This Is Why High-Protein Diets Can Mess With Your Bowel Movements Big Time
Eating a high-protein diet definitely has its pros and cons. There's no doubt that cutting back on carbs while loading up on protein has definitely helped plenty of women shed pounds. “Protein is great for anyone trying to lose weight. Since it’s digested slower than carbs, it helps you to stay full and satisfied after your meal,” says Torey Armul, R.D.
But one common downside of going high with the protein is that it can also leave you a bit, ahem, stuffed up. Yup, we're talking constipation, diarrhea, and other not-so-pleasant gastrointestinal issues. The good news is you don’t have to grin and bear it if constipation is an unpleasant side effect of your high-protein diet.
Here's what's going on below deck when your high-protein diet is making you constipated—and what to do about it.
Does eating protein normally make you poop or get constipated?
It's definitely possible to deal with either constipation or diarrhea as a result of a high-protein diet. But the issues may be indirectly related to the protein.
If you’re dealing with constipation, it might be what you're not eating that's messing with you. “It’s not the protein but a lack of fiber that causes constipation,” says Armul. “People eat less fiber on a high-protein diet since they’re more focused on eating animal proteins, which don’t have any fiber at all.”
Fiber, which is found mostly in fruits, veggies, and grains, adds bulk to your stool, drawing water and waste through your GI tract. That, in turn, helps ensure the foods you eat move more efficiently right on through. “By keeping things moving, fiber keeps you feeling good, reduces bloating, and removes any potential irritants in the GI tract,” says Armul. In short: Fiber is key.
Another thing you want to be mindful of is that protein shakes and powders can also trigger GI issues. Many of them on the market are not FDA-approved, and their ingredient lists can be unclear or misleading, warns Megan Robinson, RD, a board-certified sports dietitian. Even thought they advertise being containing no sugar or being low-carb, "a lot of them contain artificial sweeteners, stevia, and sugar alcohols, which can all be linked to stomach upset and diarrhea," Robinson says.
Robinson also says to keep in mind any intolerances or allergens you might have, especially if you consume protein powders or pre-packaged drinks. Whey protein powder, for example, contains lactose. "And if you have a lactose intolerance or dairy intolerance that can be contributing to stomach upset," Robinson says. She suggests looking for protein drinks that are certified by NSF Certified Sport or Informed Choice, two third-party companies that certify protein powders.
How do I avoid protein-related poop problems?
Your best bet is to make sure you chow down on high-fiber foods on the regular. To get the biggest bang for your nutritional buck, Armul recommends munching on plant-based proteins like lentils, chickpeas, edamame, black beans, and kidney beans. “It’s double-whammy. You’re getting protein, but you’re also reaping the benefits of fiber,” she says.
That said, if you’re going uber low-carb and generally avoiding legumes, which have more carbs than animal protein, it is still possible to stay regular by filling up on lower-carb veggies. Keep your count the lowest by choosing produce that's highly water-based, says Armul. Good options include dark leafy greens (spinach, kale, and Swiss chard are nutrient powerhouses), zucchini, cucumbers, tomatoes, squash, green peppers, and broccoli. Asparagus is an especially good pick since a cup of the stalks also have about three grams of protein, she adds.
Seeds and nuts like chia seeds, flax seeds, peanuts, almonds, and walnuts are another smart choice because they offer a heavy dose of fiber and protein with few carbs.
As for fruit, you’ve probably already heard it's good for keeping you regular. Consider adding regular servings to your diet. “I tell my clients not to worry about the natural sugars in fruits because they contain a lot of fiber that’s satiating,” says Armul. However, she says a good rule to follow for a low-carb, high-protein diet is to pick fruits with a higher ratio of skin to pulp (like blueberries). These have a lot more fiber and fewer carbs than other fruits sans skin (say, watermelon).
To keep from getting constipated, aim to eat about 25 grams of fiber per day (spread evenly over each meal). Ideally, fill half of your plate with veggies, a quarter with an animal protein (chicken, beef, fish, etc.), and a quarter with a high-protein grain or legume (like quinoa, chickpeas, or lentils). Since one cup of leafy greens has around 5 grams of fiber, a robust salad at lunch loaded with spinach, peppers, and tomatoes should get you halfway there.
Also make sure to chug more fluids. “Fiber pulls water from your body, so up water intake as you eat more of it,” says Armul. “I recommend carrying a water bottle throughout day.” Eight cups of water per day is a good place to start, but increase from there if you feel thirsty or constipated. The best indicator that you’re drinking enough is the color of your urine: If it’s light like lemonade, you’re good to go.
Are there any other side effects of too eating much protein?
Fatigued and brain fog. "Protein is not a great source of energy," Robinson says. It can be converted to sugar for energy if you go on an extremely high-protein diet, but it takes a long time to digest. "So, you're not going to get the same energy from eating a high=protein diet versus moderate protein, moderate carb," Robinson explains. And that's why the fatigue and brain fog tend to happen.
Weight gain. When you're focused on losing weight and gaining muscle mass through a high=protein diet, it can be easy to do the opposite: gain weight. How? Well, the high-protein foods Robinson typically sees her clients eating are also typically associated with fat. "And there are a lot more calories in fat than if you just had a healthy carbohydrate that has some fiber," Robinson explains.
Bad breath. This is typically more associated with someone who's on the keto diet, Robinson notes. When you send your body into ketosis, where it produces ketones (a.k.a chemicals like acetoacetate, beta-hydroxybutyrate, and acetone), it can cause bad breath.
How do I know if I'm eating too much protein?
The recommended daily allowance is 0.8 grams of protein per kilogram of bodyweight, per Robinson. "But I think if you're doing any kind of physical exercise where you're doing more than the general public, then you probably need a little bit more," Robinson says.
She suggests getting 1 gram of protein for every kilogram of bodyweight for the fairly active woman. If you want to calculate your necessary protein amount, take your weight in pounds and divide it by 2.2—that's how you get kilograms. So if you weigh 150 pounds, divide that by 2.2; that's 68 kilograms or 68 grams of protein.
If you're worried about going overboard, listen to your body. Are you becoming more irritable than normal, extremely fatigued, tired, and dehydrated? This could be a sign that you're eating too much protein and need to cut back. And, as always, you can seek out guidance from a nutritionist to help craft a nutrition plan that's right for you and your bod.
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