Upping Your Protein Intake? Here’s Exactly How It Can Affect Your Poop

If you've ever found yourself sprinting to the bathroom post-protein shake, you're not alone. You might even be wondering if your go-to protein supplement is to blame. While protein is essential for building and repairing muscle, it can also have some unexpected effects on your gut. So it begs the question, does protein make you poop?

We tapped two gastroenterologists and a registered dietitian to break down what's really going on in your gut after a scoop of protein, including which ingredients could send you running to the bathroom and what to do if your post-workout routine gets a little too regular (if you know what we mean).

Do protein products cause bowel movements? 

First things first…it's important to note that *anything* you eat could trigger a bowel movement. "Ultimately, any kind of food can trigger digestion and potentially stimulate a bowel movement, including protein in any form—such as shakes or powders," explains Marlee Hamilton, a registered dietitian with Ignite Nutrition in Canada.

Why exactly does this happen, you ask? It's due to something called the "gastrocolic reflex," which Hamilton explains is a natural response where eating or drinking something with calories stimulates movement in the colon, sometimes prompting a bowel movement soon after.¹

But what about things like protein bars and shakes? Hamilton notes that while protein itself isn't usually the direct cause of bowel movements, certain ingredients in commercial protein products may be more likely to trigger a bowel movement.

Take sugar alcohols, for example.² Hamilton explains that sugar alcohols like sorbitol have been shown to pull water into the colon and speed up gut motility (aka the movement of waste through the gut), and may trigger an upset stomach, especially in people who live with digestive conditions such as irritable bowel syndrome (IBS).

Similarly, some protein products have added fiber, especially in the form of inulin or chicory root.^3,4 "While fiber is critical for digestion, these particular types may increase bowel activity, especially if you're not used to eating them," Hamilton explains.

Some thickeners or gums (like xanthan and guar gum) may also disrupt digestion in sensitive individuals, which can lead to changes in your bowel movements, according to Sarah Robbins, a gastroenterologist based in Calgary, Canada.

In addition, certain health conditions can make you more likely to react to the ingredients in protein products, says Eric Yoon, MD, a gastroenterologist at Manhattan Gastroenterology. According to Dr. Yoon, the following conditions may increase sensitivity to protein products:

• Lactose intolerance: Eating products containing whey protein concentrate (which contains lactose, a sugar found in milk) can promote gas, bloating, abdominal cramps, and diarrhea in people with lactose intolerance. The solution? Choose whey protein isolate. According to Hamilton, whey protein isolate goes through additional processing to remove most of the lactose, which makes it more tolerable for people with lactose intolerance.
• IBS: Sugar alcohols, inulin, chicory root, or soy in some protein products can trigger IBS symptoms, as these ingredients are high in FODMAPs (fermentable carbohydrates that can trigger gas, bloating, abdominal pain, and diarrhea in sensitive individuals).
• Celiac disease: Protein products with gluten-containing additives like wheat or barley, or cross-contamination during the manufacturing process, can trigger gut symptoms in people with celiac disease or gluten sensitivity.
• Histamine intolerance: Nausea, diarrhea, flushing, and headaches may occur after eating aged or fermented proteins like cured meats or aged cheese in people who are sensitive to histamines.
• Post-gallbladder removal or pancreatic insufficiency: High-fat foods and protein supplements could be difficult to digest for people without a gallbladder or those with pancreatic insufficiency (a condition where your pancreas doesn't produce enough digestive enzymes), leading to diarrhea, bloating, and nausea.

As you can see, it's often not the protein itself causing the digestive issues, but ingredients that could be present in protein products (like lactose, gluten, histamine, or fat) that may lead to changes in your bowel movements.

So, what about protein in foods? 

Depending on the ingredients in your protein powder or shake, there's definitely a chance they could trigger a bowel movement. But what about protein in foods? Hamilton shares that protein from whole foods can cause changes in your poop habits and overall digestive symptoms too, but this is often dependent on the food you eat and can vary from person to person.

For example, "Some people may experience gas, bloating, or discomfort after eating legumes due to their higher fiber and FODMAP content," Hamilton says. "Others may find that red meat or higher-fat cuts of meat feel heavy or are slower to digest." Ultimately, each type of protein has pros and cons, and the best choice often depends on individual goals and digestive tolerance, Hamilton explains.

What to do if protein upsets your stomach 

So you've upped your protein intake, but you're experiencing some changes in your digestive health. What gives? Well, turns out that we all respond to protein products and foods differently. Some of us may not experience any changes in our overall gut health and pooping habits at all. But according to Dr. Robbins, people with underlying health conditions like inflammatory bowel disease or lactose intolerance may be more prone to increased bowel movements after eating protein.

If you want to increase your protein intake without upsetting your stomach, our experts recommend the following strategies:

• Look for protein products with minimal ingredients: Many protein products have long ingredient lists, including sweeteners (like sugar alcohols), vegetable powders, and extra fiber, often in the form of inulin or chicory root. Instead, choose a protein powder without these ingredients to minimize discomfort.
• Choose whey isolate or plant-based options: Whey isolate is more processed, but it's not necessarily a bad thing, as it contains less lactose and is often better tolerated for people with sensitivities.
• Increase protein intake slowly: If your body isn't used to eating a lot of protein, it's important to start slowly and gradually add more as your body adjusts to the increase in intake. Try a half scoop of protein powder and see how you respond before going for the full serving.
• Consume protein with other foods: Mixing protein with fats, fiber, or complex carbohydrates can slow digestion and improve tolerance to protein.
• Stay hydrated: If you're prone to constipation, it's important to keep yourself hydrated, especially if you're eating more protein. Make sure to keep a water bottle handy and sip away throughout the day to ensure that your digestive tract is moving smoothly.

As with anything to do with nutrition, each person is different, and what works for one person may not work for another. It's all about discovering your own individual tolerance and adjusting your eating plan based on your needs and health goals. 

The bottom line 

If you've ever had to run to the bathroom after your protein shake, you're not the only one—and no, you're not imagining things. While protein itself isn't usually the direct cause, certain ingredients in protein products (like sugar alcohols, added fiber, and lactose) can definitely get your gut moving. And even whole food proteins like beans or red meat can cause changes in digestion in people with certain health conditions or food intolerances.

Protein is a key part of a healthy and balanced diet, but if your supplement is sending you straight to the bathroom, it might be time to take a closer look at the ingredient label. And if you're unable to find a protein that works for you? A dietitian can help you navigate ingredient labels and find a digestion-friendly option that fits your individual needs—no emergency bathroom trips required.