How to Avoid Protein Powder Diarrhea

📌 Overview and Key Takeaways

This is a Certified Nutrition Coach’s guide on how to avoid protein powder diarrhea.

Discover what causes protein powder diarrhea so you can avoid this common side effect.

Last Updated
Jul 21, 2026

Author and Medical Reviewer

Written by Jack, CNC

Jack is a National Academy of Sports Medicine Certified Nutrition Coach.

Disclaimer: This article is for general informational purposes only and is not a substitute for personalized medical advice. Consult a licensed healthcare professional before making changes to your diet.

Protein Powder Diarrhea

Does Protein Powder Cause Diarrhea?

Yes, protein powder can cause diarrhea in some people.

In other words, if protein shakes make you run to the bathroom, you are not alone.

Having protein powder diarrhea means you have loose, watery bowel movements shortly after drinking a protein shake.

Symptoms typically last for a few hours, but some people report having diarrhea for days.

Fortunately, protein powder diarrhea is easily avoidable.

Why Does Protein Powder Cause Diarrhea?

If protein powder makes you run to the bathroom, one or more of the following ingredients is probably to blame.

🚫 Avoid Food Additives

Certain food additives can cause digestive problems.

Thickeners like guar gum are especially problematic as they can draw water into your colon, increasing the liquid content of your stool (Am J Med, 2001).

⚠️ Here is a list of the most common food additives in protein shakes and powders:

• acacia fiber
• acacia gum
• acesulfame potassium
• artificial flavors
• ascorbic acid
• aspartame
• calcium carbonate
• carrageenan
• cellulose gum
• dextrin
• dicalcium phosphate
• dipotassium phosphate
• erythritol
• gellan gum
• guar gum
• gum arabic
• inulin
• locust bean gum
• maltitol
• maltodextrin
• mono- and diglycerides
• ‘natural’ flavors
• rice bran extract
• rice dextrin
• rice hulls
• rosemary extract
• silica
• silicon dioxide
• sodium alginate
• soluble corn fiber
• sorbitol
• soy lecithin
• sucralose
• sunflower lecithin
• tocopherols
• tricalcium phosphate
• xanthan gum
• xylitol
• zinc oxide

If you could not find an ingredient in nature or make it at home, it should not be in your protein powder.

Sweeteners

Many artificial sweeteners and sugar alcohols can have a laxative effect, meaning they make you poop more often or more urgently.

This happens because these sweeteners are poorly absorbed in the intestine (Eur J Clin Nutr, 2007).

Common artificial sweeteners are sucralose and acesulfame potassium.

Common sugar alcohols are erythritol, sorbitol, and xylitol.

🚫 Avoid Dairy-Based Proteins

Dairy-based proteins like whey and casein can make you poop.

They contain lactose, which is a type of sugar found in milk.

Most adults cannot fully digest lactose (Am J Clin Nutr, 2019).

When undigested lactose reaches the colon, it pulls water into the bowel, which can cause diarrhea.

Insoluble Fiber

Insoluble fiber is a type of fiber that does not dissolve in water.

It adds bulk to the stool, so you eat a lot of it at once, it can cause diarrhea.

Most vegan protein powders naturally contain some insoluble fiber, but some contain added insoluble fiber.

This is especially true for those intended to help with weight loss.

Be careful with products like these because the added fiber is often in the form of xanthan or guar gum, which are also used as laxatives (Br J Nutr, 1993).

Preexisting Gut Issues

If any part of your digestion is not working properly, the food you eat will not be fully broken down and absorbed.

This can lead to diarrhea, among other side effects.

🚫 Avoid Protein Concentrates and Isolates

If you have a sensitive stomach, you might also want to avoid protein concentrates and isolates.

Most protein shakes and powders are made from one or both of these ultra-processed protein sources, which have been mechanically and/or chemically stripped of everything but the protein.

This includes the enzymes, fiber, and other natural digestive aids that help you break them down.

You therefore do not digest them in the same way that you do whole foods, which could affect your gut health.

For example, one study shows that regularly consuming protein concentrates and isolates might disrupt your gut microbiome (Nutrients, 2018).

Another study shows that it could cause the formation of toxic byproducts in your gut (Mol Nutr Food Res, 2024).

Although further research is needed, individuals with sensitive stomachs can play it safe by choosing protein shakes and powders made from minimally-processed protein sources like egg whites and almonds.

They are more gut-friendly.

Order Samples to see for yourself.

What Other Health Issues Could Cause Diarrhea?

Diarrhea is commonly caused by viruses like the stomach flu, bacteria, contaminated food or water sources, as well as food intolerances, medication reactions, infections, and chronic conditions.

One of the most common underlying health issues that can lead to diarrhea is lactose intolerance.

Lactose intolerance occurs when your body lacks lactase, the enzyme responsible for breaking down lactose.

Lactose is the sugar in milk and dairy products such as whey and casein.

Food sensitivities and allergies can also contribute to protein powder diarrhea.

Individuals with sensitivities or allergies to soy, for example, need to be careful when using protein powders, as some contain soy-based additives like soy lecithin.

Finally, certain digestive diseases can impact your ability to digest protein powder, leading to diarrhea.

Conditions such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD) are notorious for making people run to the bathroom.

IBS is a common disorder that affects the stomach and intestines.

IBD is a term for two conditions that cause inflammation of the digestive tract – Crohn’s disease and ulcerative colitis.

How Do I Make Protein Powder Easier to Digest?

By following these guidelines, you can minimize the risk of experiencing protein powder diarrhea:

1. Start with small portion sizes. Eating too much protein at once can overwhelm your digestive system and lead to diarrhea. Your body needs time to properly break down and absorb what you feed it. It is important to spread your protein intake throughout the day.
2. Consider timing. When you consume protein powder can also impact digestion. If you have a sensitive stomach, it might be best to consume protein powder with a meal.
3. Pair thoughtfully. Protein powder alone may not be the sole culprit behind your digestive issues. In some cases, other foods or ingredients may cause or worsen side effects like diarrhea. For example, if you are lactose intolerant and mix your protein powder with milk, you may find yourself running to the bathroom. Similarly, if you add your protein powder to a smoothie full of high fiber fruits and veggies, your digestive system might be unhappy.

In summary, while selecting the right protein powder for your digestive health is crucial, there are other factors to consider to ensure optimal digestion.

Sources

1. The American Journal of Medicine (Am J Med). Guar gum for body weight reduction: meta-analysis of randomized trials. 2001.
2. The European Journal of Clinical Nutrition (Eur J Clin Nutr). Gastrointestinal tolerance of erythritol and xylitol ingested in a liquid. 2007.
3. The American Journal of Clinical Nutrition (Am J Clin Nutr). Lactose digestion in humans: intestinal lactase appears to be constitutive whereas the colonic microbiome is adaptable. 2019
4. The British Journal of Nutrition (Br J Nutr). The effect of feeding xanthan gum on colonic function in man: correlation with in vitro determinants of bacterial breakdown. 1993.
5. Nutrients (Nutrients). Effect of a Protein Supplement on the Gut Microbiota of Endurance Athletes: A Randomized, Controlled, Double-Blind Pilot Study. 2018.
6. Molecular Nutrition & Food Research (Mol Nutr Food Res). In Vitro Fermentation of Animal and Plant Protein Isolates by the Human Gut Microbiota Under High and Low Carbohydrate Conditions. 2024.

Editorial Guidelines

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This article was written by a Certified Nutrition Coach and reviewed by a Registered Dietitian. We rely on peer-reviewed research and trusted medical sources, and regularly update our content to ensure accuracy and clarity.