What Are the Most Common Protein Powder Side Effects?

📌 Overview and Key Takeaways

Learn about the most common protein powder side effects,

Discover how to safely add protein powder to your diet.

Last Updated
Jan 18, 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 Side Effects

What Are the Most Common Protein Powder Side Effects?

Protein powder side effects are adverse reactions caused by the consumption of protein powder.

Some of the most common side effects of protein powder include acne, headaches, and digestive issues.

You may have read that protein powder can cause kidney damage, which is not true.

Excessive protein intake can be dangerous for individuals with impaired kidney function, but not for healthy people.

You may have also read that protein powders contain dangerous amounts of heavy metals, which is also not true.

There are detectable amounts of heavy metals in all plant-based, which does not render them unsafe to consume, nor does it discount the benefits they offer as part of a balanced diet.

To put matters into perspective, foods like rice, leafy greens, and root vegetables can contain more heavy metals per serving than protein powder.

Moreover, research shows that moderate consumption of protein powder containing heavy metals does not pose risks to human health (Int J Environ Res Public Health, 2020).

Learn more about heavy metals in protein powder.

Finally, it is worth noting that relying too heavily on protein powder as a protein source can lead to malnutrition.

It is therefore important to eat a balanced diet that includes a variety of nutrient-dense foods.

Acne

Most everyone who gets acne from protein powder uses whey or casein protein powder.

Dairy-based proteins like whey and casein can stimulate the production of insulin and insulin-like growth factor, both of which have been linked to acne development.

Although this link is not fully understood, it likely has something to do with the fact that insulin production regulates sebum production.

Sebum, an oily, waxy substance produced by your body’s sebaceous glands, can clog your pores and cause pimples.

Headaches

Here are some of the reasons why protein powder can cause headaches:

• Caffeine: Caffeine is a common headache trigger, so if you are sensitive to caffeine, you may want to avoid chocolate, coffee, and matcha-flavored protein powders.
• Sugar: Some protein powders contain lots of added sugar, which can cause spikes and crashes in blood glucose levels, leading to headaches.
• Dairy: Protein supplements made with whey or casein, can trigger a histamine response in certain individuals. This can lead to headaches, particularly in those who are histamine intolerant.
• Artificial sweeteners: For some people, the culprit may be artificial sweeteners. Although it is hard to say that there is a definitive connection between headaches and artificial sweetener consumption, a few studies have demonstrated a link (Headache, 1989).

Certain food additives can also trigger headaches and even migraines.

For this reason, sticking to a short list of simple ingredients is always the way to go.

Digestive Issues

Many protein powders are made from ingredients known to cause stomach pain 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

Regularly eating emulsifiers, thickeners, and other additives can upset your stomach because they are hard to break down.

Foods that are hard to break down feed your gut bacteria, which release gas as they eat.

And too much intestinal gas can cause bloating and stomach pain.

Regularly eating certain food additives can also alter the composition of your gut microbiome (North Clin Istanb, 2019).

Over time, this can lead to gut dysbiosis, or an imbalance in gut bacteria, which has been linked to a number of painful digestive issues (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

Note that this list includes several artificial sweeteners.

Artificial sweeteners like sucralose and acesulfame potassium are among the worst ingredients for your gut microbiome, reducing microbial diversity and promoting the growth of potentially pathogenic bacteria (Nature, 2014).

Also note that 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

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).

You 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. International Journal of Environmental Research and Public Health (Int J Environ Res Public Health). Heavy Metals in Protein Supplements: A Cause for Concern?. 2020.
2. Headache (Headache). Aspartame as a dietary trigger of headache.. 1989.
3. Northern Clinics of Istanbul (North Clin Istanb). Food additives and microbiota. 2019.
4. Microorganisms (Microorganisms). Gut Microbiota Dysbiosis: Triggers, Consequences, Diagnostic and Therapeutic Options. 2022.
5. 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.
6. Nature (Nature). Artificial sweeteners induce glucose intolerance by altering the gut microbiota.. 2014.
7. Nutrients (Nutrients). Effect of a Protein Supplement on the Gut Microbiota of Endurance Athletes: A Randomized, Controlled, Double-Blind Pilot Study. 2018.
8. 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.