November 9, 2019

Where does intestinal gas come from?

 It’s normal and healthy to produce some gas in the GI tract.  Many people who think they have excess gas actually fall within the normal range.  Gas in the intestines comes from the air we swallow and from bacterial fermentation of food, which happens with some foods during digestion and is meant to keep us healthy.

Do certain foods cause more bloating and gas?

Foods high in FODMAPs, which include artificial sweeteners, dairy, wheat and some fruits and vegetables, are poorly absorbed in the small intestine, osmotically active (they increase intestinal water content) and are quickly fermented by gut bacteria, leading to more gas production.  In patients with a sensitive gut (or in healthy people who happen to have a meal very high in FODMAPs), these foods can cause excess bloating and gas.  Read more about FODMAPs here.  People with specific food intolerances (like lactose or fructose) can also produce excess gas.

Should I stay away from fiber because of bloating and gas?

No.  In general, diets high in fiber from whole plant foods (like beans) are very healthy.  If a person who has consumed very little fiber suddenly starts eating lots of whole plant foods, he or she may initially experience more gas.  However, this symptom will improve with time.  Move to consuming a high-fiber diet gradually rather than suddenly.  In addition, food preparation methods like soaking legumes and grains can decrease bloating and gas.

Do certain types of foods cause smellier gas?

 Bacteria in the digestive system break down foods and generate byproducts, including sulfides which have an unpleasant stench.  Smelly gas typically comes from digesting a lot of sulfur-rich foods.  In a Western diet, the culprits are usually meat and eggs (hydrogen sulfide is called the “rotten egg gas”), with meat eaters generating much more sulfides than those eating plant-based.  But there are a few plant-based sulfur-rich foods, too, like garlic.

Can intestinal bacterial imbalances affect gas production?

Yes.  Patients with small intestinal bacterial overgrowth (SIBO) can suffer from excess gas and bloating.  So can those with other causes of an imbalanced gut microbiome, or bacterial “dysbiosis” with low bacterial diversity, such as frequent, excessive antibiotic use or a diet low in fiber and high in animal products (the Western diet).