"...all doctors should be able to diagnose and treat nutritional deficiencies."

Royal College of Physicians. Nutrition and Patients: A Doctor's Responsibility. London 2002


This page has been printed from the www.stewartnutrition.co.uk web site.

Prolonged Diarrhoea in Adults

Diarrhoea in adults is defined as passing more than 3 stools per day which typically are loose or watery and are usually more than 200 g in weight over 24 hours.

Acute Diarrhoea and Dehydration

The common causes of acute diarrhoea include infection with a virus or bacteria, consumption of spoiled food, consumption of alcohol or coffee to excess, intolerance to milk sugar (lactose) and sometimes other foods, coeliac disease (intolerance to wheat and other cereals) and a variety of medical problems and drugs. The most important immediate consequence of acute diarrhoea is dehydration and children, the elderly, those of petite build and those with co-exisiting medical problems are particularly vulnerable.

The symptoms of dehydration include thirst, dry mouth, loss of skin tone, a fall in blood pressure, reduced sweating, increased fever – if infection is present, confusion and reduced urine output.  This latter feature is often a dependable sign and a good urine output means that it is unlikely the individual is under-supplied with fluid.

In the UK many episode of acute diarrhoea will settle spontaneously within 24 to 48 hours and simply require the sufferer to drink water or dilute fruit juice frequently.  Those who are more seriously affected especially infants, children and the elderly may need to make use of oral rehydration preparations.

Further excellent advice on the management of acute diarrhoea is available from NHSDirect www.nhsdirect.nhs.uk

Diarrhoea that has persisted for more than a few days or is associated with significant weight loss e.g. >3kg in a 60 kg person or is accompanied by significant symptoms e.g. vomiting, fever, blood in the stool, abdominal pain, skin rash, arthritis or other symptoms of inflammation requires immediate medical assessment.

Prolonged Diarrhoea and Dietary Advice

Some of the common causes of infectious diarrhoea including Salmonella and Campylobacter may take two weeks to resolve.  Those with Prolonged diarrhoea from any cause will be at risk of nutritional deficiencies developing if little or no food is consumed.

Once the person is regularly tolerating fluids by mouth and is no longer dehydrated they should be ready to eat some food.   After three or four days without food the supply of nutrients to the cells lining the gut, the mucosa, will have fallen substantially.  These cells have a short, busy lifespan and a very high demand for nutrients and cautious early feeding may aid their recovery and help to curtail more Prolonged diarrhoea.

The World Health Organisation and other expert bodies recommend the BRAT regime which includes: 

  • Bananas (ripe and mashed)
  • Rice (white and cooked)
  • Apple (stewed with a little added sugar)
  • Tea (weak and black with added sugar). 

Bananas and apples are rich in potassium and contain easy to digest carbohydrate.  Additionally banana is rich in amylase-resistant starch, which may be of benefit to the gastrointestinal mucosa, cells that line the internal gut wall. 

Rice is a very easy to digest form of carbohydrate and rehydration regimes based upon rice have been shown to help diarrhoea due to cholera but not necessarily other types of infective diarrhoea.

Apples are easy to digest especially once cooked.  They contain fructo-oligosaccharides that may help to promote the growth of healthy bacteria in the bowel.  Bramley cooking apples, even once cooked, are exceptionally high in vitamin C, which is often mildly deficient in the ill frail elderly.  Adding sugar provides useful easy-to-assimilate energy.  Once made stewed apple should be kept in the fridge.

Tea helps to slow down the gut and avoiding milk will help to reduce the risk of the diarrhoea persisting due to (acquired) lactose intolerance. 

Some advisers replace Tea with Toast in the above regime in which case quality white bread is probably the preferred choice.  In the UK white flour is fortified with vitamins B1 – thiamine and B3 – niacinamide both of which may be important in speeding convalescence.  High fibre breads should be tried after white has been tolerated for a few days.

