Why Does Protein Make You Fart?
Fast Facts
- Protein farts are a common side effect of consuming protein.
- The type and amount of protein you eat are the biggest predictors of how gassy you’ll be.
- Picking the right proteins can reduce the smelliness of your emissions.
Nutrition experts and Reddit bro scientists agree on at least one thing—protein produces gains. Strip steaks and hard boiled eggs fuel muscle growth, but they often come with a downside: Protein farts can be so smelly they put your week-old gym socks to shame.
There’s no evidence that protein itself increases flatulence, says Mike Shea, R.D. and founder of Hierarchy Nutrition. But it can make your farts stink. So why does protein make you fart? How can you prevent protein shakes from making you fart? Here’s what you need to know.
Why Does Protein Make You Fart?
Some proteins contain sulfur, which creates eye-watering gas when you metabolize and digest it. Others create noxious emissions when they ferment in your gut.
The best way to avoid excessively rank bouts of gassiness: Eat the right proteins that contain the right compounds, in the right amounts.
Animal and plant protein sources contain different compounds that may contribute to how often you pass gas, and the rancid smell that follows.
Animal Protein
Meats and eggs
Turkey, beef, eggs, and chicken contain sulfur, a mineral that is needed to produce insulin, and make collagen and keratin (a protein that helps form and strengthen hair, nails, and the outer layer of skin).
Sulfur is also essential for making and recycling glutathione–a critical antioxidant that may help reduce inflammation and prevent cell damage caused by oxidative stress (1,2).
When you digest and metabolize animal proteins that contain sulfur, that gives the rotten egg smell and can contribute to gas production, says Shea.
Next thing you know you’re ripping farts that smell like rotten eggs.
Certain essential amino acids found in animal protein, like methionine, also contain sulfur, Shea says. The sulfur in these amino acids also contributes to gas production.
Dairy
Milk, yogurt, and some dairy-based protein powders like some brands of whey concentrate and casein have amounts of lactose, a sugar found in milk.
If your small intestine doesn’t make enough lactase–a digestive enzyme that breaks down lactose so your body can absorb it–lactose is passed to your large intestine where bacteria digest the sugars by fermentation, making you gassy and bloated. When that trapped air comes out, it’s potent.
Flavored animal-based protein powders (looking at you Fruity Pebbles and Cinnamon French Toast) and bars pack a double gas punch because they’re often sweetened with sugar alcohols like sorbitol, mannitol, and xylitol. These low-calorie flavor-enhancers are tough for your gut to break down.
“Because they’re hard to digest, they end up in your large intestine where your gut bacteria have to break them down,” Shea says. “This leads to bloating and gas.”
Plant Protein
Plant protein sources like chickpeas, lentils, and beans contain short-chain carbs. They can pass through your stomach and be poorly absorbed by the small intestine. When they make their way to your large intestine, the gut bacteria ferment these to use as fuel and the process produces gases like hydrogen, carbon dioxide, and methane. Some of these gases are absorbed, some are expelled through breathing, some are recycled by bacteria, others have no choice but to come out your rear end.
The soluble fiber found in plant foods such as oats is a type of fiber that dissolves in water to form a gel-like substance that slows down digestion, and is more fermentable so may increase gas.
You’re less likely to experience gas from plant-based protein powders than you would from whole food plant sources, because the soluble fiber has been extracted during processing, says Shea.
That said, if your plant-based powder contains sugar alcohols for added flavoring, it can trigger your protein flatulence, Shea adds.
How Do I Get Rid of Protein Farts?
Change your protein powder
If you’re a fan of whey protein, choose whey isolate.
“Whey isolate protein contains less lactose, carbohydrates, and fat than whey concentrate,” Shea says.
If you struggle to digest lactose, that can be a game-changer.
Even some people who are lactose intolerant can often handle a whey isolate, Shea says.
If dairy doesn’t sit right with you, try a lactose-free plant-based protein powder, like pea protein. An added bonus: your protein intake won’t suffer. One scoop of pea protein isolate powder has up to 20 grams of protein for every 100 calories—close to the amount in most whey isolate powders.
