Water UK

Introduction

Constipation can be defined in various ways such as the number of stools per day, ease of passage of the stool, abnormal faecal retention as well as changes in the volume, weight, or consistency of stools. Stools may be dry, hard and/or small and may be difficult to expel, sometimes with a sensation of incomplete evacuation.(1,2) In the UK about 10 per cent of adults reported constipation in the preceding two weeks.(3) Constipation is more frequent in incapacitated or institutionalised older people. In one study, 42 per cent of patients admitted to geriatric wards were diagnosed as constipated.(4)

Importance of adequate fluid intake

Inadequate fluid intake is thought to be one of the most frequent causes of chronic constipation. A relatively short period of fluid deprivation has been shown to decrease stool frequency and stool weight in healthy volunteers.(5)

In a larger study, men were found to have, on average, 9.9 bowel movements per week and 8.6 for women. Ninety three per cent of men and 83 per cent of women reported having daily bowel movements. The mean number of bowel movements per week steadily increased with increasing intake of water and juices for both men and women. Higher fluid intake also increased the odds of having daily bowel movements compared with the lowest fluid intake category. In addition to fluid intake, the study found that dietary fibre intake, vegetarian or vegan diet and vigorous exercise were also strongly associated with a higher frequency of bowel movements.(6) For individuals who are already constipated, the beneficial effects on stool frequency arising from a daily fibre intake of 25g have been shown to be significantly enhanced by increasing fluid intake to 1.5-2 litres per day.(7) Although extra fluid intake is often recommended to alleviate symptoms of constipation, additional fluids given to healthy, adequately hydrated, individuals who are not already constipated, has no effect on stool frequency.(8)

For older people, those who are better hydrated are less likely to experience constipation. One study found that 27 per cent of those drinking less than three glasses of fluid a day were constipated, as opposed to 15 per cent of those drinking three to five glasses and 11 per cent of those consuming six glasses.(9)

Children

In children, stool frequency varies with age. There is a general decrease from more than 4 stools per day during the first week of life, to 1.2 stools per day at the age of 4 years, at which time an adult pattern of bowel movement is established. Constipation is three times more common in prepubertal boys than girls, but this ratio reverses in adolescence. Chronic constipation is a very common complaint in childhood. Estimates range from 3-8 per cent of the paediatric population. Inadequate fluid intake or excessive fluid loss from diarrhoea, vomiting or febrile illness may lead to hardening of the stool and are important causes of constipation, especially in infants. In addition, children may be susceptible if they neglect the urge to defaecate because it interferes with activities such as playing, and this may promote impaction. For simple constipation, behavioural training and dietary changes such as an increased fluid and fibre intake are recommended.(1)

In children aged 2-12 years who were adequately hydrated, however, a 50 per cent increase in water intake had no effect on daily stool frequency, consistency and difficulty with passage. This suggests that increased fluid intake is not beneficial in treating adequately hydrated children with constipation. Increased fluid consumption should only be considered if the child has a lower-than-normal fluid intake for their age and activity level. However, the absence of tools to adequately assess hydration status in children hampers the ability to determine the effects of minor modifications in fluid intake on stool consistency in constipated children.(10)

Conclusions

Dehydration of the colonic contents will harden stool consistency and increase constipation. However, increasing fluid intake for adults and children who are not dehydrated does not appear to be beneficial in treating constipation. In adults and elderly subjects, such dehydration may be due to poor intake of water, or excessive loss of fluid and electrolytes from the body during illness, eg vomiting, high sweating rates or from renal disease. In children, inadequate fluid intake, diarrhoea, febrile illness and neglecting the urge to defaecate may be important causes. It is important to maintain good hydration levels in order to help prevent constipation.(1,11) The prevention of constipation is also important in relation to healthy lifestyles because it has been identified as a risk factor for colorectal cancer.(12)

(see also Cancer)

Last updated: December 2006

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(2) Ritz P and Berrut G. The importance of good hydration for day-to-day health. Nutr Rev 2005;63:S6-S13
(3) Murtag J. Constipation. Aust Fam Physician 1990;19:1693-1697
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(10) Young RJ, Beerman LE and Vanderhoof. Increasing oral fluid in chronic constipation in children. Gastroenterol Nurs 1998;21:156-61
(11) Manz F and Wentz A. The importance of good hydration for the prevention of chronic diseases. Nutr Rev 2005;63:S2-S5
(12) Sonnenberg A, Muller AD. Constipation and cathartics as risk factors of colorectal cancer: a meta-analysis. Pharmacology 1993;47(Suppl 1):224-33