Protein Powder for Sensitive Stomachs: 10 Workout Supplement 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 powder or liquid 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.  

10 ingredients to avoid if you have a sensitive stomach

Let’s face it, not all workout supplements are created equal. Some are packed full of artificial ingredients, non-ideal 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

Different types of 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. So, 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 proteins are best for sensitive stomachs 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.

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 for you. When looking at the type of protein, try to find out the dalton size and overall bioavailability. 

2. Flavoring

We should steer clear of both “artificial” and “natural” 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 that different. While the flavors are derived from natural materials like plants and animals, flavor supplements, additives, preservatives, solvents, and emulsifiers need to 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. 

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. 

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 we consume these artificial ingredients, most of the time, our body doesn’t know what to do with it or how to process it. This can add unnecessary stress to our digestive system, giving us 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. 

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, especially when consumed in a short period, 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 already have a sensitive stomach, it may be best to talk to a medical professional to see what an appropriate dosage 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. Any high FODMAP foods

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 that 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 powders and options 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, liquid protein supplements are an effective and easy to absorb alternative. 

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 shots are free of GMOs and artificial flavors, and fortified with 22 amino acids, making them 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. 

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