Protein is a double-edged sword: it fills you up and rebuilds your muscles after a tough workout, but it can also leave you with rank, room-clearing farts.
If you drink tons of protein shakes or have ever tried the keto diet, you know firsthand that protein farts are a thing — and if you haven’t experienced them yourself, you’ve likely smelled one wafting your way at the gym. They’re a major topic of discussion on fitness blogs, and there are (multiple) lengthy Reddit threads devoted to the topics of cause and prevention.
It’s enough to make you rethink your nutritional strategy — but the truth is, you don’t have to cut down on your protein shakes to curb your flatulence. You likely just have to make a few small tweaks to your diet. We asked a few nutritionists and dietitians to explain.
WHAT CAUSES PROTEIN FARTS?
For the most part, the cause of protein farts isn’t that complicated: you’re probably just eating too much of it.
If you’re eating normal amounts of protein (about one gram per kilogram of body weight), “it will all be broken down in the small intestine into amino acids, which are absorbed into the bloodstream,” explains Kate Scarlata, R.D., author of The Low-FODMAP Diet Step by Step. Amino acids — the building blocks of protein — then help to build muscle, bone, cartilage, and blood.
But if you’re consuming lots of protein, it scoots right down to your colon, where gut microbes start to feast on it. That results in your body producing hydrogen sulfide gas (a.k.a. that sulfur-y, rotten egg fart smell), Scarlata says.
Protein shakes and smoothies can be particularly problematic, because some people are particularly sensitive to the milk proteins casein and whey, says Ryan Maciel, R.D., C.S.C.S., a dietitian based in Boston, MA. Whey (as well as milk, cheese, or yogurt) is chock-full of lactose, which is a major factor in contributing to flatulence. This is true even if you’re not lactose intolerant: in fact, 65% of people have issues with digesting dairy.
Sugar alcohols (xylitol, sorbitol, mannitol), high fructose corn syrup, and a food additive called carrageenan are also often found in protein shakes and bars, which can contribute to your protein farts, he notes.
Then there’s your meat. Most animal proteins (eggs, beef, pork, poultry, and fish) contain sulfur, which can contribute to the nasty smell, says Maciel. If you’re vegetarian or vegan, even plant-based sources of protein, such as beans, soy, and lentils, can cause digestive problems, thanks to short-chain carbohydrates called oligosaccharides that are also fermented by the bacteria in your gut, says Maciel.
HOW DO YOU GET RID OF PROTEIN FARTS?
While passing some gas is totally normal and healthy, if you’re noticing bloating, diarrhea, or constipation regularly, you should touch base with your doctor, says Scarlata. There’s also a possibility that your protein farts isn’t just resulting in toxic smells: Scarlata says that the gut microbes that feast on protein also produce small amounts of toxic metabolites, which have been linked to the intestinal inflammation that causes gastrointestinal issues like Irritable Bowel Syndrome.
To cut back on cutting cheese, limit your protein intake to the recommended 1 gram per kilogram of body weight. (For a 200-pound person, that would be about 90 grams of protein.) If you’re an endurance athlete or weight-lifter, you might need 10 or so more grams, Scarlata notes, but don’t overdo it.
You should also eat more foods with fiber, such as a baked potato with skin, brown rice, or quinoa.“Our gut microbes prefer eating the fibers that arrive in the colon from these foods first and will create less hydrogen sulfide gas,” she says.
If lactose or dairy bother you, look for lactose-free protein powders (brown rice protein or whey protein isolate) for relief. (Try Garden of Life vegan protein powder, $32.89). Maciel also suggests taking probiotics with strains of Bifidobacterium, Lactobacillus, and Streptococcus. “These strains seem to help reduce symptoms of irritable bowel syndrome,” he says.
Otherwise, just cross your fingers and hope you can squeak out a silent one. Or just own it like these guys. Either one.