Why am I so Gassy?
by Adam Rinde, ND
Experiencing bloating, burping, or flatulence is a common and temporary issue for many individuals. However, if these symptoms persist for days or weeks, they can become alarming and concerning for those seeking answers. First, it is essential to recognize that intestinal gas is normal; we wouldn't survive without it. Understanding that humans produce significant amounts of gas and other organic compounds is also crucial. Gas-producing volatile organic compounds (VOCs) arise in the body due to inflammation and oxidative stress during both normal and abnormal metabolic processes. VOCs can also originate from external sources such as food, medications, and microbes. They are excreted and can be detected in urine, skin, blood, feces, and exhaled breath. More than 1,000 VOCs can be identified in breath samples. In certain conditions like IBS, IBD, and SIBO, the production of these volatile compounds may indicate dysfunction. Only three gases are measured in clinical settings to diagnose gas-related issues: breath hydrogen sulfide, breath methane, and breath hydrogen. However, a field of study known as Volatomics examines over 1,000 VOCs produced by humans and the relationships these gases have with various disease states. For instance, studies have indicated that only one compound (1-methyl-4-propan-2-ylcyclohexa-1,4-diene) exhibited elevated levels in fecal and breath samples when comparing IBS patients to healthy individuals. In cases of Crohn's disease, propan-1-ol was found to be elevated in feces and breath across four studies.
Most of the gas in our intestines is nitrogen (N2), while the rest consists of oxygen (O2), carbon dioxide (CO2), hydrogen (H2), methane (CH4), and hydrogen sulfide (H2S).
Oxygen is usually the lowest represented gas and Nitrogen is the highest.
The stomach has predominantly odorless gas of Nitrogen and Oxygen. Whereas the colonic gas contains predominantly the odorless gas of Methane and O2.
Odor from flatulence/belching usually comes from sulfur-containing compounds such as methanethiol, dimethyl sulfide, hydrogen sulfide, as well as short-chain fatty acids, skatoles, indoles, volatile amines, and ammonia.
When excessive intestinal gas does occur there may be several causes:
We typically have around 200 ml of intestinal gas. Oxygen is usually the least-represented gas, while nitrogen is the most abundant. The stomach's predominantly odorless gas mixture consists of nitrogen and oxygen, whereas the gas in the colon mainly contains methane and O2. The odor from flatulence or belching usually arises from sulfur-containing compounds such as methanethiol, dimethyl sulfide, and hydrogen sulfide, in addition to short-chain fatty acids, skatoles, indoles, volatile amines, and ammonia.
When excessive intestinal gas occurs, several factors may contribute:
• Consumption of rapidly fermentable foods and nonabsorbable items like dietary fiber and resistant starches. (more on this below)
• Malabsorption disorders such as SIBO, dysbiosis, celiac disease, sucrose intolerance, lactose intolerance, and fructose intolerance.
• Excessively high-protein diets can cause this due to the agonism of the GLP-1 receptor, which slows motility.
• Insufficient digestive functions may include pancreatic enzymes, brush border enzymes, bile, and adequate stomach and intestinal pH levels.
• Excess air swallowing, which may occur from activities like drinking through a straw, chewing gum, consuming carbonated beverages, gulping food and drinks, smoking, and mouth breathing. This is often seen in individuals with anxiety.
• Disruption of the migrating motor complex, which typically occurs with irregular eating patterns, binge eating, purging, and grazing. It may also arise from post-infectious IBS.
• Decreased gas absorption due to impaired gas clearance from motility disruptions, such as in diabetes, scleroderma, pseudo-obstruction, and certain medications.
• Decreased gas absorption from obstructions like adhesions or intestinal or pelvic masses.
• Infections such as Giardia, H. pylori, or Clostridium difficile may lead to excess gas.
• Other more unusual causes are due expansion of gas due to changes in atmospheric pressure.
Dietary Factors
Hydrogen: Ingested carbohydrates and proteins are sources of H2 production. In healthy individuals, certain foods with high concentrations of oligosaccharides, such as stachyose and raffinose found in legumes, or resistant starches (flours made from wheat, oats, potatoes, and corn), cannot be completely digested by enzymes within the normal small bowel, leading to increased H2 production by resident microbes.
