Diarrhea and Diet

What is diarrhea?

Diarrhea is defined as the frequent passage of watery, loose stools, accompanied by an excessive loss of fluid and electrolytes. Another standard definition of diarrhea is passing more than three liquid bowel movements daily, or more than one litre of stool from an ileostomy or colostomy per day. Diarrhea occurs because the contents of the gastrointestinal tract are moving too rapidly, causing less fluid and nutrients to be absorbed.

What causes diarrhea?

Diarrhea is classified into four categories: osmotic, secretory, exudative, or rapid intestinal transit diarrhea.

Osmotic diarrhea is caused by the presence of solutes in the gastrointestinal tract that are poorly absorbed and produce an osmotic effect. The osmotic effect is the movement of water from low solute concentration to high solute concentration. The causes of osmotic diarrhea may be lactose intolerance, fat malabsorption, dumping syndrome after gastric surgery, or certain medications (i.e. hypertonic or sorbitol-containing liquid medications).

Secretory diarrhea occurs when there is an over secretion of water and salts in the intestine, which is caused by bacterial toxins (Clostridium difficile, E. coli, etc.), caffeine, viruses, or increased bile acids following an ileal resection.

Exudative diarrhea is associated with damage to the intestinal mucosa, leading to the release or oozing of mucus, blood, and plasma proteins from cells as result of inflammation or injury. This increases the fluid content of feces and is present in ulcerative colitis, Crohn’s disease, or radiation enteritis.

Finally, rapid intestinal transit diarrhea is defined as an increase in propulsive activity in the colon. When the colon contracts more intensely than normal, food is passed more quickly through the digestive system and less water is absorbed back into the body, making the stool too watery. Causes of this type of diarrhea are irritable bowel syndrome, surgical bypass, gastric and intestinal resections, antibiotics, or stress.

How can diarrhea be prevented?

Prevention of diarrhea depends on the underlying cause. If medications are causing a person to experience diarrhea, an alternative form (i.e. tablet instead of sorbitol-containing liquid) or type of medication should be explored, especially when diarrhea is chronic. Some people who are malnourished or on bowel rest, may experience diarrhea for the first few days when starting to eat again because the bowel wall’s ability to function decreases when it is not used and resumes normal function slowly. Consult your physician to determine the underlying cause and treatment for your diarrhea, especially if there is any associated pain, blood, or distension.

Dietary Recommendations for Diarrhea:

  • Drink 8-10 cups of fluid per day, like water, broth, half-strength juice, weak tea, or electrolyte replacement drinks.
  • Eat small frequent meals slowly during the day.
  • Try sources of soluble fibre to help firm up stool.
  • Limit fried or fatty foods since these can worsen diarrhea.
  • Some high fibre foods may contribute to diarrhea.
  • Foods with lots of sugar may worsen diarrhea, such as regular pop, candy, large quantities of juice, and chocolate milk.
  • Some people may become temporarily lactose intolerant when experiencing diarrhea (so can benefit from lower lactose choices, such as cheese, yoghurt, Lactaid® milk or Lactaid® pills).
  • Consult your physician to determine if an anti-diarrheal medication is suitable for you.

The following foods may be better tolerated:

Fruits and Vegetables Applesauce, apples, bananas, peaches, apricots, canned pears, grapefruit, potatoes, melons, squash
Breads and Cereals Oatmeal, oat bran, white rice, plain noodles, white bread/bagels, crackers, cream of wheat, arrowroot cookies
Protein foods Cheese (especially low fat), yoghurt, eggs, lean fish, beef, pork, skinless poultry

Foods to limit:

Fruits and Vegetables Prunes, prune juice, berries, dates, any dried fruit, figs, rhubarb, green beans, wax beans, peas, Brussels sprouts, corn, broccoli
Breads and Cereals Whole wheat, bran products, Shreddies, Mini Wheat, Raisin Wheat, Shredded Wheat, Bran Flakes, bulgur, Wheetabix, All Bran, Bran Buds, barley, Red River, wheat germ, Muslix
Protein foods Dried beans, dried peas, lentils, nuts and seeds, and fried meats, fish, and poultry


Mary Flesher, Clinical Dietitian
First published in the Inside Tract® newsletter issue 139 – September/October 2003
Image: Tharakorn | bigstockphoto.com