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Gassy on a Plant-Based Diet? Study Suggests That May Be a Good Sign

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Key Takeaways

  • Researchers found that increasing fiber through a plant-based diet can affect the creation of gas in the digestive system.
  • This result may be uncomfortable, but it should be considered a sign of better health, researchers suggest.
  • There are ways to minimize this effect, experts note, especially increasing fiber on a more gradual basis.

If you have recently switched to a plant-based diet that includes more whole grains, fruits, and vegetables, it is possible you are experiencing an increase in digestive changes.

A recent study in the journal Nutrients suggests that it is not only common but also a good sign of better health to experience flatulence on this type of meal plan. In fact, being gassier could be related to more plant material in the digestive system.

About the Study

Researchers recruited 18 healthy, adult male volunteers. The volunteers ate a Western-style high in processed carbs and low in fiber for two weeks, and they ate a plant-based Mediterranean diet for two weeks. The order of the specialty diets was randomized. Each specialized diet was preceded by two weeks of a balanced "washout" diet to ensure participants' bowels were in the same state at the start of each study period.

Before, during, and after the study periods, participants’ stool composition and frequency were assessed. They also assessed the frequency of flatulence. After the plant-based weeks, the participants did not increase how often they had bowel movements, but their stool sizes doubled. They also a much more frequent flatulence during the day and a larger amount of gas after mealtime.

Although the gassy outcome might be uncomfortable, researchers concluded it was due to a significant increase in beneficial bacterial growth and more plant material in the digestive system. In order to process those foods, the bacteria kicked off fermentation, which produces gas as a side effect.

Importance of Fiber

Although the recent study had significant limitations because of its very small participant size, other research has also suggested that high-fiber diets could have considerable effects on gut health.

For example, a recent study in the journal mSystems reported beneficial changes in the digestive system microbiome after only two weeks on a diet focused on vegetables, fruits, and whole grains. In that research, participants ate about 40 to 50 grams of fiber per day, which is higher than the current recommendations from the Food and Drug Administration for 28 grams daily.

Katrine Whiteson, PhD

Lack of fiber intake in the industrialized world is starving our gut microbes, with important health consequences.

— Katrine Whiteson, PhD

However, most people in the U.S. only average about 15 grams per day, with consumption steadily decreasing over the last century, according to Katrine Whiteson, PhD, associate professor of molecular biology and biochemistry at the University of California Irvine.

“Lack of fiber intake in the industrialized world is starving our gut microbes, with important health consequences,” she says.

Not only can that affect digestive function, but improved gut health has also been shown to lower colorectal cancer risk, improve immune function response, and lower autoimmune disease prevalence. It also can boost mood, lower depression symptoms, and improve inflammation throughout the body.

In addition to increasing the amount of fiber overall, Dr. Whiteson emphasizes that plant diversity is also crucial. A research review in Molecular Metabolism noted that a healthy microbiome depends on an array of different beneficial bacteria types.

In fact, a diverse diet will create a diverse microbiome. The benefit there, the researchers add, is that bacteria will be more adaptable and less prone to the disruption that can lead to poor health outcomes.

Slow and Steady

One notable finding in the most recent study was that participants who already had a great deal of diversity in their gut bacteria did not have as much of a ramp-up with flatulence. That implies the gassy effect is likely a short-term adjustment to higher-fiber foods.

Tamara Duker Freuman, RD

When you add a lot of healthy options to your diet, especially with fiber, it can cause digestive issues if you try to do too much, too soon.

— Tamara Duker Freuman, RD

It is possible that the short amount of time given for the switch from the default diet to the high-fiber diet resulted in a more dramatic effect in terms of gassy results because there was no adjustment time.

That is a common issue with people who switch to more fiber abruptly, according to dietitian Tamara Duker Freuman, RD, who focuses on the dietary management of digestive and metabolic diseases and authored The Bloated Belly Whisperer.

“When you add a lot of healthy options to your diet—especially with fiber—it can cause digestive issues if you try to do too much, too soon,” Freuman says.

That can lead to more gas, and also general discomfort, bloating, and in more extreme cases, abdominal cramping and diarrhea. A better strategy is to increase these foods gradually over a matter of weeks or even months, she suggests. It is especially important to be cautious with "nutritious" processed options like bean pastas, cauliflower crusts, and nut flours.

“People tend to forget to include these in assessing their fiber intake,” she says. “But they can be considerable, in terms of how much you’re consuming daily.”

Although recent research suggests flatulence may be a sign your gut health is getting on track, you should not suffer through it. Freuman says when the gas becomes uncomfortable, you may need to slow down your fiber-rich dietary changes so your body has more time to adjust.

What This Means For You

A pivot toward more plant-based eating can be beneficial for your gut, but that means it could increase gas and other effects. Take a gradual approach instead, so your body can adjust to higher fiber amounts. And if your flatulence is particularly uncomfortable, you may want to reach out to a healthcare provider with your concerns.

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5 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Barber C, Mego M, Sabater C, et al. Differential effects of Western and Mediterranean-type diets on gut microbiota: a metagenomics and metabolomics approachNutrients. 2021;13(8):2638. doi:10.3390/nu13082638

  2. Oliver A, Chase AB, Weihe C, et al. High-fiber, whole-food dietary intervention alters the human gut microbiome but not fecal short-chain fatty acids. mSystems. 2021;6(2):e00115-21. doi:10.1128/mSystems.00115-21

  3. U.S. Food & Drug Administration. Daily value on the new nutrition and supplement facts labels. Updated May 5, 2020.

  4. Mohajeri MH, Brummer RJM, Rastall RA, et al. The role of the microbiome for human health: from basic science to clinical applications. Eur J Nutr. 2018;57(Suppl 1):1-14. doi:10.1007/s00394-018-1703-4

  5. Heiman ML, Greenway FL. A healthy gastrointestinal microbiome is dependent on dietary diversityMol Metab. 2016;5(5):317-320. doi:10.1016/j.molmet.2016.02.005