Several common foods, drinks, and supplements can make diarrhea worse by pulling extra water into your intestines, speeding up gut contractions, or irritating an already inflamed digestive lining. The biggest culprits are sugary drinks, fatty foods, caffeine, dairy, and certain supplements. Knowing what to avoid can shorten a miserable few days considerably.
Sugary Drinks and Fruit Juice
Sodas, fruit juices, and sports drinks sweetened with high-fructose corn syrup are some of the worst things you can consume during a bout of diarrhea. Fructose is poorly absorbed even in healthy people, and unabsorbed sugar draws water into the intestines through osmosis, making stools more watery and frequent. In one controlled study, when healthy adults consumed about 50 grams of fructose (roughly the amount in two 12-ounce cans of regular soda), 80% showed signs of fructose malabsorption, and about half reported bloating or diarrhea. Products made with agave syrup are even more concentrated in fructose, with fructose making up about 84% of the carbohydrate content.
Apple juice is a particularly common offender because it’s naturally high in both fructose and sorbitol. If you’re thirsty, plain water or an oral rehydration solution with balanced electrolytes is a much safer choice.
Sugar-Free Gum and “Diet” Products
Sugar alcohols like sorbitol, mannitol, maltitol, and xylitol are used as sweeteners in sugar-free gum, mints, candies, and protein bars. Your small intestine absorbs them poorly, so they travel to the colon and pull water in behind them, the same osmotic mechanism that makes fructose a problem. Sorbitol causes gas, cramping, urgency, and watery stools in a dose-dependent way, with symptoms starting at as little as 5 grams per day. A few sticks of sugar-free gum can reach that threshold quickly. Research has documented cases of chronic, unexplained diarrhea that resolved completely once patients stopped chewing sugar-free gum.
Caffeine
Coffee, energy drinks, and strong tea stimulate muscle contractions along the digestive tract. Caffeine triggers nerve cells in the gut wall to release calcium from internal stores, which causes the smooth muscle to contract. At the concentrations you’d get from a couple of cups of coffee, that means faster transit through the intestines, giving your colon less time to absorb water from stool. If your gut is already irritated, caffeine amplifies the problem. Decaf coffee also stimulates the gut to some degree (coffee contains other compounds besides caffeine that affect motility), but the effect is weaker.
Fatty and Greasy Foods
High-fat meals trigger your liver to release more bile into the small intestine. Normally, bile acids get recycled at the end of the small intestine, but when your gut is inflamed or moving too fast, excess bile spills into the colon. Once there, bile acids irritate the lining, causing it to secrete extra fluid and speeding up the contractions that push stool along. This is the reason greasy takeout or fried food can turn mild diarrhea into something significantly worse. Stick with lower-fat options until things settle down.
Dairy Products
Even if you normally tolerate milk and cheese, a stomach bug can temporarily knock out your ability to digest lactose. The cells lining your small intestine produce the enzyme that breaks down lactose, and infections, inflammation, or injury can damage those cells. This creates a temporary intolerance that lasts days to weeks after the initial illness. Undigested lactose ferments in the colon, producing gas, cramps, and more watery stool. Yogurt with live cultures is generally better tolerated than milk because the bacteria in it help break down some of the lactose.
Insoluble Fiber
Fiber is healthy in normal circumstances, but the type matters when you have diarrhea. Insoluble fiber, the kind found in raw vegetables, whole wheat, bran, seeds, and the skins of fruits, doesn’t dissolve in water. It speeds up the movement of material through your digestive system and adds bulk. That’s helpful for constipation but counterproductive during diarrhea. Soluble fiber, found in oats, bananas, and peeled potatoes, dissolves in water and forms a gel that actually slows digestion. Choosing soluble-fiber foods over insoluble ones can help firm up loose stools.
Magnesium Supplements and Antacids
Certain forms of magnesium are well-known for loosening stools. Magnesium oxide and magnesium citrate are the most likely to cause problems. Magnesium citrate is highly water-soluble, which means it reaches the colon quickly and draws water in. In one trial using magnesium oxide at high doses, 36% of participants reported diarrhea, though reactions ranged from mild stool changes to symptoms severe enough to drop out of the study. Antacids containing magnesium hydroxide (the active ingredient in milk of magnesia) work on the same principle. If you take magnesium regularly and are dealing with diarrhea, consider pausing it or switching to magnesium gluconate or magnesium chloride, which cause diarrhea less often.
Alcohol
Alcohol irritates the gut lining, increases acid production, and disrupts the normal absorption of water and nutrients in the small intestine. It also speeds up intestinal motility, giving the colon less time to do its job. Beer and wine contain fermentable sugars that add to the problem. Even moderate drinking during a bout of diarrhea can extend it by a day or more and worsen dehydration, since alcohol itself is a diuretic.
Eating Too Little Can Backfire Too
When diarrhea hits, the instinct to eat almost nothing is understandable but can slow your recovery. The BRAT diet (bananas, rice, applesauce, toast) has been a go-to recommendation for decades, but the American Academy of Pediatrics no longer recommends it for children because it’s too restrictive and lacks the protein, calcium, and vitamins the gut needs to heal. For adults, sticking to BRAT foods for a day or two at the worst of it is fine, but returning to a normal, balanced diet as soon as you can tolerate it actually supports faster recovery. Following the BRAT diet for more than 24 hours in children may even slow down healing.
What Actually Helps
Staying hydrated is the single most important thing. If your urine is dark yellow or you’re urinating infrequently, you need more fluids. Small, frequent sips of water or an oral rehydration solution work better than drinking large amounts at once.
Certain probiotics can shorten the duration of diarrhea. One well-studied yeast-based probiotic, Saccharomyces boulardii, reduced the duration of acute diarrhea by roughly 1.5 days compared to no treatment in a meta-analysis of randomized trials. The effect was even stronger for rotavirus-related illness, cutting duration by about 2 days. Not all probiotic products contain this strain, so check the label if that’s what you’re looking for.
Beyond that, the strategy is simple: avoid the triggers above, eat bland foods with soluble fiber when you’re ready, and let your gut recover. Most episodes of acute diarrhea resolve within a few days on their own once you stop adding fuel to the fire.