Diarrhea

Diarrhea can occur when infection, inflammation, malabsorption, medication, or irritants increase the amount of fluid in the bowel or speed transit. Acute diarrhea is usually infectious or food-poisoning related. Chronic or recurrent diarrhea (more than four weeks) is almost always worth investigating, and diet is one of several factors to consider.

A common diet-related mechanism is osmotic: poorly absorbed sugars and sugar alcohols pull water into the bowel, producing loose stools. Lactose, fructose, sorbitol, and mannitol are common culprits. Another mechanism is gut irritation — coffee, alcohol, and very spicy foods can accelerate motility to the point of producing loose stools in sensitive individuals. Bile acid issues, motility disorders, and medication side effects are other non-osmotic contributors worth ruling out clinically when symptoms persist.

Common food triggers

Lactose in adults with reduced lactase activity. Fructose in people with fructose malabsorption — apples, pears, mangoes, and agave are common triggers. Sugar alcohols (sorbitol, mannitol, xylitol) in sugar-free gum and candy. Artificial sweeteners in some people. Caffeine, which speeds gut motility. Alcohol, which irritates the gut lining. High-FODMAP foods in IBS-D (diarrhea-predominant IBS). Gluten in celiac disease and non-celiac gluten sensitivity.

When to investigate further

Acute diarrhea that lasts more than 48 hours, comes with high fever, severe pain, blood in stool, or signs of dehydration should be evaluated promptly. Chronic diarrhea warrants a workup for celiac disease, IBD, microscopic colitis, and other conditions before assuming it's diet-only. Always replace fluids and electrolytes.