Do Protein Shakes Cause Constipation? (Causes & How To Fix)

Many of my clients take protein to help them reach their protein goals, but some find it also causes constipation. I’ll teach you how I helped them fix their constipation so that they could increase their protein intake without digestive distress.

Do protein shakes cause constipation? Protein shakes can cause constipation if you have food sensitivities to either sugar alcohols or fiber. To decrease your symptoms, it’s important to avoid these triggers and consume a variety of whole foods alongside your protein shakes or use a higher-quality protein powder without these ingredients.

Below I’ll help you figure out whether your digestive issues are caused by the ingredients in your protein powder, the amount you’re consuming, or the lack of nutrition in your overall diet.

After reading this article, you’ll learn:

  • If protein shakes can affect your digestion
  • Why protein shakes could be causing you to become constipated
  • How to find and eliminate triggers of your constipation
  • What to look for in a protein powder if they normally make you constipated

Do Protein Shakes Affect Your Poop? 

Protein shakes can affect your poop if you’re sensitive to the protein powder that you’re using or overconsuming it. Although it’s common for protein shakes to affect digestion, it’s certainly not normal. 

It’s important to pinpoint the underlying issue so that you can increase your protein intake without experiencing digestive issues like diarrhea, constipation, and bloating.

The questions that you should ask yourself to start are:

  • Do you have any known food sensitivities? 
  • Have you changed anything else in your diet since incorporating protein powder? 
  • Are there other foods besides protein powder that make you feel similarly?
  • Can you tolerate the liquid that you’re using to mix your protein powder by itself?

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4 Reasons Whey Protein Shakes Can Cause Constipation

4 reasons whey protein shakes can cause constipation 

The 4 reasons whey protein could cause you to be constipated are:

  • You’re lactose intolerant
  • You’re sensitive to sugar alcohols
  • Your protein powder is too low or too high in fiber
  • You’re consuming more protein shakes than whole food

1. You’re Lactose Intolerant

The main reason why people often become constipated when consuming protein shakes regularly is that they’re lactose intolerant or sensitive to dairy and just don’t know it. 

If you don’t normally consume many dairy products and suddenly you’re introducing regular shakes made with whey protein, then it’s likely that you’re dealing with a food sensitivity to lactose or dairy in general.

Different people have different issues with dairy products: some are only sensitive to lactose and can consume lactose-free products, and some are sensitive to dairy products in general because of the whey and casein that they contain.

How To Fix It

First, I would try switching to a lactose-free protein powder and seeing if this alleviates your symptoms of constipation. If symptoms subside, then we can conclude that you are lactose intolerant, which was the cause of your digestive issues.

If symptoms do not subside after switching to a lactose-free protein powder, then lactose was not the problem, and it could be a dairy intolerance or allergy instead. Try switching to a dairy-free protein powder to see if your symptoms subside.

At this point, if you’re still experiencing constipation with your protein shakes, then we can rule out lactose and dairy as the culprits and move on to another potential trigger.

Pro tip: When you’re in the process of figuring out what your triggers are, it’s best to look for protein samples rather than purchasing an entire tub because if you were to buy a tub of lactose-free protein, but it still didn’t alleviate your symptoms, then you’d be stuck with a protein powder that still doesn’t work for you.

To get a free sample of a protein powder that you’re interested in, you can head to a local supplement store or email the company directly. 

Most supplements stores have free samples of their protein powders, but if they don’t have the specific one that you’re looking for, then you can email the company directly and explain that you want to try a sample before purchasing because of your sensitivity to other protein powders. Some companies might give you a sample for free. 

Other companies, lke Revolution Nutrition, will allow you to buy sample packs of protein for $10.  

2. You’re Sensitive To Sugar Alcohols

Another possible cause of your constipation when consuming protein shakes could be a sensitivity to sugar alcohols. Sugar alcohols have been known to cause digestive issues in many individuals, and they’re often used in protein powders to cut calories while maintaining sweetness.

Check the ingredients list on your protein powder and look for sugar alcohols like mannitol, sorbitol, xylitol, lactitol, isomalt, maltitol, and hydrogenated starch hydrolysates (HSH). 

How To Fix It

If your protein powder contains one or more sugar alcohols and you’re experiencing constipation when consuming it, then the best thing for you to do is switch to a protein powder that doesn’t contain sugar alcohols and see how you feel.

Look for a protein powder that is sweetened with stevia or sugar and is free of sugar alcohols and other artificial sweeteners. My favorite protein powder made without sugar alcohols and artificial sweeteners is Naked Nutrition’s Naked Protein.

If you notice that with taking this new protein powder, your symptoms subside, then it’s fair to say that sugar alcohols, or artificial sweeteners in general, were a trigger for you.

However, if your symptoms don’t subside, then something else in your protein powder is causing your constipation issues. 

3. Your Protein Powder Is Too Low Or Too High In Fiber

Other possible causes of your constipation when drinking protein shakes is a lack of fiber or a fiber overload. 

A lack of fiber can cause constipation by affecting the consistency of your stool, making it too hard to pass. However, a fiber overload can also cause constipation, bloating, and gas by adding too much bulk to your stool, making it difficult to pass.

Most advice on the internet says that you should choose a high-fiber protein powder if you’re experiencing constipation, but this isn’t always great advice because if someone is already overconsuming fiber and adds more, they will become severely constipated.

People often forget that there are 2 different types of fiber: soluble and insoluble. Soluble fiber adds bulk to your stool, while insoluble fiber helps things pass through your digestive system more easily.

