How to Find a Protein Powder That Won’t Upset Your Stomach

📌 Overview and Key Takeaways

This is a Dietitian’s guide on how to find a protein powder that won’t upset your stomach.

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

Last Updated
Jan 8, 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 Powder That Won’t Upset Your Stomach

Can Protein Powder Upset My Stomach?

If protein powers upset your stomach, you are not alone! The most common side effect of consuming protein powder is digestive issues like bloating, diarrhea, and stomach pain.

Exactly why a particular protein powder upsets your stomach is complicated.

It could due to the ingredients, the processing used to make it, or even individual food sensitivities.

Moreover, there are so many ingredients in the average protein powder that identifying the problem can be challenging and expensive, which is why I wrote this article.

Below is a summary of the top reasons why protein powder can cause digestive issues.

Once you figure out what types of ingredients and processing to avoid, you will have a much easier time finding a protein powder that won’t upset your stomach.

Note that consulting with a registered dietitian is a great way to discover if underlying conditions or allergies are contributing to your upset stomach.

Now, without further ado, here is everything you need to know about protein powder and digestion.

Why Does Protein Powder Upset My Stomach?

Many protein powders are made with ingredients that can cause painful digestive issues and long term gut health problems. Among these ingredients are food additives, dairy-based proteins, and protein concentrates and isolates.

🚫 Avoid Food Additives

Emulsifiers, thickeners, and other additives are so processed they are hard to digest. It follows that they feed your gut bacteria, which release gas as they eat.

Too much intestinal gas can cause bloating, flatulence, stomach pain, and even constipation.

Partially digested food additives can also cause your colon to absorb too much water, leading to diarrhea.

Moreover, regularly eating food additives can alter the composition of your gut microbiome (North Clin Istanb, 2019).

This can lead to gut dysbiosis, or an imbalance in gut bacteria, which is linked to the development of chronic digestive issues like irritable bowel syndrome (IBS) (Microorganisms, 2022; 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 and cause the formation of toxic byproducts in your gut (Nutrients, 2018; 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.

Are Some Types of Protein Powder Easier to Digest Than Others

In case you were wondering, some types of dietary protein are easier to digest than others.

The most widely accepted way to measure these differences is by using the Protein Digestibility Corrected Amino Acid Score (PDCAAS), which takes into account both the amino acid profile of the protein and how easy it is to break down and absorb that protein (Br J Nutr, 2012).

Protein sources like eggs and dairy have a PDCAAS of 1.0, which is the highest possible score.

Most other protein sources score considerably lower, but that does not necessarily mean they are harder to digest.

For one thing, the PDCAAS is biased towards a dietary protein’s amino acid profile.

As a reminder:

• Amino acids are the building blocks of protein.
• There are 20 amino acids in the human body, 9 of which are essential, meaning we must get them from food.
• A dietary protein with all 9 essential amino acids is considered a complete protein.

Because eggs and dairy are complete proteins, they have a much higher potential PDCAAS than incomplete proteins like peas.

Given this inherent bias, some people choose to focus on ileal digestibility, which is a measurement of how well nutrients are absorbed by the small intestine, specifically at the end part known as the ileum (Adv Nutr, 2021).

Animal-based protein sources like eggs and dairy tend to have higher ileal digestibilities than plant-based protein sources like peas, which further reinforces the idea that they are easier to digest.

But here is where things get complicated. Digestion involves the entire digestive tract, which is made up of organs, microorganisms, enzymes, acids, and other compounds that work together to help you break down the food you eat.

And the function and composition of the digestive tract can vary significantly from person to person – lactose intolerance is a good example of this – so foods that are easy to digest for one person may be hard to digest for someone else.

It follows that protein digestion outside of a controlled laboratory environment is super complicated. Worrying about it is thus not worth your time and energy.

Instead, what you should be concerned about is how much processing and how many additives were used to make your protein powder.

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.
6. The British journal of nutrition (Br J Nutr). Advantages and limitations of the protein digestibility-corrected amino acid score (PDCAAS) as a method for evaluating protein quality in human diets. 2012.
7. Advances in Nutrition (Adv Nutr). Evaluation of Protein Quality in Humans and Insights on Stable Isotope Approaches to Measure Digestibility – A Review. 2021.

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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.