Protein Shakes and Bowel Movements: What to Expect

📌 Overview and Key Takeaways

This is a Dietitian’s guide to protein shakes and bowel movements.

Discover how to supplement your protein intake without causing digestive issues.

Last Updated
Jan 7, 2026

Author and Medical Reviewer

Written by Kayla Kamen, MS, RD

Kayla Kamen is a Registered Dietitian with a MS in Nutrition.

Medically reviewed by Jennifer Fossett, PA-C

Jennifer Fossett is a Physician Assistant with a BA in Nutritional Sciences.

Protein Shakes and Bowel Movements

How Do Protein Shakes Affect Bowel Movements?

Digestion begins in your mouth and ends in your bowels.

A bowel movement (pooping) is thus the last stop in your digestive tract.

Healthy bowel movements occur anywhere from three times a day and three times a week, and involve poop that is brown, soft to firm in texture, and easy to pass.

The two most common types of abnormal bowel movements are constipation and diarrhea.

Constipation occurs when poop passes through the large intestine too slowly.

Diarrhea occurs when poop passes through the large intestine too quickly.

If you experience either frequently, you should consult a licensed practitioner for personalized nutrition advice.

Protein shakes and powders are notorious for messing with digestion.

In fact, one in five people experience digestive issues when they use protein supplements, including constipation and diarrhea.

Believe it or not, the reason why protein shakes affect bowel movements typically has nothing to do with protein.

Protein shakes tend to cause constipation and diarrhea because of how much processing and how many additives were used to make them.

It follows that if you want a protein shake that will not alter your bowel movements, look for a short list of simple ingredients.

Which Protein Shakes Promote Digestive Regularity?

Not all protein supplements are created equal.

Many protein shakes and powders contain ingredients known to cause painful digestive issues and even long-term gut health problems.

Among these ingredients are food additives, dairy-based proteins, and protein concentrates and isolates.

🚫 Avoid Food Additives

Regularly eating food additives like emulsifiers, thickeners, and flavorings can not only cause diarrhea and constipation, but also alter the composition and function of your gut microbiome (North Clin Istanb, 2019).

This, in turn, can cause gut dysbiosis (Microorganisms, 2022), which contributes to a number of painful digestive issues, including irritable bowel syndrome (IBS) (JGH Open, 2021).

⚠️ Here is a list of the most common food additives in protein supplements:

• 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

As a rule of thumb, if you cannot find it in nature or make it at home, it is probably a food additive.

🚫 Avoid Dairy-Based Proteins

Dairy-based proteins like whey and casein, although not an issue for everyone, can cause digestive issues.

This is usually because they contain lactose, a sugar many individuals with sensitive stomachs cannot fully digest.

But you might be sensitive to dairy-based proteins even if you are not lactose intolerant.

This is particularly true for casein protein, which forms a gel-like substance in your stomach that slows down digestion.

🚫 Avoid Protein Concentrates and Isolates

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

Most protein supplements 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 your gut break them down.

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

Studies show that regularly eating protein concentrates and isolates might disrupt your gut microbiome (Nutrients, 2018) and cause the formation of toxic byproducts in your gut (Mol Nutr Food Res, 2024).

Individuals with pre-existing digestive issues should thus look for protein supplements made from whole food protein sources like egg whites and almonds, which are easier to digest and absorb.

Order Samples to see for yourself.

Sources

1. Northern Clinics of Istanbul (North Clin Istanb). Food additives and microbiota. 2019.
2. Microorganisms (Microorganisms). Gut Microbiota Dysbiosis: Triggers, Consequences, Diagnostic and Therapeutic Options. 2022.
3. JGH Open: An Open Access Journal of Gastroenterology and Hepatology (JGH Open). Gut microbiota dysbiosis in functional gastrointestinal disorders: Underpinning the symptoms and pathophysiology. 2021.
4. Nutrients (Nutrients). Effect of a Protein Supplement on the Gut Microbiota of Endurance Athletes: A Randomized, Controlled, Double-Blind Pilot Study. 2018.
5. 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 Registered Dietitian and reviewed by a Physician Assistant. We rely on peer-reviewed research and trusted medical sources, and regularly update our content to ensure accuracy and clarity.