Whether you’re going with a whey isolate or pea protein powder, look for brands without sugar alcohols such as Bad Athletics and KOS.
Add herbs to your diet
Some herbs may help soothe and tame your gassy gut. In a growing number of studies, peppermint helped calm stomach muscles and relieved indigestion and gas. Ginger may improve digestion so food doesn’t hang out in your gut and ferment and get gassy.
Try psyllium husk
Psyllium husk–a fiber that soaks up water in your gut and helps you stay regular—may reduce gas, says Shea.
A small study published in the journal Gut showed psyllium reduced inulin-related gas production in 19 people with irritable bowel syndrome (IBS), although it did not directly slow down fermentation (3).
Eliminate gas-inducing carbs
A high protein intake isn’t the only thing that may trigger nasty smelling farts.
Some carbs contain sugars like fructose (found in some breakfast cereals with whole wheat and oats) and raffinose (beans have large amounts while cruciferous veggies like broccoli, asparagus, and Brussel sprouts have smaller amounts). If you lack efficiently functioning digestive enzymes to digest these sugars, you can end up bloated and gassy. In tandem with too much protein, you may as well be an exhaust pipe blowing out fumes.
If you feel gassy after eating these foods, try Beano, a dietary supplement that contains an enzyme to help you break down carbohydrates making them easier to digest.
Don’t race through meals
When you inhale your food, or down your protein shake in one gulp, you take in extra air. If you’re not burping this out, there’s only one other way for it to come out.
“Eat slowly and close your mouth while you chew. This reduces how much air you take in and decreases your chances of flatulence,” Shea says.
Find your right protein dose
When people change their diet or exercise routine, they tend to overdo it on protein, especially protein powders, Shea says.
Protein powders are often overconsumed and if you eat more protein than your body needs, protein farts can follow. A general protein rule of thumb is to eat 1 gram per pound of bodyweight per day. For a 180-pound guy, that works out to be around 180 grams of protein per day.
If you’re more visual, the palm of your hand is about 25 to 30 grams of protein, Shea says. That same 180-pound guy would need about 7 to 8 palms worth of protein.
Spread your protein intake out between 4 to 6 smaller, more consistent meals throughout the day, especially if you’re looking to build more muscle while limiting gas.
For gym gains, “you want a steady intake of amino acids periodically throughout your day,” says Shea. “Leucine is in all animal proteins and is a catalyst to muscle protein synthesis which signals growth and muscle repair.”
Leucine is more abundant in animal proteins than plant sources because plant-based proteins have less essential amino acids content overall (4,5). If you’re vegan, or made the switch to a plant-based powder, leucine supplements may help maximize muscle growth.
Are Protein Farts a Problem?
Protein farts are more of an embarrassing nuisance than a health problem. If you change your protein powder, add herbs to your diet, eat slowly, and watch your protein intake, it may end your flatulence nightmare.
If you still experience protein farts and they come with symptoms like bloating, cramps, abdominal pain, and diarrhea, see your doctor or consult a gastroenterologist, Shea says. You may have a digestive condition like lactose intolerance or IBS that requires more medical advice.
The Bottom Line
Protein is an essential macronutrient you can’t live without, but eating too much of certain types may lead to increased, bad-smelling gas. Changes to your diet and protein intake can reduce flatulence and any potential embarrassment without sacrificing your gains.
References
1. Ingenbleek, Y. and Kimura, H. (2013). Nutritional essentiality of sulfur in health and disease.
2. Minich, D. and Brown, B. (2019). A Review of Dietary (Phyto)Nutrients for Glutathione Support.
3. Gunn, D.; et al. (2021). Psyllium reduces inulin-induced colonic gas production in IBS: MRI and in vitro fermentation studies.
4. Tessier, A. and Chevalier, S. (2018). An Update on Protein, Leucine, Omega-3 Fatty Acids, and Vitamin D in the Prevention and Treatment of Sarcopenia and Functional Decline.
5. Berrazaga, I.; et al. (2019). The Role of the Anabolic Properties of Plant- versus Animal-Based Protein Sources in Supporting Muscle Mass Maintenance: A Critical Review.
