4 Reasons Drinking Soda May Cause Diarrhea

Does drinking soda upset your stomach and cause diarrhea? If so, you're not alone, says William J. Bulsiewicz, MD, a gastroenterologist with Lowcountry Gastroenterology in Mount Pleasant, South Carolina, and author of the forthcoming book ​Fiber Fueled​. And there are various reasons for this.

For starters, there's the caffeine factor, says Dr. Bulsiewicz. "A handful of people with irritable bowel syndrome (IBS) will have an aggravation of their IBS when they consume caffeine," he says. "They don't tolerate caffeine well, and it will give them diarrhea." A common gastrointestinal disorder, IBS symptoms include constipation, diarrhea and abdominal pain and bloating, according to the American College of Gastroenterology.

Caffeine may stimulate the intestines and increase motility, Dr. Bulsiewicz says. Motility refers to the movement that causes stool to travel through the digestive tract for elimination, he explains.

Aside from caffeine, the amount of sugar in soda may also cause diarrhea. "If you overwhelm your body with sugar, you will get diarrhea," Dr. Bulsiewicz says. Sugar-sweetened sodas are the top source of added sugar in our diets, the American Heart Association points out.

Some sugary sodas also contain high-fructose corn syrup, which is a combination of fructose and dextrose, according to the Mayo Clinic. You may have trouble digesting fructose. This condition is called fructose malabsorption, and symptoms include bloating, stomach pain, heartburn, diarrhea and gas.

Sugar comes in different forms with different names, says Mayo Clinic. To avoid it, read product labels carefully and avoid soda with:

• Fructose
• High-fructose corn syrup
• Honey
• Agave syrup
• Invert sugar
• Maple-flavored syrup
• Molasses
• Palm or coconut sugar
• Sorghum

​Read more:​ The Top 10 Worst Soft Drinks for Your Health

Dr. Bulsiewicz cautions that "if you opt for diet soda, artificial sweeteners may be worse." Artificial sweeteners can have a laxative effect. "They pull water into the colon and help to mobilize the stool, which can cause the runs," he explains.

Another reason that soda may cause diarrhea is the carbonation that gives soda its fizz. This can create belching, flatulence and indigestion. "It won't cause irritable bowel syndrome (IBS), but if you are someone who is sensitive to carbonated beverages and you have IBS, the bloating and gas may case a flare and lead to diarrhea," Dr. Bulsiewicz points out.

It makes sense to avoid or limit the amount of soda you drink for many reasons, especially if it upsets your stomach and leads to diarrhea.

A review 30 of studies published in December 2017 in the journal ​Obesity Facts​ showed that regularly drinking sugar-sweetened beverages leads to obesity in children and adults. Fully 93 percent of the studies in the review found an association between the onset of overweight or obesity and drinking sugary beverages in children and adults.

Substituting no- or low-calorie drinks such as water and low-fat or fat-free milk for sugary sodas can help aid weight-loss efforts, according to the Centers for Disease Control and Prevention. These are also better choices to ensure good hydration. The Academy of Nutrition and Dietetics recommends that women aim for about 11 1/2 cups of water each day and men aim for about 15 1/2 cups. These recomendations include water from both beverages and foods.

"If soda gives you diarrhea, ginger ale may be a better choice," Dr. Bulsiewicz says. "If you get real ginger ale, it contains ginger, which has medicinal properties that can calm an upset stomach, and it is caffeine-free."

Though unpleasant, diarrhea from soda is probably not dangerous, but "if you have a change in bowel habits, see blood in your stool and are experiencing weakness, fatigue and unexplained weight loss, or if these symptoms are chronical and escalating, see your doctor," he adds.

​Read more:​ Are There Health Benefits of Soda and Carbonated Water?