“The Bacteria Made Me Do It”—Potential Causes of Flatulence

By Noelle Patno, PhD

The common complaints of bloating and flatulence, while not immediate reasons to go to the doctor, often create discomfort both individually and socially. There may be a great deal of information about intestinal gas that is considered “common sense,” but you may be interested to learn what research studies in this area have revealed. Let’s begin!

What causes intestinal gas?

If you’ve ever heard someone sing to you, “Beans, beans, the musical fruit, the more you eat, the more you toot,” you’re probably already familiar with several foods that can cause gas production and flatulence.

Certain foods are known to be metabolized by intestinal bacteria and generate gas.1 The gas within our digestive system consists mainly of nitrogen and oxygen. Foods composed of complex carbohydrates, including beans, and foods high in polysaccharides (particularly oligosaccharides such as inulin) tend to cause, or worsen, flatulence. When we digest these foods, gas, mainly in the form of hydrogen, methane, and carbon dioxide, is released.2

To reduce risk of excess intestinal gas, AVOID eating too much of these foods:

  • Beans, lentils, legumes including peanuts
  • Nuts
  • Dairy
  • Yeast in baked products
  • Cereals such as wheat or oats
  • Cruciferous vegetables like artichokes, broccoli, leeks, cauliflower, cabbage, garlic, onions, beans, Brussels sprouts, etc.
  • Indigestible foods—lactose, fructose, sorbitol, and certain fruits, vegetables, and legumes
  • Pork and proteins

While the many bacteria in the intestine produce gas from digesting the indigestible remnants of food that reach the lower intestine, there are other causes of gas,3 some associated with burping rather than flatulence. These include:

  • Swallowing air by itself or while gulping or swallowing food/liquids
  • Atmospheric pressure changes
  • Chewing gum
  • Smoking
  • Drinking carbonated beverages

It is normal to have gas and to pass it. But how much flatus is normal?

Understandably, flatulence is not among the most popular and well-studied scientific phenomena , but it’s interesting to note that the average number of times healthy people pass gas per day is around 10 to 14 times.4,5 Do you think you produce excessive gas? Track it. Maybe you need to find out just how normal you are!

Typically, people pass minor amounts of gas without noticing it—gentle release of the small pockets of air that may have been swallowed and small amounts made by bacteria—it even happens during sleep; larger volumes are typically released after meals6 (hint: plan accordingly!).

While flatulence releases intestinal gas, the problem of trapped gas found with bloating, according to the medical community,  is actually a problem of gas dynamics.3

Bloating—a problem of trapped gas, not excess gas

A recent analysis by computed tomography (CT) scans has identified that the average intestinal gas volume, about 200 ml, does not differ in those patients with gastrointestinal diseases accompanied by obvious symptoms (e.g., inflammatory bowel disease or IBD) from those whose symptoms are not externally validated (e.g., irritable bowel syndrome or IBS).7 Research has shown that in people who  complain of abdominal pain, and sometimes have an increased waist circumference, when objectively measured, are shown to have only about 28-118% (about 2 to 8 ounces) more gas in their intestines.3 The researchers concluded that the amount of just 1.9 to 8 oz. more gas wasn’t enough to create the problem of bloating but that the distribution of the gas was cause of the problem.3

Theories on the causes of bloating include:3

  • Lack of abdominal tone—muscles are not being contracted (poor posture)
  • Tension (intestines are not relaxed)
  • Sensations, or mechanical functions, of the intestines are inappropriate (neuronal or muscular dysfunction)
  • Changes in normal intestinal motility and transit times (either increased or decreased)
  • Dysbiosis or alterations in the gut microbiota
  • Changes to normal intestinal amounts of water content or electrolyte levels (either increased or decreased

Remind yourself of these practical lifestyle recommendations:3,8

  • Cook vegetables, instead of eating them raw, to avoid excessive internal gas production
  • Over the course of the day, eat smaller amounts of gas-promoting foods
  • Avoid excessive amounts of food, especially those with high amounts of fat7 and less than 30 g of a dietary fiber supplement like psyllium9 or type 4 resistant starch from potato starch10
  • Fully chew foods (do not gulp or swallow large amounts to avoid swallowing air)
  • Avoid carbonated drinks
  • In general, recommended dietary fiber intake is 25 g for women and 38 g for men (about 14 g of fiber for every 1,000 calories you eat)
  • Continue to eat fruits, vegetables, legumes, whole grains, and nuts to reduce the risk of developing chronic conditions
  • Strengthen your core by learning to “hold in” abdominal muscles and maintain good posture throughout the day
  • Engage in moderate exercise to assist in healthy intestinal motility
  • Reduce stress by being mindful and consider meditation or yoga to relax the intestine

For immediate relief of abdominal pain-related flatulence:

  • Try to avoid intentionally holding in the gas and use the restroom as needed
  • One popular recommendation for immediate relief includes lying on the ground and hugging your knees to your chest
  • Consider recommendations from your healthcare practitioner, who may suggest dietary changes, pharmaceutical solutions, psychiatric/psychological treatment, or biofeedback (for improving neuronal and muscular function) depending on the cause(s)
  • While multiple probiotics have been tested for symptoms such as bloating, abdominal pain, and flatulence, some have demonstrated no efficacy, and others have demonstrated some benefit9
  • Activated charcoal and simethicone are typical over-the-counter supplements that people use to decrease gas; however, not all studies seem to indicate that these consistently show a significant benefit3,12
  • For severe pain, especially associated with weight loss, heartburn, vomiting, see a healthcare practitioner

In summary, the common sense recommendations of “a balanced diet” and exercise to keep you healthy includes assistance in the healthy handling of intestinal gas. So if you have flatulence, don’t give up on the fiber—increase your exercise!

This content is not intended as a substitute for professional medical advice, diagnosis, or treatment. Individuals should always consult with their healthcare professional for advice on medical issues.


  1. Rowland I et al. Gut microbiota functions: metabolism of nutrients and other food components. Eur J Nutr. 2017;57(1):1–24.
  2. Nordqvist C. Everything you need to know about flatulence. Medical News Today. https://www.medicalnewstoday.com/articles/7622.php. Accessed April 22, 2019.
  3. Abraczinskas D. UpToDate® December 6, 2018. https://www.uptodate.com/contents/overview-of-intestinal-gas-and-bloating# Accessed
  4. Furne JK et al. Dig Dis Sci. 1996;41(8):1631-1635.
  5. Kirk E. Gastroenterology. 1949;12(5):782-794. 
  6. Tomlin J et al. Gut. 1991;32(6):665-669.
  7. Azpiroz F. Gut. 2005;54(7):893-895.
  8. Dahl WJ et al. Journal of the Academy of Nutrition and Dietetics. 2015;115(11):1861-1870. February 28, 2019.
  9. Gonlachanvit S. Gut. 2004;53(11):1577-1582.
  10. Dahl WJ et al. Journal of the Academy of Nutrition and Dietetics. 2012;112(9):A46.
  11. Hungin APS et al. Alimentary Pharmacology & Therapeutics. 2018;47(8):1054-1070. 12. Jain NK et al. Am J Gastroenterol. 1986;81(7):532-535


About Noelle Patno, PhD:

Noelle Patno, PhD, is the Nutritional Scientist for Digestive Health at Metagenics. After pursuing chemical engineering at Stanford and engineering at Abbott, she sought an education in preventive nutrition from a basic science perspective by pursuing her PhD in Molecular Metabolism and Nutrition from the University of Chicago. Her current role involves researching and developing probiotics, prebiotics and other nutritional solutions and programs for promoting digestive health and overall health.

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