Cutting down on carbs while eating more protein has helped many women lose weight. “Protein is good for anyone trying to lose weight,” says Torey Armul, a registered dietitian. “Since it takes longer to digest than carbs, it helps you feel full and satisfied after your meal.”
But there’s a downside to eating a lot of protein—it can make you constipated or cause diarrhea and other stomach problems. The good news is, you don’t have to just put up with it if constipation is bothering you.
Here’s what’s happening in your body when your high-protein diet is making you constipated—and what you can do about it.
Why would protein make you constipated?
If you’re having trouble with constipation, it might be because of what you’re not eating. “It’s not the protein but the lack of fiber that causes constipation,” says Armul. “People eat less fiber on a high-protein diet because they focus more on eating animal proteins, which don’t have any fiber.”
Fiber, mostly found in fruits, vegetables, and grains, adds bulk to your poop, helping it move smoothly through your gut. This helps your body get rid of waste more easily. “Fiber keeps you feeling good, reduces bloating, and clears any potential problems in the gut,” says Armul. In short: Fiber is important.
Another thing to watch out for is that protein shakes and powders can cause stomach problems. They’re not approved by the FDA, and their ingredient lists might not be clear. Even if they claim to have no sugar or be low-carb, many of them have artificial sweeteners and sugar substitutes, which can cause stomach issues and diarrhea, says Megan Robinson, a sports dietitian and running coach.
Robinson also says to be aware of any intolerances or allergies you might have, especially if you drink protein powders or pre-packaged drinks. For example, whey protein powder might have lactose. “If you’re lactose intolerant or sensitive to dairy, it could upset your stomach,” Robinson says. She recommends looking for protein drinks certified by NSF Certified Sport or Informed Choice, two third-party companies that certify protein powders.
How do I avoid protein-related constipation?
Your best bet is to eat high-fiber foods regularly. To get the most nutrition, Armul suggests eating plant-based proteins like lentils, chickpeas, edamame, black beans, and kidney beans. “It’s a win-win. You get protein and fiber benefits,” she says.
However, if you’re going very low-carb and avoiding legumes, which have more carbs than animal protein, you can still stay regular by eating low-carb vegetables. Choose veggies with lots of water to keep your carb count low, Armul advises. Good options include dark leafy greens (like spinach, kale, and Swiss chard), zucchini, cucumbers, tomatoes, green peppers, and broccoli. Asparagus is a great choice too, as a cup of the stalks also provides about three grams of protein, she adds.
Seeds and nuts such as chia seeds, flax seeds, peanuts, almonds, and walnuts are also a good choice because they give you fiber and protein without many carbs.
When it comes to fruit, you probably know it’s good for keeping you regular. “I advise my clients not to worry about the natural sugars in fruits because they have a lot of filling fiber,” says Armul. However, for a low-carb, high-protein diet, it’s best to choose fruits with more skin than pulp (like blueberries). These have more fiber and fewer carbs than fruits without skin (like watermelon).
To avoid constipation, aim to eat about 25 grams of fiber per day, spread out evenly over each meal. Twenty-five grams is a good minimum, says Lauren Harris-Pincus, a dietitian and author, so talk to your doctor if you’re not sure how much you need.
Here’s a meal plan that’s high in protein and fiber: Fill half of your plate with veggies, a quarter with animal protein (like chicken, beef, or fish), and a quarter with a high-protein grain or legume (like quinoa, chickpeas, or lentils). Since one cup of leafy greens has about five grams of fiber, a big salad at lunch with spinach, peppers, and tomatoes should help.
Also, make sure to drink more fluids. “Fiber takes water from your body, so drink more water as you eat more fiber,” says Armul. “Carry a water bottle with you throughout the day.” Starting with eight cups of water per day is a good idea, but drink more if you feel thirsty or constipated. The best way to know if you’re drinking enough is by looking at the color of your urine: If it’s light like lemonade, you’re drinking enough.
How much protein should I eat in a day?
“The recommended daily allowance (RDA) for protein is 0.8 grams per kilogram of body weight or about 0.4 grams per pound,” says Harris-Pincus. Following this advice, if you weigh 150 pounds, you need about 54 grams of protein every day. But, Harris-Pincus says this is more like a minimum. For best performance, it could be 1.1 to 1.4 grams of protein per kilogram, and anywhere from 1.2 to 1.7 grams per kilogram for athletes focusing on strength and endurance. (So our 150-pound person would need between 75 to 116 grams of protein.) And if you’re training to build muscle with intense workouts, you might need even more. As with most health matters, talk to your doctor if you’re unsure about what’s best for you!
No matter how much protein you eat, it’s important to have some at each meal, says Harris-Pincus. “Having at least 20 grams of protein per meal is recommended to prevent muscle loss as you get older, but ideally closer to 30 grams depending on what you need,” Harris-Pincus says. Snacking can also help you get enough protein, especially if your meals are far apart.
How do I know if I’m eating too much protein?
If you’re concerned about eating too much protein, pay attention to how your body feels and watch for signs. Are you feeling more irritable, very tired, and thirsty? This might mean you’re eating too much protein and should eat less. “Eating too much protein and too few carbs can also make you feel low on energy,” Harris-Pincus says again.