The type of fiber in protein powder is primarily soluble fiber, so choosing a higher-fiber protein powder when you’re already constipated may not be the best course of action because it would only add more bulk without improving its ability to pass.

How To Fix It

The two ways to fix this are to try a lower-fiber protein powder with 5g or less fiber per serving and to drink more water. My favorite low-fiber protein powder is the KOS Organic Plant-Based Protein because it only has 2g of fiber per serving, and it also contains digestive enzymes to aid with digestion.

Consuming lower amounts of fiber from your protein powder when you’re already getting enough throughout the rest of the day (~25g per day for women ~38g for men) will take some strain off your digestive system and encourage better digestion.

If you suspect you aren’t getting enough fiber throughout the day (mostly insoluble) and this is what’s contributing to your constipation, then I recommend adding whole-wheat products, wheat bran, nuts, beans, cauliflower, green beans, and potatoes to your diet to help things pass more smoothly.

Additionally, increasing your water intake can help soften your stool and allow things to pass more smoothly because things can get backed up without enough water to help flush out your digestive system.

4. You’re Consuming More Protein Shakes Than Whole Foods

Lastly, you could be experiencing constipation with your protein powder because you’re not getting enough vitamins and minerals from whole foods to facilitate healthy digestion. 

If you have protein shakes more often than you have whole food sources of protein, fruits, and vegetables, then it can cause issues.

How To Fix It

Increase your consumption of whole foods by limiting yourself to one protein shake per day to allow for other whole food sources of protein throughout the day. 

If you need more than one protein shake a day because you have a higher than normal protein requirement, then be more intentional about adding more fruit and veggies to your protein shakes to increase the number of nutrients that you’re consuming.

Considerations For A Whey Protein That Doesn’t Cause Constipation

The top considerations for choosing a protein powder that doesn’t cause constipation are:

  • Choose a lactose-free and/or dairy-free protein powder
  • Avoid protein powders with sugar alcohols
  • Pick one that has an appropriate amount of fiber for you

Choose A Lactose-Free and/or Dairy-Free Protein Powder

Dairy products are the number one trigger for those with digestive issues related to protein powder, so if you’re struggling with constipation, these ingredients should be the first to go.

Luckily, many plant-based proteins exist that are excellent options for those who want to increase their protein intake while avoiding lactose or dairy altogether. 

My favorite dairy-free protein is the same as my favorite low-fiber protein, the KOS Organic Plant-Based Protein, because it also contains digestive enzymes that help your body break it down more easily during digestion, and it tastes amazing – which is saying something considering most plant-based protein powders taste disgusting.

Avoid Protein Powders With Sugar Alcohols

Another consideration is to shop for a protein powder that is sweetened with stevia or sugar rather than sugar alcohols. 

To find a suitable product, it’s important to read the ingredients list rather than the nutrition label because the label might say the product has 0 grams of sugar alcohol even if they are in the product.

The FDA allows companies to claim 0g on the label if the product has less than 1g of that particular ingredient. However, the ingredient list always has to list every ingredient, so it’s a better reference point than the nutrition label itself.

Most protein powders that are free of artificial sweeteners will be advertising this because it’s a selling factor for them, so look for brands that are free of artificial sweeteners and that are third-party tested, like Naked Nutrition’s Naked Protein

Products that are third-party tested have been verified for label accuracy, so if it’s claiming to be free of artificial sweeteners and it’s third-party tested, then the chances of that being true are much higher.

Pick A Protein Powder That Has An Appropriate Amount Of Fiber

The last consideration is picking a protein powder with an appropriate amount of fiber based on how much fiber you consume from whole food sources.

If you’re achieving around 25 grams (women) or 38 grams (men) per day, then choose a protein powder with less than 5 grams of fiber per serving to encourage better digestion rather than constipating you further.

If you’re not even close to this daily fiber intake, then it may be better to go for a higher-fiber protein powder like Manitoba Harvest’s Hemp Yeah! Protein, to add more bulk to your stool.

Other Side Effects of Protein Powder

Frequently Asked Questions

How Common Is It For People To Get Constipation After Drinking Whey Protein?

It’s common for people to get constipated after drinking whey protein because there are multiple ingredients in protein powders that people can be sensitive to; in fact, nearly 40% of people who consume whey protein powder experience either constipation.

If I Have Constipation After Drinking Whey Protein Does The Protein Go To Waste? 

Your body can likely still break down the protein component of the protein powder, meaning that the amino acids from the protein are still being absorbed and can function appropriately; however, it will come at a cost of digestive distress, which means it’s not worth continuing to use that protein powder.

Can Drinking Too Much Protein At Once Cause Constipation?

Yes, especially if it contains ingredients that you’re intolerant to and/or you’re not consuming enough whole foods throughout the rest of the day to provide you with an adequate amount of fiber, vitamins, and minerals that your body needs to function optimally.


Parker, A.M., & Watson, R.R. (2017). Chapter 16 – Lactose Intolerance. In R.R. Watson, R.J. Collier, & V.R. Preedy (Eds.), Nutrients in Dairy and their Implications on Health and Disease (pp. 205-211). Academic Press. ISBN 9780128097625.

Grembecka, M. Sugar alcohols—their role in the modern world of sweeteners: a review. Eur Food Res Technol 241, 1–14 (2015).

Ho, K. S., Tan, C. Y., Mohd Daud, M. A., & Seow-Choen, F. (2012). Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms. World journal of gastroenterology, 18(33), 4593–4596.

About The Author

Amanda Parker

Amanda Parker is an author, nutrition coach, and Certified Naturopath.  She works with bodybuilders, Olympic weightlifters, and powerlifters to increase performance through nutrition and lifestyle coaching.

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