“Constipation is often the biggest problem with the keto diet due to the lack of fiber, but in fact, artificial sweeteners and sugar alcohols, as well as a very high fat diet, can also cause diarrhea,” says Ginger Hultin, RD, a spokesperson for the Academy of Nutrition and Dietetics and owner of Champagne Nutrition.
Keto diarrhea is exactly what it sounds like: diarrhea that happens because of the switch to the keto diet. “It could be anything from noticing looser or more frequent bowel movements to full-on diarrhea, which is generally defined as having three or more loose, liquid bowel movements in a day,” Hultin says.
But what is it about the keto diet that can cause such a crappy situation, and is there anything that can be done about it? Here’s everything you need to know about keto diarrhea.
What causes keto diarrhea?
Some people, not all, experience keto diarrhea as an unpleasant side effect when switching to the keto diet. There are a few possible reasons for keto diarrhea, Hultin says:
- Fat can be hard to digest. In general, fat takes a bit longer for the body to digest. On a high-fat diet like keto, you’re all of a sudden eating lots more avocado, nuts, seeds, meat, olive oil, and other fats than normal—which can disrupt digestion. “When you switch to this high fat of a diet, it can cause diarrhea,” says Hultin.
- Artificial sweeteners and sugar alcohols can be rough on the stomach. Additionally, like Hultin said earlier, people often eat higher amounts of sugar alcohols and other artificial sweeteners while on the keto diet. These sweeteners, while low-carb and generally considered safe, can potentially cause bloating and diarrhea when consumed in excess. So if someone is eating lots of keto-friendly products high in sugar alcohols, they might struggle with keto diarrhea.
- Keto may disrupt the gut microbiome. The keto diet can also impact the composition of your gut microbiome, which has implications for digestion, too. “There have been some small studies that have found that after three months on the ketogenic diet, the bacteria in the gut change quite a bit, and that could cause diarrhea in some people,” Hultin says. If your body is not used to eating more fats, this could alter the gut bacteria, causing diarrhea and looser stools from poor digestion. (More research needs to be done before this can be considered a conclusive issue.)
Thankfully, like keto breath, keto diarrhea is not a permanent issue. “I would expect it to occur around the time that you're changing your diet the most so in the beginning, probably the first one to four weeks until the body is able to adjust,” says Hultin.
“However, if a high-fat diet is not easy for your body to digest or if you do have changes in your gut microbiome, diarrhea could be a long-term side effect,” she says.
Beyond keto diarrhea, here's everything you need to know about the ketogenic diet:
Are there any remedies for keto diarrhea?
Again, Hultin says that keto diarrhea is usually temporary. But in the meantime, if you’re committed to keto, here are some things you can do to help stave off the worst of the runs:
- Add more fiber to your diet. “Soluble fiber is the best thing to help calm diarrhea because it absorbs water,” says Hultin. “These options are limited on a ketogenic diet but you could include: citrus, berries, avocado, broccoli, and chia seeds for example,” says Hultin.
- Drink more water and electrolytes. You can lose a lot of fluids if you have diarrhea—which is why the Mayo Clinic recommends consuming lots of liquids (water for hydration, and soups and fruit juice for electrolytes and sodium) to replenish your body.
At what point should I be concerned about this side effect?
However, if you have a stubborn case of keto diarrhea, you should consider seeing your doctor. “If you have diarrhea, especially multiple times per day, for over two to three days and if you're experiencing any symptoms of dehydration—dark colored urine, dry skin, headache, feeling dizzy or light-headed, etc.—then you should see a doctor right away,” says Hultin. You might need more serious interventions to prevent serious dehydration and to rule out other potential causes of the diarrhea.
If keto diarrhea persists, it’s worth rethinking the eating plan, says Hultin. “If the body is reacting to the high fat nature of the diet, that probably can't be changed because there's a certain ratio that must be met,” she says. No one eating plan is right for everyone, and your body might just not be cut out for high amounts of fat. Thankfully, there is a whole world of other healthy eating plans out there to discovered that don't typically involve gastric distress. Mediterranean diet, anyone?
An earlier version of this story was written by Tehrene Firman on August 28, 2018. It was updated on March 11, 2020.
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