Why Does Protein Powder Make My Stomach Hurt?

For athletes and fitness enthusiasts, consuming a protein shake before or after a workout is as important as warming up and cooling down. 

However, not all protein powders or shakes are created equal. Some can cause issues in your digestive system, like cramps, bloating, and frequent trips to the bathroom. 

This post provides evidence-based reasons why protein powder is hurting your stomach.

7 Reasons Why Protein Powder Is Causing Stomach Ache

1. You are Lactose Intolerant

One of the main reasons you are experiencing digestive issues when consuming it is that you may be lactose intolerant.

Lactose is the main carbohydrate in whey protein powder. Those lactose intolerants cannot produce enough lactase, an enzyme the body needs to digest milk well. Science shows that such a digestive disorder is common and affects up to 75% of people worldwide. 

Opt for whey protein isolate

If you’re among those with milk allergy or lactose intolerance, go for a whey protein isolate protein as it is more refined. WPIs have a significantly smaller amount of lactose and fat than whey protein concentrate. Alternatively, you can choose a non-dairy protein powder, like rice, egg, pea, hemp, or soy.

Related: Best Lactose-Free Protein Powder

2. You’re Drinking It Too Soon

Drinking protein shake too fast or too soon causes digestive issues. Most energy supports your muscles, brain, and limbs when you exercise. This slows down the digestion in your body so it can send as much blood to feed your lungs and muscles.

After completing your daily exercise routine, it still takes a while for your digestive system to function normally again. Therefore, your stomach may not be ready if you start drinking or eating immediately.

A good rule of thumb is to wait for at least 30 to 60 minutes before you drink your post-workout protein shake. Not drinking right away will give your body enough time to “settle down” and return to digest-and-rest mode, so it can effectively absorb nutrients. 

Consequently, when the body is in a rest and digest mode when you consume your protein shake, it prevents stomach pain for some.

Additionally, you may choose a protein supplement that takes less effort for your body to absorb. Some companies add digestive enzymes to their protein powder, and some increase bioavailability to make it highly digestible. So, opt for these kinds of post-workout protein powder.

3. You’re Drinking It Too Fast

I understand that you’re starving after a workout. However, consuming it too fast, like at a bar, upsets your stomach.

When you consume it too fast, you swallow more air, which causes you to gas and bloat. Drinking it too fast also promotes overeating, contributing to stomach upset and bloating.

My tip is to take a pre-workout snack before working out, so you’re not famished once you finish your workout routine. Doing so puts a stop to speed-drinking or speed-eating.

4. You are Allergic to Whey Protein 

Protein powders make it easier for active people to boost their protein intake. However, they cause stomach pain for those with allergies and digestive sensitivities.

Whey protein is derived from cow’s milk; some people have a cow’s milk allergy. It causes many symptoms, including constipation, stomach ache, and vomiting.

However, it is rare in adults. Up to 90% of individuals with cow’s milk allergies outgrow their allergy when they reach three years old. If you’re allergic to cow’s milk, opt for non-dairy protein powders like rice, hemp, pea, soy, and egg. You may also switch to natural plant protein sources.

Hemp and pea protein contains all the essential amino acids to support muscle repair and growth. People who have switched to natural protein powder sources experienced immediate relief from protein-related digestive problems.

5. You’re Sipping Artificial Sweeteners

Some protein powders contain sugar alcohols and artificial sweeteners. Your body may not absorb them very well. Once these ingredients are not entirely digested, they remain in the intestines, and the colonic bacteria will ferment them.

The by-products of such fermentation are bloating, gas, diarrhea, cramping, and gastric distress. Another reason you may be uncomfortable is that you’re also sipping inulin, a type of prebiotic that is not absorbed or digested in the stomach.

Inulin is also a non-digestible carbohydrate present in vegetables and fruits. When added to protein powders, this ingredient can cause stomach upsets.

Related: Best Protein Powder Without Artificial Sweeteners

6. You’re Using Too Much Protein Powder

When you consume too much protein, the excess is stored as fat and glycogen or excreted in the urine. 

The extra scoop can quickly turn into sugar once it hits your bloodstream. These cause nausea because of the blood sugar spike and crash.

Drinking two protein shakes daily is safe for most people. If it contains sugar and calories, it leads to weight gain and other health issues. Protein is a difficult macronutrient to digest. So, consuming too much of it can cause indigestion.

Men need to consume between 30 to 35 grams of protein. Women should aim for 20 and 25 grams of protein. It’s also good to blend your favorite nut butter, coconut oil, coconut milk, or avocado into your protein shake. Adding any of these healthy fats keeps off sugar cravings and nausea.

7. Your Body is Adjusting

You may experience stomach problems if it’s your first time taking protein supplements. It means your body takes time to adjust, and the discomfort is only temporary.

Typically, it takes about eight weeks of starting a protein powder before one can see a noticeable result in muscle definition and tone.

The Bottom line

You may experience digestive issues from consuming protein powder for the reasons we provided above. But, don’t worry. Once you know the cause, it’ll be easier for you to make the necessary changes, so you won’t be in pain after you sip.

Most importantly, choose a high-quality protein product with no added sugar if you plan to add a protein supplement to your diet. Then, get the rest of your protein needs from foods like nuts, chicken, fish, and beans.

I wish you the best of luck in your fitness journey!

For access to more fitness articles, lifestyle tips, celebrity workouts, nutrition and health info, visit ExpertFitness.org.

Nathan Lloyd, MSc

I’m a personal trainer, based in Boulder, Colorado.
I service clients physically in the Boulder area, mainly in the ONE Boulder Fitness Gym, but am also available for online consulting and coaching.

If you’re interested in my personal coaching programs, please contact me via the contact page.