Protein Powder for Sensitive Stomachs: 10 Ingredients To Avoid

Athletic man with toned muscles doing push ups on kettlebells after taking liquid protein


Have you ever experienced stomach cramps, bloating, or other unpleasant side effects after your workout? The culprit could be your protein drink. Luckily, there are some great options when it comes to protein powder for sensitive stomachs.

Whether you have a sensitive stomach or not, the wrong ingredients (or even just too much of some ingredients) in your protein can cause an upset stomach. 

Just like with our food, we should be reading all of our supplement labels thoroughly. Not only that, but we should strive to understand how those ingredients interact with our bodies. 

To help you out along the way, we put together the 10 most common ingredients found in workout supplements that cause an upset stomach. This will help you to narrow in on the best protein powder for sensitive stomachs, so you can say goodbye to pain and bloating.  

10 ingredients to avoid in protein powder for sensitive stomachs

Let’s face it, not all workout supplements are created equal. Some are packed full of artificial ingredients, poor protein sources, and other substances that can do more harm than good. 

This list is in no particular order, and the ingredients can impact us each differently. But ideally, a protein powder for sensitive stomachs should not include these 10 ingredients: 

1. Hard-to-digest protein sources

Protein sources affect our stomachs differently, and the Dalton size of those sources influences the absorption rate. The larger the Dalton size of the protein molecules, the harder it will be for our bodies to process. 

It’s good to look for supplements with a smaller Dalton size, such as liquid protein with hydrolyzed collagen.

Many stomach sensitivities are directly related to the food that we eat, so knowing which protein powder for sensitive stomachs is easiest to digest can help you narrow things down quickly. 

While it is the most common, affordable, and accessible, be wary of whey protein isolate. It is highly processed and is often made from GMO-fed, antibiotic-ridden, and ultra-pasteurized milk. 

During the production process, whey is also stripped of alkalizing materials, vitamins, and lipids. The removal of these nutrients can over-acidify your body with frequent use, forcing calcium to be taken from your bones and leading to degenerative diseases.

It’s also important to factor in that many people are lactose intolerant, even if they don’t know it. In that case, it is best to look at a dairy-free protein option, and choose a plant-based protein or collagen protein vs whey protein.  

In most cases, plant-based proteins will be easier for our bodies - and stomachs - to process. However, this is not always the case. Many athletes struggle with pea protein due to bloating.

Additionally, it is worth noting that the majority of soy produced for food is GMO and will be sprayed with plenty of herbicides and pesticides. To avoid this, make sure to look for organic ingredients.

It may take some trial and error to narrow down the best protein powder for sensitive stomachs. When looking at the type of protein, try to find out the Dalton size and overall bioavailability. 

2. Artificial flavorings

We should steer clear of both “artificial” flavorings in our workout supplements. 

Artificial flavoring is what it sounds like – chemical-based flavors developed in a lab. Unknown chemical manipulation added to our supplements can have adverse effects on our bodies.

Unfortunately, natural flavoring isn’t always that different. While the flavors are derived from natural materials like plants and animals, flavor supplements, additives, preservatives, solvents, and emulsifiers might be added to the recipe. 

These additional ingredients in the natural flavors are not required to be listed on the ingredient list, even though they can sometimes make up around 80% of the “natural flavor.” 

The more we consume unnatural ingredients, the harder it is on our stomachs. So make sure that you are buying from a trusted company when looking for protein powder for sensitive stomachs. 

3. Excessive sweeteners

We’ve all had the unpleasant experience of drinking a sugary beverage and later feeling the wrath of “gut rot.” When we consume something with excess sugar, stevia, erythritol, fructose, or other sweeteners, a wide array of body reactions can occur. 

Sugar alcohols, like erythritol, and other sweeteners can deteriorate healthy gut bacteria. Although it may not happen the instant you consume your sweetened workout supplement, over time, these sweeteners and refined sugars can cause stomach sensitivity. 

The top collagen supplements (and other protein powders for sensitive stomachs) don’t contain any excess sweeteners. 

4. Artificial ingredients

When it comes to health, especially for active people, we should be sticking to whole foods as much as possible. Therefore, we should be avoiding all artificial ingredients, not just artificial flavoring.

When searching for a protein powder for sensitive stomachs, check to see if the vitamins in it come from a natural source. Artificial ingredients can sneakily include artificially produced vitamins and minerals. 

When you consume these artificial ingredients, most of the time, your body doesn’t know what to do with them or how to process them. This can add unnecessary stress to your digestive system, giving you an upset stomach. 

5. High levels of caffeine

Although caffeine is touted as a benefit for athletes, too much caffeine can hurt our stomachs. It’s important to find the right balance.

Caffeine can stimulate the gastrointestinal tract, leading to an upset stomach, nausea, and sometimes diarrhea. It also can increase the amount of acid in your stomach, influencing reactions like acid reflux and stomach ulcers. 

The best protein powder for sensitive stomachs is one with low (or no) caffeine content. 

6. Too much fiber

Most people that eat an average, western diet will likely fall short on fiber. However, if you have a high-fiber diet already, and then add in workout supplements fortified with fiber, you may experience abdominal bloating, stomach pain, or constipation. 

