Persistent Diarrhoea

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Diarrhoea is a risk factor for the development of nutritional deficiencies and nutrients that are most likely to become deficient depends upon the cause as well as the degree for diarrhoea.

Even acute infective diarrhoea for more than 24 hours can lead to a loss of potassium and sodium that may need to be specifically replaced especially in the frail and those at the extreme ages of life.

Diarrhoea is defined as “the abnormal passage of loose or liquid stools more than three times per day and/or an amount of stool greater than 200 g/day. “  Guidelines for the investigation of chronic diarrhoea, 2nd edition. Gut 2003;52 (Suppl V):v1-v15 www.bsg.org.uk/pdf_word_docs/cd_body.pdf

Estimates of the prevalence of chronic diarrhoea in a western population are of the order of 4% to 5% and may be twice this amongst the elderly.   Not all diarrhoea will result in nutritional deficiencies developing but this will be more likely if there is any associated unintentional weight loss or other risk factors are present. 

The above expert guidance for investigation includes measurement of full blood count for anaemia and measures of iron, calcium, vitamin B12 and folate status as standard in patients with chronic diarrhoea.  The presence of proven nutritional deficiencies should prompt further definitive investigation as well as leading to appropriate nutrition support.

Common Causes of Diarrhoea and Nutritional Consequences

Only the main nutritional deficiencies are listed.

• Coeliac disease – iron, folate, iron, zinc, calcium and many other deficiencies
• Ulcerative colitis – iron, especially if bleeding, calcium (osteoporosis)
• Crohn’s disease – iron, vitamin B 12, zinc and calcium (osteoporosis)
• Colonic cancer – iron if bleeding develops
• Small bowel disease – many nutrients depending upon the cause
• Following bowel resection – calcium, fat soluble nutrients and many others
• Lactose intolerance – calcium leading to an increased risk of osteoporosis
• Pancreatic disease – vitamins A, D, E, K, B12, zinc, calcium and others
• Bile acid malabsorption – possibly fat soluble vitamins and calcium
• Persistent antibiotic use – vitamin K
• Alcohol excess – vitamin B1 – thiamine, folate and zinc and most other nutrients
• Endocrine causes – sodium, potassium and other nutrients depending upon the cause
• Excessive use of laxatives – potassium

Those with acute diarrhoea may well need nutritional support see Nutritional Emergencies - Persistent Diarrhea.

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