7Up is not a good treatment for diarrhea and can actually make it worse. Despite the long-standing home remedy of sipping flat lemon-lime soda when you have a stomach bug, the drink contains too much sugar, too little sodium, and no potassium to help your body recover. A 12-ounce can of 7Up has 38 grams of sugar, which is enough to pull more water into your intestines and loosen your stools further.
Why Sugar Makes Diarrhea Worse
Sugars stimulate the gut to push out water and electrolytes, which loosens bowel movements. This process, sometimes called osmotic diarrhea, happens when there’s a high concentration of sugar in the intestines that your body can’t absorb fast enough. The excess sugar draws water in rather than letting your body absorb it, which is the opposite of what you need when you’re already losing fluids.
The CDC specifically warns against foods and drinks high in simple sugars during diarrheal illness, noting that the osmotic load can worsen symptoms. Carbonated soft drinks, juice, and gelatin desserts all fall into this category. With 38 grams of sugar packed into a single can, 7Up delivers roughly five times the sugar concentration found in a properly formulated rehydration drink.
7Up Lacks the Electrolytes You’re Losing
When you have diarrhea, your body loses sodium and potassium with every trip to the bathroom. Replacing those electrolytes is the entire point of rehydration. Here’s how 7Up stacks up against a standard oral rehydration solution like Pedialyte, per fluid ounce:
- Sodium: 7Up has 3 mg. Pedialyte has 45 mg.
- Potassium: 7Up has 0 mg. Pedialyte has 20 mg.
That’s not a small gap. 7Up provides almost none of what your body actually needs to rehydrate. Effective rehydration depends on a roughly 1:1 ratio of sodium to glucose in the gut, which allows your intestines to absorb water efficiently. 7Up’s formula is essentially all sugar and almost no sodium, so it bypasses this absorption mechanism entirely.
Carbonation Adds Discomfort
The bubbles in 7Up are carbon dioxide gas, and that gas has to go somewhere once it’s in your stomach. During a bout of diarrhea, your digestive tract is already irritated and working overtime. Adding carbonation on top of that typically increases bloating and abdominal discomfort. Even letting the soda go flat doesn’t solve the underlying problems of too much sugar and too few electrolytes.
Where the “Flat Soda” Advice Came From
The idea of drinking flat soda for an upset stomach has been passed down for generations, but it was never based on solid clinical evidence. A review published in the BMJ examined this practice directly and found that carbonated drinks, whether flat or fizzy, “provide inadequate fluid and electrolyte replacement and cannot be recommended.” The researchers noted that common sodas have an osmolality of 388 to 790 mOsm per kilogram of water, far exceeding the 333 mOsm recommended by the WHO for rehydration solutions. In plain terms, these drinks are so concentrated with sugar that they work against your body’s ability to absorb fluid.
The review concluded that parents and caregivers should be discouraged from using flat fizzy drinks for rehydration purposes, particularly in children with stomach bugs.
What to Drink Instead
An oral rehydration solution is the gold standard for replacing what diarrhea takes from your body. Store-bought options like Pedialyte or similar electrolyte drinks are formulated to match the sodium-to-glucose ratio your gut needs for efficient absorption.
If you don’t have a commercial rehydration drink on hand, you can make one at home with four cups of water, half a teaspoon of table salt, and two tablespoons of sugar. This recipe, recommended by the University of Virginia School of Medicine, delivers a much better balance of sugar and sodium than any soda. You can add a flavor packet if the taste is too plain.
For mild diarrhea in adults, water and broth also work well. The goal is steady sips throughout the day rather than gulping large amounts at once. If diarrhea lasts longer than 24 hours, comes with a fever above 102°F, or includes bloody or black stools, those are signs that something more serious may be going on and professional evaluation is warranted.