Diarrhea on a high-protein diet, a side effect also called "keto diarrhea," isn't just uncomfortable. It can also lead to dehydration. The good news is that diarrhea isn't a typical side effect of a well-formulated high-protein diet, so some simple changes may be enough to solve the problem.
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In many cases, diarrhea usually isn't caused by the protein itself, but is more likely a result of the types of protein you're eating. If you're on a high-protein, low-carb diet and diarrhea develops, it doesn't mean you have to stop. It may just be a sign that you need to choose different types of foods.
Ditch the Dairy
Dairy products, like milk, cheese and yogurt are good sources of protein and they're convenient, so they're an easy choice if you're on a high-protein diet; however, in addition to containing significant amounts of protein, dairy products are also high in lactose, a natural sugar in milk. While many people have no issues with lactose, others have lactose intolerance, which results in the body being incapable of properly digesting the milk sugar.
In addition to diarrhea, lactose intolerance can cause lots of uncomfortable symptoms after you eat or drink something that has lactose in it. Other symptoms may include:
- Stomach pain
- Growling or rumbling stomach after consuming lactose
The good news is that, if you remove lactose-containing foods from your high-protein diet, diarrhea will resolve on its own, if that's the issue. Even if you're not lactose intolerant, lactose can be difficult to digest when you're having active diarrhea, according to UW Health, so it's a good idea to avoid foods with lactose temporarily.
Once your diarrhea has cleared up, you may be better able to handle foods that contain lactose, but while you're having the issue, cut them out as much as possible, whether you're lactose intolerant or not.
Look for Artificial Sweeteners
High protein diets are also usually low in carbohydrates. In some cases, people tend to replace their favorite carbohydrate-rich foods and drinks, like chocolate and soda, with processed, sugar-free options. Although these types of foods and drinks don't contain any carbohydrates and technically fit into a high-protein diet plan if you're just looking at macronutrient counts, they're not the best choices.
The sugar in sugar-free, packaged items is replaced with artificial sweeteners or sugar alcohols, two noncaloric sweeteners that aren't fully absorbed by your body. Because they aren't fully absorbed, they can cause digestive upset and lead to diarrhea. Even small amounts can cause diarrhea in people who are especially sensitive to them. While it's OK to have these types of foods as a special treat, try to avoid eating them all the time.
If you do get a sweet tooth on a high-protein diet and you're prone to diarrhea, try to stick to natural sweeteners, like stevia and monk fruit, over artificial sweeteners and sugar alcohols, like maltitol, erythritol, mannitol, xylitol and sorbitol. Better yet, try to resist the sweet tooth. The more you hold out, the easier it becomes to avoid (or at least limit) sweetened foods that might not be the best choices.
Read more: What is Sugar Alcohol and Is It Safe?
Fatty Protein and Diarrhea
In addition to naturally pushing out carbohydrates, many high-protein diets also contain a higher amount of fat than you may be used to. While prime rib and chicken thighs are good sources of protein, they also supply a pretty significant amount of fat.
According to Norton Greenberger, MD, a gastroenterologist and professor of medicine at Harvard Medical School, if you eat a lot of fat and it's not absorbed properly, the fat moves to the colon where its broken down into fatty acids that trigger the colon to secrete excess fluid. This can cause diarrhea.
In other words, although you're eating a lot of protein, diarrhea may be a product of fat malabsorption, rather than a direct result of the protein itself. If you're eating a lot of fat because you're doing keto, diarrhea may be even more likely. If you suspect this may be the problem:
- Choose lean meats, poultry and fish, like sirloin, chicken breast and wild cod, over fattier cuts, like ground beef, chicken thighs and salmon.
- Bake, broil or steam your meats and fish instead of cooking with higher-fat methods, like frying.
- Avoid creamy sauces and high-fat condiments, like sour cream, ranch dressing and mayonnaise.
Read more: Foods to Eat to Stop Diarrhea
A Word of Caution
If you're on a high-protein diet and loose stool just won't quit, it's a good idea to check with your doctor to make sure there isn't another underlying cause, like a bacterial infection or a bowel disorder, like Crohn's disease. If your health report comes back clear, there are some things you can do to help replenish lost fluid and electrolytes so you don't develop dehydration while you're working to figure out the actual culprit.
If you don't get a handle on your diarrhea, it can also cause weakness, fatigue and weight loss, in addition to dehydration. Because diarrhea is expelled so quickly and forcefully from your body, you also lose important nutrients — like calories, protein, potassium, sodium and some vitamins — with the stool, according to the Cleveland Clinic. That's why it's important to take the proper steps to get things under control as soon as possible.
The Canadian Society of Intestinal Research recommends a number of things you can do to prevent dehydration and find some relief from diarrhea while on a high-protein diet. Here's what you can try:
- Drink eight to 10 cups of fluid per day, like water, broth or weak herbal (or decaffeinated) tea.
- Eat small, frequent meals instead of a few large meals. This puts less pressure on your digestive system.
- Incorporate small amounts of soluble fiber, which can help firm up stool.
- Limit fatty, protein-rich foods, like bacon and sausage, which can worsen diarrhea.
- Temporarily reduce high-fiber foods, like raw green veggies, until diarrhea resolves.
- Drink room-temperature liquids. Beverages that are too hot or cold can promote bowel movements and worsen diarrhea.
- UW Health: "Eating Hints to Help With Diarrhea"
- Harvard Health: "Is Something in Your Diet Causing Diarrhea?"
- Canadian Society of Intestinal Research: "Diarrhea and Diet"
- Cleveland Clinic: "Nutrition Problems and Their Solutions"
- National Institute of Diabetes and Digestive and Kidney Diseases: "Symptoms & Causes of Lactose Intolerance"
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.