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

📌 Overview and Key Takeaways

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

Discover how to meet your protein needs without causing digestive issues.

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 That Won’t Upset Your Stomach

Can Protein Powder Upset My Stomach?

Yes, protein powder can upset your stomach.

Some of the most common side effects of consuming protein powder include bloating, diarrhea, and stomach pain.

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

The cause could be the ingredients, the processing methods used to make it, or your individual food sensitivities.

Many protein powders also contain dozens of ingredients, which makes identifying the problem challenging.

That is why I wrote this article.

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

Once you learn which ingredients and processing methods to avoid, finding a protein powder that will not upset your stomach becomes much easier.

Do not forget that a registered dietitian can help you discover if underlying conditions or allergies also contribute to your upset stomach.

Why Does Protein Powder Upset My Stomach?

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

Among the most problematic ingredients are food additives, dairy-based proteins, and protein concentrates and isolates.

🚫 Avoid Food Additives

Emulsifiers, thickeners, and other ultra-processed additives look nothing like real food, which makes them hard to digest.

This can lead to a range of symptoms, from bloating to diarrhea.

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

These shifts, known as gut dysbiosis, have been linked to a number of chronic stomach issues (JGH Open, 2021).

Gut dysbiosis is so problematic because it causes a cascade of problems, including intestinal permeability and systemic inflammation.

⚠️ 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

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 a problem for everyone, can cause digestive issues too.

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.

For starters, the digestion of some caseins releases a bioactive peptide that has been linked to digestive issues (Adv Nutr, 2017).

Casein also forms a gel-like substance in your stomach that slows down digestion (Crit Rev Food Sci Nutr, 2023).

For sensitive individuals, particularly true for those with cow’s milk protein allergy or intolerance, slower digestion can contribute to bloating, constipation, and 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.

Are Some Types of Protein Powder Easier to Digest Than Others?

Some types of dietary protein are technically easier to break down and absorb than others.

One way to measure these differences is by using the Protein Digestibility Corrected Amino Acid Score (PDCAAS).

The PDCAAS takes into account both the amino acid profile of the protein and how easy it is to break down and absorb that protein.

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

Most other protein sources score considerably lower, but that does not mean that a protein powder made from them is not easy to digest.

For starters, 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 of them in the human body, 9 of which are essential, meaning you must get them from food.
• A dietary protein with sufficient amounts of all 9 essential amino acids is considered a complete protein.

Because eggs and whey are complete proteins, they have a much higher potential PDCAAS than incomplete proteins, including most plant-based proteins.

Plus, while protein powder digestibility can be scientifically measured to some degree, it is also highly individualized.

For instance, people with lactose intolerance often have a hard time digesting whey, which contains lactose, despite its high PDCAAS.

It is important to clarify that protein digestion is not impaired by lactose intolerance; the point is simply that digestion is complex.

That is, how easy a protein powder is to digest depends not only on the digestibility of the protein, but also on the presence of non-protein components.

This is why you should be concerned about how many additives and how much processing goes into making your protein powder.

Sources

1. Northern Clinics of Istanbul (North Clin Istanb). Food additives and microbiota. 2020.
2. JGH Open (JGH Open). Gut microbiota dysbiosis in functional gastrointestinal disorders: Underpinning the symptoms and pathophysiology. 2021.
3. Advances in Nutrition | Journal (Adv Nutr). Systematic Review of the Gastrointestinal Effects of A1 Compared with A2 β-Casein. 2017.
4. Critical Reviews in Food Science and Nutrition (Crit Rev Food Sci Nutr). Milk proteins: Processing, gastric coagulation, amino acid availability and muscle protein synthesis. 2023.
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.
7. 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.
8. Advances in Nutrition (Adv Nutr). Evaluation of Protein Quality in Humans and Insights on Stable Isotope Approaches to Measure Digestibility – A Review. 2022.

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.