If Protein Powder Always Upsets Your Stomach, You Need These Pro Tips

When you eat food, your body has to break it down into smaller, usable forms that can be moved around the body. Proteins are broken down into amino acids.

Digestion begins in the mouth as you chew food into smaller pieces. From there, digestive enzymes in your saliva start to break down carbohydrates and fats. Protein digestion begins in the stomach, where pepsin is secreted to break down protein into smaller peptides. 

“The stomach produces hydrochloric acid (HCl) and pepsinogen, an inactive form of the enzyme pepsin. The acidic environment of the stomach activates pepsinogen to pepsin, which starts breaking down proteins into smaller peptides (short chains of amino acids),” explains Ashley Sauvé, CHN, a certified holistic nutritionist and herbalist specializing in digestive health.

“Adequate stomach acid is very important for protein digestion and low stomach acid can slow down protein digestion," she adds. 

Protein powder is generally digested in the same way as dietary protein. However, the absorption rate may differ depending on the type of protein powder and what it’s mixed with.

For example, whey protein is absorbed faster than casein protein. And since liquids digest faster than whole foods, a protein powder consumed without additional fat or fiber will be absorbed faster than dietary protein. 

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1.

You’re not eating enough fiber 

“Fiber has so many roles in the gut,” says Sauvé. “It improves gut motility (helps keep things moving in the gut) and feeds beneficial bacteria.” 

Consuming a high-protein diet may crowd out other macronutrients, like carbohydrates, which provide beneficial fiber, vitamins, and minerals. So it’s not what you’re eating that’s the problem (protein); it’s what you’re not eating (fiber) that can lead to constipation. 

“If less fiber is consumed to make more room for protein, then there is a higher chance of constipation, which can also lead to more gas,” notes nutritionist and gut health expert Kim Kulp, RDN.

Daily fiber needs for adults range from 21 to 38 grams, depending on age, gender, and life stage. Unfortunately, the average American only consumes1 about 17 grams of dietary fiber daily, with people following low-carbohydrate diets eating even less. 

What to do

Ensure you're getting enough fiber by eating plenty of berries, citrus, whole grains, legumes, nuts, and seeds, and supplementing with a fiber powder if needed.

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2.

It contains more fiber than you’re used to

On the flip side, plant-based protein powders like hemp protein are higher in fiber, which can affect digestion differently than animal-based protein powders that contain no fiber. 

“Since more than 95% of the American population does not consume enough dietary fiber, there is a chance that excess hemp protein powder could result in a quick jump in dietary fiber intake, which could lead to gastrointestinal issues, like bloating and gas,” Nichole Dandrea-Russert, M.S., RDN, author of The Fiber Effect previously told mindbodygreen.

For people with chronic constipation or bowel diseases, an increased fiber intake can worsen constipation2 and its associated symptoms. 

What to do

If plant proteins aggravate your stomach, try a protein powder that is lower in fiber like whey.

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3.

You’re lactose intolerant

“Protein powder can have many different sources, and if someone has a food intolerance, they might experience gastrointestinal upset when consuming protein powder derived from that food,” says Sauvé. “For example, individuals with a lactose intolerance might experience loose stools after consuming whey or casein protein.” 

It is estimated that 65 to 75% of the world’s adult population is lactose intolerant3, many of which are undiagnosed. Common signs of lactose intolerance include diarrhea, bloating, and gas. 

“Whey is a popular protein powder and does contain lactose which some people may have an issue with,” says gut health nutritionist Amanda Sauceda, MS, RDN.

While whey protein powders typically have few added ingredients, vegan protein powders could contain a blend of different plant sources and other herbs or ingredients you might not realize are causing a reaction.  

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4.

It contains artificial sweeteners 

Many protein powders contain sweeteners (low-calorie sugar substitutes) that are considered safe for consumption, but that doesn’t mean they come without side effects.

The effects of sweeteners on gut microbiota need to be further studied, however, in a review of experimental studies and clinical trials, only saccharin, sucralose, and stevia changed the composition of the gut microbiota4. 

“Some protein powders contain polyols, such as sorbitol or erythritol, to add sweetness without adding sugar,” says Kristin Draayer, MS, RDN, CPT. “These artificial sweeteners can have a laxative effect5 if consumed in large amounts, potentially leading to loose stools.” 

What to do

Switch to a protein powder that does not contain artificial sweeteners like sorbitol or erythritol.

5.

It's disrupting your gut microbiome

The gut microbiome is the collection of microorganisms that reside in your digestive tract and play a critical role in health. Protein can affect the gut microbiome6 in various ways, both positively and negatively. 

“A healthy gut includes a greater diversity of microbes,” says Kulp. “These microbes protect the lining of the intestines, improve immune function, and can reduce inflammation7 which can decrease the risk of heart disease, diabetes, and cancer.”