Spinach is one further food which could be usefully added at this stage.  This green leafy vegetable is exceptionally high in folate, another B vitamin for which the gut lining has a high requirement.  Drug-induced folate deficiency has been reported to result in atrophy (shrinkage) of the duodenal mucosa and diarrhoea.   Deficiency in the UK is common in adults, the elderly and heavy alcohol consumer but rare in infants. Other good sources include all green leafy vegetables, oranges, Flora ™ margarine and fortified breakfast cereals.  These latter also contain iron which may upset the gut and could theoretically promote the growth of some undesirable bacteria and so should be used with caution.

After a few days a more normal diet can be introduced with an emphasis on easy-to-digest protein including eggs, fish, bread, particularly white, potatoes and vegetable soup.  Prolonged adherence to the BRAT regime in infants has been associated with malnutrition as it is low in protein.

Nutritional Supplements for Diarrhoea

A few nutritional supplements may be worth considering in those with diarrhoea

  • Zinc supplements are recommended by the World Health Organisation for children in developing countries with acute diarrhoea at a dose of 20 mg of zinc for 10 to 14 days for children over 6 months of age.  The use of a zinc supplement in nutritionally-compromised children helps to reduce the risk of subsequent infections occurring.  It’s value for adults is uncertain and supplements should not be given to those with vomiting or significant upper abdominal symptoms as they can cause gastric irritation
  • Probiotic preparations may help some types of diarrhoea including antibiotic associated diarrhoea especially in those who are elderly and undernourished as evidenced by a low plasma abumin or have a low sodium level and reduces the risk of developing Clostridium difficile diarrhoea.  The preparation that is worth considering is a milk-based drink that contained Lactobacillus casei, L. bulgaricus and Streptococcus thermophilus  It is uncertain how much benefit it is to more routine patients with Prolonged diarrhoea
  • Vitamin B is required particularly by the gut mucosa.  Vitamin B3, nicotinamide, if deficient is a cause of diarrhoea and this could occasionally be present in those who are malnourished, alcoholics and in association with some rare disorders.  A supplement of vitamin B complex 50 mg three times per day would then be appropriate.
  • Folic acid might be worth considering in elderly patients or those who have been heavy alcohol consumers.  A supplement of 400 ug twice daily for three weeks would be a reasonable choice.
  • Multivitamin and multimineral preparations for those who are at high-risk of undernutrition including the elderly, those who are underweight, BMI <20.0 kg/m2and associated medical problems especially anaemia, chronic chest or heart disease 
  • Avoidance of some nutritional preparations including iron, magnesium, large amounts of vitamin C > 1g/day and sometimes chewable or effervescent preparations that contain sorbitol or xylitol can precipitate or aggravate diarrhoea

The above supplements can be taken safely for up to four weeks but it is advisable to check with a doctor or nutritionist before embarking on longer term use and asses the presence of major contraindications to supplement use.

Prevalence of Deficiency of Nutrients that may be Compromised by Diarrhoea  

Zinc Deficiency
Plasma Zinc <10umol/l
Not measured
Not measured
Potassium Deficiency
Intake <LRNI
Folate Deficiency
Red Cell Folate < 350 nmol/l

Chronic Diarrhoea - Definition

Chronic diarrhoea is considered to affect 4-5% of adults in Western countries.  Medical advice on the assessment and treatment of chronic diarrhoea should always be sought and detailed guidelines on its investigation have been issued by the British Society of Gastroenterology.  They define it as "three or more stools per day that are loose or liquid and/or exceed 200 mls in volume (approximately 7 ounces in weight) and has persisted for more than four weeks, which usually suggests a non-infective cause unless there are other features.” Initial investigation of such patients includes taking a good history, examination and tests of Full Blood Count, Liver Function Tests, serum Calcium, serum vitamin B12, red cell folate, tests of iron status, thyroid function and coeliac serology.


www.bsg.org.uk/pdf_word_docs/cd_body.pdf  Thomas PD et al. Guidelines for the investigation of chronic diarrhoea, 2nd edition.  Gut 2003;52(Suppl V):v1-v15

Copyright Dr. Alan Stewart M.B.B.S.M.R.C.P. (UK)M.F. Hom.
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