Are ‘Protein Farts’ a Real Thing?

But are protein farts truly caused by protein itself? The answer is nuanced: In most cases, it’s not just protein, but the type of protein, how much you’re eating at once, and the additives that may come along with it.

Here’s a look at why high-protein diets can lead to bloating and flatulence in some people, and what you can do to keep your digestive system happy while still hitting your protein goals.

The Science Behind ‘Protein Farts’

Protein farts are a real phenomenon, but the term is a bit misleading, says Danielle Gaffen, RDN, a San Diego–based registered dietitian–nutritionist and the founder of Eat Well Crohn’s Colitis, which provides personalized nutrition counseling for people living with inflammatory bowel disease (IBD) and other digestive conditions.

“It’s not protein itself directly causing gas. It’s what happens when protein isn’t fully digested and reaches the colon where it’s fermented by gut bacteria,” she says.

“But the odor, which is what people typically notice, comes from the breakdown of sulfur-containing amino acids like cysteine and methionine,” Gaffen says.

That said, simply eating more protein doesn’t automatically mean you’ll encounter digestive symptoms. The amount, source of protein, and other ingredients all matter, too.

Common Culprits: It Might Not Be the Protein Itself

In many cases, the protein fart problem has less to do with protein and more to do with the ingredients that often accompany high-protein foods and supplements, says Elena Ivanina, DO, a New York City–based gastroenterologist and the founder of the Center for Integrative Gut Health.

Here are some common culprits.

Dairy

Sugar Alcohols and Added Fibers

Protein bars may also contain ingredients that are notorious for causing digestive upset.

“This is a really important piece of the puzzle,” Gaffen says. “When someone tells me they feel gassy after eating a protein bar, I don’t jump straight to the protein, I look at the ingredient list. Often, it’s these artificial sweeteners or specific types of added fibers driving the symptoms,” she says.

Added fibers can also be problematic. Ingredients like chicory root, inulin, fructooligosaccharides (FOS), and maltodextrin are commonly added to protein bars to boost fiber content. But they can trigger bloating and gas, especially in people with irritable bowel syndrome (IBS), Ivanina says.

Low Carbohydrate Intake

“In that sense, you can see a pattern of what people describe as ‘gas-producing constipation,’” Gaffen says.

Animal vs. Plant Protein: Which Is Worse for Gas?

Both animal and plant proteins can cause gassiness, but in different ways. “In general, animal proteins — like meat, eggs, and even dairy if someone isn’t lactose intolerant — are very well digested and absorbed in the small intestine, so they tend to produce less gas overall,” says Gaffen. “However, when they do contribute to gas, it’s often more noticeable in odor.”

“Plant proteins also have lower digestibility in the small intestine compared to animal protein, so more reaches the colon for fermentation,” she says.

Gaffen advises her patients to look at animal and plant sources from a wider lens, accounting for their dietary preferences, food intolerances, overall balance of protein and fiber, and what other ingredients are present, like lactose or additives.

“It’s not that one type of protein is universally ‘worse’ for gas, it really depends on what comes along with the protein and how it’s digested,” she says.

How to Reduce Protein-Related Gas

If your high-protein diet is causing symptoms like gas or bloating, a few adjustments may help.

• Increase protein gradually. Going from 50 grams (g) of protein daily to 140 g overnight can overwhelm your digestive system. Slowly increasing intake gives your body time to adjust, Ivanina says. “The colonic microbiome adapts over time,” she says.
• Spread protein throughout the day. Instead of eating a massive portion of protein all at once, distribute it across meals to “support more efficient digestion and absorption,” Gaffen says. This step reduces the chance that excess protein will reach the colon.
• Stay hydrated. Drinking enough water supports digestion and transit time, helping you stay regular with bowel movements, Ivanina says. The average healthy adult is getting enough water if they have about 92 ounces (oz) to 124 oz of liquid per day from all sources, including water, soda, coffee, juice, and other drinks.

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• Eat slowly. “Simple habits can go a long way,” Gaffen says, noting that chewing thoroughly, avoiding drinking protein shakes quickly, and being mindful of swallowing excess air can also help with limiting gas.

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• Check ingredient labels. If protein bars or shakes are causing problems, look for sugar alcohols, or added fibers like inulin or chicory root, which may be upsetting your digestive system, Gaffen says. Whey or casein protein often contains lactose, which may suggest lactose intolerance, too, she says. To err on the safe side, avoid these highly processed protein products and eat whole-food protein sources.
• Don't neglect fiber. Some people miss out on fiber by eating a high-protein diet, but a balanced diet with fruits, vegetables, legumes, and whole grains can support healthier digestion overall, Ivanina says.

When to See a Doctor

Occasional gas is totally normal, but painful, persistent, or worsening digestive symptoms shouldn’t be ignored, Gaffen says. She recommends seeing a healthcare provider if you experience:

• Unintentional weight loss
• Persistent diarrhea or constipation, or a noticeable change in bowel habits
• Severe or worsening abdominal pain
• Blood in the stool or black, tarry stools
• Ongoing bloating with distention that doesn’t improve
• Signs of malabsorption, like greasy or floating stools
• Fatigue or other symptoms of nutrient deficiencies

If you have any known digestive conditions, such as IBS or Crohn’s disease, any noticeable changes in symptoms warrant a follow-up with your gastroenterologist to rule out a flare or another underlying issue, Gaffen says.

And, for the general population, if symptoms seem tied to specific foods, like dairy or wheat, seek advice from your healthcare provider, too. “Something like lactose intolerance can be identified and managed pretty easily. It’s helpful to have clarity,” she says.

The Takeaway

• So-called “protein farts” are real, and they’re often caused by undigested protein fermenting in the colon, leading to digestive symptoms like gas, bloating and abdominal pain.
• Issues like low fiber intake, lactose intolerance, and relying on ultra-processed sources of protein like protein bars and shakes can also be why protein is connected to excessive gas.
• Gradually increasing protein intake, spacing protein-rich foods throughout the day, staying hydrated, and eating enough fiber may help reduce gas and support healthier digestion overall.