Maybe it’s the hummus platter at your favorite Mediterranean restaurant, or the cauliflower-and-broccoli side at your supermarket. Most of us are aware of our problem foods—stuff we’d eat all the time if it didn’t make us so gassy.
If you’ve ever wondered where that gas comes from and whether it’s bad for you, the answers may surprise you.
“Gas is the byproduct of the activity of the gut microbiota that live in our large bowel,” says Jane Muir, an associate professor of gastroenterology and head of translational nutrition science at Monash University in Australia.
The human gut is packed with trillions of bacteria, which are known collectively as the microbiome. Without these bacteria, your body couldn’t adequately break down and absorb all the nutrients you need to survive. But while these bacteria are located throughout your gastrointestinal tract, their numbers increase exponentially in your large intestine, Muir says.
Stuff that you can’t easily digest—mostly fiber-rich plant compounds—tend to slide through your GI tract until they reach your large intestine. Once there, your bacteria chow down on these indigestibles and produce gas (along with nutrients your body can access). “This is natural and normal part of bowel function,” Muir says.
Foods that commonly cause gas contain compounds called fructans—found in wheat, onion, artichokes and rye, to name a few—and also the galacto-oligosaccharides found in legumes, nuts and seeds, Muir says.
But the types of foods that produce gas vary from person to person, says Dr. Steven Zeisel, a professor of nutrition and director of the Nutrition Research Institute at the University of North Carolina. He explains that some people lack gut enzymes needed to digest certain nutrients, which may allow more of those foods to slip through to the bacteria in the large intestine. “Eating too much or too quickly can also overload the system and deliver more food down there to the bacteria, which generates gas,” he says.
“This gas and bloating may be uncomfortable,” he says. “But it’s not harmful.”
That said, there are some gut-related ailments that may feature gas as a side effect. For people who are lactose intolerant—a condition that stems from the lack of a digestive enzyme needed to break down milk sugars—eating dairy can produce gas and bloating, as well as diarrhea, stomachaches and vomiting. And if you’ve been sick, you may find that your system produces more gas than usual. “You can temporarily lose the ability to absorb certain nutrients, and so more stuff makes it down to the bacteria in the colon,” Zeisel says. That leads to more gas and, in some cases, diarrhea. In those situations, you don’t want to aggravate what ails you with more of your problem foods.
But if you’re healthy and dealing with run-of-the-mill gas, there are some ways to avoid it that don’t entail skipping your favorite bean dip.
Zeisel mentions over-the-counter anti-gas supplements like Beano. These products contain enzymes that help your body break down gas-producing foods before they can reach the bacteria in your large intestine. “They’re not 100% effective, but they do work, and they’re safe to take every day,” he says. There are also similar products for people who struggle with lactose or other common dietary gas-producers.
Another option: Every day, eat small portions of the foods that give you gas. “This builds up the population of bacteria that can process them, resulting in greater adaptation and so less gas,” Muir says.
She explains that the composition of your diet can shift the bacterial makeup of your microbiome. Eat healthy fiber-loaded foods, and over time your microbiome should evolve in ways that reduce your gas production. (Because these foods promote the growth of healthy bacteria, they’re known as “prebiotics,” she says.)
Beans may always leave you a little overinflated. But rest assured that your gas isn’t harming your health.