed when saline laxatives are used for the treatment of constipation if the lost fluids are not replaced. Interestingly, magnesium sulphate-rich mineral waters were shown to improve constipation in healthy infants. In summary fluid loss and dehydration increases constipation. However, drinking more than the normal amount of fluids intake appear to have no effect.