Hydrogen sulfide gas production has been linked to foods rich in dietary amino acids (cysteine, taurine, methionine). Foods rich in cysteine, taurine, and methionine rich foods consist of Beef, Eggs, Poultry, Soy/Tofu, Pork, Lamb Fish, Shrimp Tuna Salmon, Mollusks, Saturated Fats, and a few plant products like white beans, and Quinoa. (1)
Methane production by dietary factors is unclear. However, some links have been shown to fat consumption and/or fecal bile content. This means methane production seems to decrease if adequate bile acid excretion is performed in the colon. The presence of bile seems to lower methane production. Since many dietary and functional factors regulate bile production, this area is quite complicated. There is much to learn. 95% of Bile is normally reabsorbed in the last part of the small intestine, and the remaining 2-5% is sent to the colon for excretion. So right now, we may assume if there are low amounts of colonic bile, then methane gas is more likely to be produced. (2)
Microbial Production of Gas
In the gut, CO2 is produced from the digestion of fats and proteins in the upper gastrointestinal tract, as well as from bacterial fermentation of the digestive soup (intraluminal digestive material), or it may be released through the interaction of acid and bicarbonate. Most CO2 is absorbed by the body before it reaches the colon. However, if it is present in flatulence, it is likely due to bacterial fermentation occurring in the colon. Excessive CO2 in flatulence may result from an increased intake of non-digestible fiber that reaches the colon.
Hydrogen (H2) is both produced and consumed by our gut microbes. Two specific types of microbes are known to consume hydrogen gas. One is the methanogens from the Kingdom Archaea, which consume four molecules of hydrogen to produce one molecule of methane. The other consists of hydrogen sulfide-producing organisms, such as Desulfovibrio piger, which consume two molecules of hydrogen to produce one molecule of hydrogen sulfide. Additionally, acetate (a short-chain fatty acid) is produced through the consumption of hydrogen. The number of microbial producers of hydrogen is vast.
Hydrogen Sulfide producers include:
Desulfovibrio spp.
Salmonella spp.
Campylobacter jejuni
Citrobacter freundii
Aeromonas spp.
Morganella spp.
Proteus spp.
Pseudomonas aeruginosa
Yersinia enterocolitica
Hydrogen Producers include:
Streptococcus: primary colonizers of the human oral cavity
Escherichia coli: primary in the lower intestine
Staphylococcus species: primary colonizers of the upper respiratory tract and on the skin
Micrococcus: primary colonizers of the oral cavities, mucous membranes, and skin
Bacteroides: the most abundant phylum of the GI tract
Clostridium: primary colonizers of the intestinal tract, playing a crucial role in gut homeostasis by interacting with the other resident microbe populations.
Peptostreptococcus: the normal inhabitant of the healthy female reproductive tract, normal flora of the mouth, upper respiratory tract, intestinal tract, and skin
Enterococcus species: primary colonizers of the gastrointestinal tract.
Methane is thought to be produced primarily by Methanobacter smithii
How often should you experience flatulence? The frequency of flatus varies between 10 and 20 times a day in healthy individuals. However, the most common concern is the odor of the gas due to fear of embarrassment. Many often complain because gas production can be extremely uncomfortable and unpleasant, limiting their desire to eat and socialize. The unpleasant smell of flatulence mainly comes from sulfur-containing compounds, such as methanethiol, dimethyl sulfide, and hydrogen sulfide, along with short-chain fatty acids, skatoles, indoles, volatile amines, and ammonia. Hydrogen sulfide has a distinct egg-like odor. Ammonia production is a result of excessive protein putrefaction in the gut. Skatoles and indoles typically arise from bacterial dysbiosis or overgrowth.
What should you do if you feel that gas or flatulence is a problem for your health? It is important to undergo an exam and discuss all the potential causes with your primary care provider. If you seek further advice, consider consulting a functional medicine or naturopathic physician specializing in GI health or a comprehensive gastroenterologist. Tests are available, such as the Lactulose Hydrogen/Methane/Hydrogen sulfide test and Trio Smart. Additionally, VOC testing will soon be available as a biomarker. Stool and digestive testing can also aid in understanding imbalances. It is also crucial to mention any red flags, such as nighttime symptoms, pain, unexplained weight loss, blood in the stool, vomiting, and severe constipation.
sources:
Martha H Stipanuk, Metabolism of Sulfur-Containing Amino Acids: How the Body Copes with Excess Methionine, Cysteine, and Sulfide, The Journal of Nutrition, Volume 150, Issue Supplement_1, October 2020, Pages 2494S–2505S, https://doi.org/10.1093/jn/nxaa094
Florin TH, Woods HJ. Inhibition of methanogenesis by human bile. Gut. 1995 Sep;37(3):418-21. doi: 10.1136/gut.37.3.418. PMID: 7590441; PMCID: PMC1382826.
Van Malderen K, De Winter BY, De Man JG, De Schepper HU, Lamote K. Volatomics in inflammatory bowel disease and irritable bowel syndrome. EBioMedicine. 2020 Apr;54:102725. doi: 10.1016/j.ebiom.2020.102725. Epub 2020 Apr 21. PMID: 32330874; PMCID: PMC7177032.