Can Meal Replacement Shakes Cause Diarrhea?

📌 Overview and Key Takeaways

Can meal replacement shakes cause diarrhea? Discover what causes meal replacement shake diarrhea and how to avoid this common side effect.

Last Updated
Jan 11, 2026

Author and Medical Reviewer

Written by Jack, CNC

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

Meal Replacement Shake Diarrhea

Do Meal Replacements Cause Loose Stools?

Meal replacement shakes are designed to be a convenient way to replace the nutritional value of a meal.

In other words, they are a quick and easy way to incorporate calories, protein, and other nutrients into your diet.

Despite their benefits, meal replacement shakes can cause a number of unpleasant digestive issues, one of which is diarrhea.

Keep reading to learn why meal replacement shakes make people run to the bathroom.

How Do I Avoid Meal Replacement Shake Diarrhea?

Meal replacement diarrhea is easy to avoid if you are mindful of two factors: pre-existing digestive issues and ingredients.

Preexisting digestive issues can make you more likely to experience diarrhea.

When you eat, food enters your stomach where stomach acid starts to break it down into smaller components.

From there, it moves to the small intestine, where enzymes called proteases break it down into amino acids, sugars, fatty acids, etc.

These smaller components are then absorbed through the intestinal lining and enter the bloodstream, which transports them throughout the body.

If any part of this complex process is not working properly due to preexisting gut issues, the food you eat will not be fully broken down and absorbed.

This can lead to diarrhea because partially-digested food has an osmotic effect, drawing water into the colon.

So, if you think that pre-existing gut issues might be contributing to your diarrhea, consult a healthcare practitioner for a professional diagnosis.

That said, anyone can experience diarrhea if they are not careful about what they eat.

This is because some foods, especially ultra-processed ones, are hard to digest, even for healthy guts.

Here are some of the hardest meal replacement ingredients to break down and absorb:

🚫 Avoid Food Additives

Food additives like emulsifiers, thickeners, and flavors are prime examples of ultra-processed ingredients that tend to resist digestion.

Even small amounts can send you running to the bathroom.

⚠️ Here is a list of the most common food additives in meal replacements:

• 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

Regularly eating food additives can also alter the composition of your gut microbiome – the collection of microorganisms living in your gut (North Clin Istanb, 2019).

These shifts, known as gut dysbiosis, have been linked to the development of chronic digestive issues, including diarrhea (Front Microbiol, 2015).

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

🚫 Avoid Dairy-Based Proteins

Dairy-based proteins like whey and casein can cause diarrhea because they contain lactose, a sugar most adults cannot fully digest.

Avoid Artificial Sweeteners and Sugar Alcohols

Many artificial sweeteners and sugar alcohols have a laxative effect.

Common artificial sweeteners include sucralose and acesulfame potassium.

Common sugar alcohols include erythritol, sorbitol, and xylitol.

Avoid Insoluble Fiber

Some meal replacements, especially those intended to help with weight loss, contain added insoluble fiber.

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

Ingredients to look out for are guar gum and inulin.

🚫 Avoid Protein Concentrates and Isolates

Most meal replacements are made from ultra-processed protein concentrates and isolates, 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.

For this reason, they might cause digestive issues like diarrhea.

If you have a sensitive stomach, look for meal replacements make from whole food protein sources, which are easier to digest and absorb.

Order Samples to see for yourself.

What Should I Do If I Have Meal Replacement Diarrhea?

If you have diarrhea after drinking a meal replacement shake, take the following steps:

• Stay hydrated: Diarrhea can lead to dehydration due to fluid loss. Drink plenty of clear fluids and avoid caffeinated and alcoholic beverages.
• Eat bland foods: Stick to bland, easily digestible foods such as bananas and rice. These foods can help firm up stools without aggravating your stomach.
• Rest: Give your body time to recover by getting plenty of rest. Avoid strenuous activities that can further deplete your energy levels.
• Seek medical attention: If your diarrhea persists for more than a couple of days, you should consult a healthcare professional. They can help determine the underlying cause and provide appropriate treatment. Similarly, while managing meal replacement shake diarrhea at home, it is essential to monitor your symptoms closely and seek medical advice if you are unsure about the best course of action.

Keep in mind that in most cases, diarrhea only lasts 24-48 hours; if it lasts longer, consult a medical professional.

Sources

1. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Definition & Facts for Lactose Intolerance. 2018.
2. Northern Clinics of Istanbul (North Clin Istanb). Food additives and microbiota. 2019.
3. Frontiers in Microbiology (Front Microbiol). The role of gut microbiota in diarrhea and its alleviation through microbiota-targeted interventions. 2015.

Editorial Guidelines

---

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.