Ask the doctors: Vegan diet causes increased intestinal gas

Dear Doctors: I am a vegan, and after a meal, I have uncomfortable and smelly intestinal gas. It has only ever eased when I took an antibiotic and after colonoscopy prep. I assume that’s because these killed my gut bacteria. Is there a fast way to reset the gut? Is this problem a health risk?

Dear Reader: The gut microbiome refers to the remarkable and complex ecosystem of trillions of bacteria, fungi, viruses and other microorganisms in our gut. While some are found in the small intestine, the vast majority live in the large intestine. Research continues to uncover ways that the composition, diversity and health of these colonies of microorganisms affect our health.The microbes we hosthave a direct influence on diverseprocesses such as digestion, nutrient absorption, cardiovascular and neural health, immune response and even brain health and function.

You are correct that A primary cause of intestinal gas is the metabolic activity of bacteria in the gut. It has to do with It has to do with dietary fiber, a complex carbohydrate. Unlike simple carbs, which get absorbed into the bloodstream in the small intestine, Fiber passes undigested into the colon, or large intestine. There, the cellulose, pectin, lignin, hemicellulose, mucilage and other cell remnants that survived the digestive process become food for the resident bacteria.

First, enzymes produced by the bacteria dismantle the complex carbs. Then, through fermentation, the resulting simple sugars get processed into short-chain fatty acids the bacteria can absorb. One of the byproducts of that fermentation is intestinal gas.

In your case, several considerations come to mind.

As a plant-forward vegan, your diet contains a significant amount of plant-based fiber. Cruciferous vegetables such as broccoli, cabbage and cauliflower; foods that contain sulfur such as garlic and onions; and beans and legumes are associated with robust and sometimes smelly gas production. Some vegans who experience excessive gas like to subtract, then gradually reintroduce foods to help identify any that may be problematic. Some people then choose to limit or eliminate those foods.

It’s true that antibiotics and colonoscopy prep can significantly alter the balance of intestinal flora. Research shows that, when used only occasionally, antibiotics don’t cause lasting damage. Gut recovery can take anywhere from several weeks to a few months. You can boost your gut recovery by eating dietary fiber from a wide range of sources. This can also temporarily increase intestinal gas.

Excessive gas production is not a health risk. It can sometimes be a symptom of an underlying disease or condition such as Crohn’s disease, irritable bowel syndrome (IBS), ulcerative colitis or small intestinal bowel overgrowth (SIBO). If changes to your diet don’t have a beneficial effect on gas production, check in with your health care provider for guidance.

Send your questions to askthedoctors@mednet.ucla.edu.