One study that investigated the effects of a protein supplement on the gut microbiota8 of endurance athletes found that it led to a decrease in health-promoting bacteria like Blautia, Roseburia, and Bifidobacterium longum. These bacteria are associated with improved immune function, gut barrier function, and anti-inflammatory properties. However, the long-term consequences of the decrease in these bacteria for gut health are unknown. 

In another study, dietary protein intake and exercise were associated with a higher diversity of gut microbiota in professional rugby players9. More research is needed to determine how altering gut microbiota diversity affects gut health and overall health outcomes10. 

The source of the protein can also influence the gut microbiome. Plant-based proteins likely have more effect on microbiota11 than animal proteins because of their fiber content. Some protein powders, such as whey protein isolate, contain lactoferrin and immunoglobulins that can act as prebiotics12. 

What to do

Overall, the effects of protein powder on the gut microbiome are complex and may vary depending on the type of protein powder you use, your overall diet and lifestyle, and other factors. So try a few protein powders before choosing the one that feels best to your system.

6.

You have low stomach acid

What to do

Introduce foods into your diet that help maintain an acidic stomach environment—like apple cider vinegar—if you suspect this is an issue for you.

In general, animal proteins are more easily digested than plant proteins.

However, evidence suggests14 that some plant-based proteins, like hemp, have protein digestibility scores equal to or greater than other grains, nuts, and pulses. In another study15, the protein digestion of eight protein sources was compared. Whey protein isolate and pigeon peas had the highest amino acid release. 

“Whey protein is considered a fast digesting protein16 which means that the protein can be broken down quickly and then used by the body,” explains Sauceda. “Plant-based protein powders are more likely to also have fiber that may slow down digestion, but that isn’t necessarily a bad thing. Fiber helps you stay fuller longer and your body will still get the amino acids you need.” 

Summary

Animal protein is usually easier to digest than plant protein (as long as you're not lactose intolerant). Of the plant proteins, hemp and pea are typically the easiest to digest.

1.

Experiment with different types of protein powders

There are so many different types of protein powder available on the market. If the one you’re using hurts your stomach, try another brand or protein source. 

“If you’re having ‘protein poops’ from a protein powder supplement, try switching to a different source to rule out an intolerance to the one you’re using now,” says Sauvé. “Be sure to check for sugar alcohols and other additives which could be triggering digestive issues.” 

2.

Add fiber to your protein shake

Sauvé suggests consuming protein powder alongside fiber to prevent loose stools (for example, in a smoothie with high-fiber ingredients like blackberries). “Most people overestimate the fiber content of foods, so it can be helpful to track the foods you’re eating for a few days to ensure you’re hitting your target.”

Adding fiber to protein shakes is a simple and effective way to increase dietary fiber intake and reduce the risk of digestive problems associated with protein powder consumption. 

Athletes and fitness enthusiasts might inadvertently follow dietary strategies that adversely impact the gut microbiota17.

Eating adequate dietary fiber, a variety of protein sources, healthy fats, and a wide range of vitamins and minerals has shown promising results in optimizing gut and overall health. 

“While we need protein for our muscles, cells, and immune systems, we also need plant nutrients. It’s the antioxidants and fibers that are in fruits, vegetables, whole grains, nuts, seeds and legumes that work as prebiotics, feeding our good gut microbes, so they can improve our health,” says Kulp. “The combination of protein and a variety of plant foods will give you and your microbes the food needed for a healthy gut, and healthy poops.” 

When you consume a lot of protein, excess nitrogen is flushed with fluids and water. If you aren’t drinking enough water, this could lead to mild dehydration, which can affect your bowel movements. 

Adequate hydration also helps fiber do its job properly. Fiber absorbs water as it passes through your digestive tract to soften your stools and prevent constipation. If you are increasing your fiber intake or consuming plant-based protein powders high in fiber, drinking enough water is essential.

5.

Follow serving instructions 

It’s always best practice to follow the serving instructions and directions of the supplements you are using. The proper ratio of liquid to powder could help you avoid gastrointestinal distress.

On that note, don’t dry-scoop your supplements. (Dry-scooping is a popular TikTok trend where people consume powder supplements like pre-workout or protein powder without liquid.) Along with the risk of aspiration (getting powder in your lungs), dry-scooping your protein powder can cause digestive problems.

Protein in and of itself shouldn’t cause digestive problems for most people. Certain types of protein powder or ingredients in protein powder can lead to digestive issues such as bloating, constipation, or diarrhea in some people.

To minimize these side effects, consume protein powder in moderation alongside a well-balanced diet, stay well-hydrated, and choose protein powders that don’t contain artificial sweeteners or other ingredients you might be sensitive to.