An average person, depending on their age, sex, and weight, is generally safe to consume anywhere from 25-38g of fiber per day. Some people will be okay outside that range, while others may even experience stomach discomfort within that range. 

High levels of fiber can be challenging for your body to absorb and process. Essentially, when your body has too much fiber in the digestive tract, you’re unable to pass it through your stool in the normal amount of time. This back-up is what can cause stomach pain. 

7. Sodium bicarbonate

Commonly known as baking soda, sodium bicarbonate is a common supplement for preventing and curbing muscle fatigue during and after workouts. Additionally, small, targeted amounts of baking soda can help ease acid imbalances that cause upset stomachs, like acid reflux. 

Unfortunately, as with most ingredients on our list, having too much of it can cause stomach upset. This happens because it can influence our stomach acid levels.

Usually, if taken in moderation, sodium bicarbonate will not have much of an adverse effect. However, if you are looking for protein powder for sensitive stomachs, it may be best to talk to a medical professional to see what an appropriate dosage of baking soda would be. 

8. Magnesium

Magnesium is commonly added to workout supplements due to its ability to move blood sugar into our muscles. This helps our body to dispose of lactates that build up during exercise.

Sticking to a recommended daily dose of magnesium (less than 350 mg varying with age, sex, and weight), may not bother your stomach. However, when taking more than the recommended daily dose, you may experience stomach upset, cramping, and nausea. 

9. Creatine

Creatine is often found in workout supplements as it is thought to help with muscle recovery and provide bursts of energy during high-intensity workouts. You will commonly find creatine as a stand-alone supplement, but it can be included in other pre-workout powders and liquid protein supplements. 

Creatine can cause stomach cramping, diarrhea, and nausea because it is not easily water-soluble. If you don’t drink enough water, creatine will get stuck in your gastrointestinal tract until there is enough liquid to dissolve it. 

10. High FODMAP ingredients

Anyone following a low FODMAP diet will need to be very selective with their protein powder choice. A low FODMAP diet is a common choice for people who live with irritable bowel syndrome. 

When you break it down simply, FODMAPs are certain carbohydrates found in wheat and beans. Most of the ingredients listed above would be considered high FODMAP (sweeteners, artificial ingredients, magnesium, and lactose). 

Spirulina and collagen are both excellent sources of protein for a low FODMAP diet. You can also choose from other sources for protein powder, but it is best to look for the least processed options first. 

You should select a low FODMAP workout supplement with tested ingredients, minimal added minerals, and no known additives or gut irritants (caffeine).

The best protein powder for sensitive stomachs 

The best way to find a protein powder for sensitive stomachs is by always looking at the ingredients. You should be looking for the bioavailability, protein type, processing, and any added ingredients. 

There are tons of factors that will vary from person to person when it comes to the “perfect” protein powder for a sensitive stomach. However, there is plenty of overlap in ingredients to avoid and include. 

Although protein powder is most widely used, the best supplement for sensitive stomachs may actually be a liquid protein supplement. Liquid protein shots are an effective and easy-to-absorb alternative to powder that does away with all the cons of protein powder

With liquid protein, you don’t have to mix your supplement with anything, can take the pre-packaged shots on the go in your gym bag, and can receive a very precise dosage, unlike with a powder that clumps in your blender. 

Nano-hydrolyzed collagen protein supplements like Frog Fuel are among the most effective protein supplements on the market today. This is because they are designed to have a significantly smaller Dalton size and contain high-quality digestive enzymes. 

Frog Fuel hydrolyzed collagen protein is free of GMOs and artificial flavors, and fortified with 22 amino acids, making it one of the few complete protein supplements. These easy-to-digest liquid protein shots can help you get rid of your stomach pain so you can keep your mind on your workouts. 

FAQs about protein powder for sensitive stomachs 

Here are some answers to commonly asked questions about protein powder for sensitive stomachs:

Which protein powder is easiest on stomachs?

The best protein powder for sensitive stomachs is a nano-hydrolyzed collagen protein with no irritating additives. For example, Frog Fuel collagen protein is proven to have full digestion in 15 minutes or less and contains no excess sweeteners or artificial ingredients. 

Why is my protein powder upsetting my stomach?

Protein powders can upset the stomach due to various reasons, such as lactose intolerance (in whey protein), sensitivity to certain ingredients, or consuming too much protein at once. 

It is very common to have a “too much protein stomach ache,” but it could also be due to added ingredients like artificial sweeteners or preservatives.

Is whey protein good for sensitive stomachs?

Whey protein can be challenging as a protein powder for sensitive stomachs due to its lactose content and digestion rate. You may have better luck with collagen protein or a plant-based protein like pea or hemp. 

How to stop stomach pain from whey protein?

If you are experiencing stomach pain after using whey protein, you may just need to ride it out. You can try taking a lactose pill to see if it curbs indigestion, but realistically you should switch to a dairy-free and easy-to-digest protein option like hydrolyzed collagen protein. 

Best Sellers

Knowledge & Resource

The Science of FrogFuel

See what makes Frogfuel stand out
from the rest of the pack.
See the Science
Knowledge & Resource

Advanced Training Tips

Take your training to the next level
View More Blogs