Why Does Protein Give You Gas?

And how low protein days could be beneficial.

Via Canva

You know how everyone loves that person who can fumigate an entire room after they’ve had a protein shake? Maybe you’re that person in your friend group or household. Maybe someone you love is constantly “passing gas” causing you to seek shelter beneath your shirt. Or maybe mom just made her famous chili and you have a 4-hour flight home the next day and you’re already planning on blaming it on the baby in the seat behind you.

What is it about protein shakes, or even just high protein meals that can sometimes leave us full of gas? Why is it that every time I eat Mom’s chili it’s only a matter of time before the rest of the world knows? Does having gas mean something not good is going on? What are some remedies to help address this engine-blowing issue?

Gas Creation

No, not the product from Shell Oil that lets you drive around, but rather the gas and subsequent flatulence that our own body creates. Gas in the gut comes from four sources: 1) Swallowed air and air mixed with food, 2) Bacterial fermentation of food products, 3) Chemical reactions in the gut (food mixing with digestive juices), and 4) Diffusion of gases from the bloodstream (Levitt et al, 1970). For our purposes, we’re going to be referring to mostly numbers 2 & 3, as 75% of gas creation comes from bacterial fermentation (Hasler, 2006).

Once you have a buildup of gas, sometimes it just becomes too uncomfortable to handle, and you feel like you have to let it out. Fortunately, most of us have a pretty high tolerance of gas build-up before we start to experience abdominal pain or discomfort (Serra et al, 1998). The human body is also tremendous at clearing gas, evident in the previously cited study where researchers infused gas into healthy subjects (imagine that plane ride) in a dose-dependent manner, and saw a dose-dependent gas clearance (aka the people who had more gas infused in them excreted more gas out).

Gas commonly occurs after a meal, as solid and liquid ingestion accelerate the passage of gas through the digestive tract. The major gases in flatus (fancy medical term for farts) are Hydrogen, Methane, Oxygen, Carbon Dioxide and Nitrogen. Hydrogen Sulfide is a less commonly produced gas, but when it is you and everyone around you sure knows about it (Hydrogen Sulfide produces that classic ‘rotten egg’ smell).

Protein Digestion

Some people see gas after a high protein meal as a signal that the protein was not digested well… sort of. Protein consists of peptides and amino acids bonded together (amino acids are the building blocks for protein). Once you’ve had protein and it reaches the stomach, Hydrochloric Acid (HCl) is released, which ‘turns on’ an enzyme called Pepsin to start breaking down the protein. Once that partially digested protein reaches the small intestine (SI), the pancreas secretes more enzymes to further break down the protein into single amino acids, or several amino acids still bonded together (Tri- and Dipeptides). From this point the amino acids should be absorbed in the small intestine.

Sometimes, for reasons we will discuss shortly, undigested protein is not absorbed in the SI and makes its way to the large Intestine (LI). From there, the ‘protein remnants’ can be fermented by our gut bacteria. Gut bacteria, particularly in the LI, normally ferment carbohydrates (dietary fiber and resistant starches) as fuel. When our gut bacteria start to ferment protein rather than carbohydrates, some questionable compounds are made: ammonia, phenols, amines, and the previously mentioned Hydrogen Sulfide gas (Yao et al, 2016).

That is one of my concerns over the new craze of the carnivore diet, as we don’t have any long term data on the effects of really high protein consumption (greater than 50% of calories) on the gut microbiome. Quick side note, I’ve done a carnivore diet, and it can be done right with proper attention to consuming organ meats, a collagen source, and a quality fat source.

What’s Causing These Digestive Issues

As I previously mentioned, under ideal conditions, much of our protein would be properly broken down and then absorbed before making its way to the large intestine. To understand where problems arise, let’s reverse engineer and think back to how protein is digested. It starts in the stomach with HCl, so anything that causes low stomach acid (hypochlorhydria) such as acid-suppressing medications (Prilosec OTC, Omeprazole, Tums, H2 Blockers), H. Pylori infection, Pernicious Anemia and Autoimmune Gastritis (autoimmunity to cells in the stomach that produce HCl), and gastric bypass surgery can impair protein digestion.

Pancreatic enzymes are also needed. Chronic pancreatitis (from alcoholism, certain medications, kidney failure, gallstones) and pancreatic insufficiency (from digestive conditions such as celiac, Crohn’s, Ulcerative Colitis, IBS) can impair protein digestion. There’ s even some evidence that Type II diabetics on Insulin see a reduction in the size of their pancreas, along with decreased enzyme production (Silva et al, 1993).

If you’re someone who’s been diagnosed with any of the above conditions, make sure you are speaking with your primary care provider about your treatment options. If you’re looking for protein digestion support, stay tuned for the next section, but I’d also recommend seeking out a practitioner with knowledge and experience in using nutritional and lifestyle support for overall digestion.

Support Options

Naturally when people hear they are not producing enough of x, y, or z enzyme in the body, the logical next thought is, “I’ll just take it as a supplement!” In those with chronic pancreatitis (as a result of a rare genetic condition called Cystic Fibrosis), adding extra proteases (enzymes meant to break down protein) increased protein digestion and made their stools less odorous (Morrison et al, 1992).

Gluten, the protein present in wheat, barley, and rye, is often touted as being problematic for many people. There are some commercial products that are marketed as being able to breakdown gluten and help with gluten intolerance/sensitivity issues, however research appears to show these supplements may be unsuccessful (Janssen et al, 2015). If you want to know more about the risks/benefits of gluten consumption, particularly for those with autoimmune conditions, check out this article.

Unfortunately, there isn’t any research using supplemental stomach acid (Betaine HCl) alone on humans, but anecdotally lots of natural medicine practitioners report their patients having better digestive function, including less gas, with using HCL and digestive enzymes. A couple of brands I recommend include Thorne, Functional Medicine Formulations, and Apex.

If you find yourself struggling with digesting protein, I’d recommend experimenting with doing low protein days, especially if you constantly eat high protein. I personally consume roughly 150–200 grams of protein per day, so once a week I’ll do a low protein day of less than 30–40 grams per day. Ideally, this will give your digestive system a break from constantly having to digest protein. If you think about it, our ancestors probably weren’t eating the same exact foods every day. Their diet would vary based on what was available to them, sometimes that would be low protein and high vegetables.

Constantly having gas can really take away from one’s quality of life, not to mention making some public outings awkward if you were to ever ‘let one rip.’ But know that gas isn’t something that should happen all the time, and that there is a way to live gas-free. If you’re struggling with a chronic gas problem, I’d recommend seeking out a natural/functional/alternative practitioner or medical doctor who has experience in supporting patients’ digestive function.

As always, Trust in Your Gut.

Disclaimer: This is not meant to convey medical advice, if you’re looking for such, please consult a qualified medical practitioner.


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Levitt MD, Bond JH Jr. Volume, composition, and source of intestinal gas. Gastroenterology. 1970 Dec;59(6):921–9. PMID: 5486278.

Janssen G, Christis C, Kooy-Winkelaar Y, Edens L, Smith D, van Veelen P, et al. Ineffective Degradation of Immunogenic Gluten Epitopes by Currently Available Digestive Enzyme Supplements. PLoS ONE. 2015 10(6): e0128065. doi:10.1371/journal.pone.0128065

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Educating, Optimizing, & Empowering Fitness Enthusiasts To Trust In Their Gut. Doctor of Chiropractic. Instagram: @drnickbelden. LinkedIn: Nicholas Belden