Why do I sometimes get diarrhea after eating out?

Patricia Raymond, MD
I’m assuming that you aren’t munching at Aunt Minnie’s World of Ice Cream, which would obviously lead to diarrhea from lactose intolerance in 25% of Euro-Americans, but up to 75% of Native Americans, African Americans, Hispanic Americans, and Asian Americans.

Several other benign possibilities exist. If you have irritable bowel syndrome or have had your gallbladder discarded, the higher fat content of most restaurant meals (why did you suppose it tasted so good?) leads to diarrhea. In those with irritable bowel, the increased fat triggers the exaggerated gastro colonic reflex, causing the colon to generate propulsive waves and thus diarrhea. Stay put at the restaurant until the potty impulse occurs. Similarly, those without a gallbladder fail to generate a good bolus of bile to emulsify the fat, and enjoy their diarrhea via the post-cholecystectomy syndrome.

Bacterial food poisoning symptoms include nausea, vomiting, abdominal cramping, and diarrhea that come on within 48 hours of consuming contaminated food or drink and generally resolve quickly. Bacteria may invade the wall of the intestine, interfering with absorption of water and nutrients, or exude a toxin that directly causes the colon to release fluids. Be concerned if you’re immunocompromised (on chemotherapy, have an inflammatory bowel condition, are on steroids, have moderate to severe liver failure, or have HIV infection), have fevers, or have bloody diarrhea. If any of these are present, or if you feel dehydrated or have severe abdominal cramps, seek medical attention.

If you’ve been noshing at Grandpa Frank’s (Aged) Fish Shack, beware. Bacterial spoilage from under-refrigeration of finfish, such as tuna, mackerel, bonito, skipjack, mahi-mahi, and bluefish, may lead to scromboid poisoning from histamine production in the spoiled fish. Within two minutes to two hours after eating the fish, your symptoms may include rash, diarrhea, flushing of the face, sweating, headache, dizziness, and vomiting. In addition, you may experience burning or swelling of the mouth, abdominal pain, or a metallic taste. Most people have mild symptoms which resolve on their own within 12 hours. If you think you have this condition, seek medical attention immediately. Scromboid poisoning may be life threatening!

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.