Quick answer: Passing wind is a normal by-product of gut bacteria fermenting fibre and other carbohydrates; most healthy adults pass gas around 10 to 20 times a day. Excess or very smelly gas is commonly associated with fermentable foods (beans, onions, some fruit and sweeteners), swallowed air, a change in fibre intake, lactose or fructose malabsorption, constipation and IBS. Strong odour mainly comes from sulphur gases, which tend to rise with protein- and sulphur-rich meals. Gas on its own is rarely serious, but gas with weight loss, blood in the stool, persistent diarrhoea or a new change in bowel habit should be checked by your doctor.
Gas is one of the most common things people mention in a first session, often with some embarrassment. It is also one of the most misunderstood. More gas usually means your gut bacteria are being fed, which is not a bad thing in itself. The question is whether the amount, the smell or the discomfort fits with what you eat, or whether something else is going on. If gas comes with a swollen tummy, you may also find why you feel bloated after eating helpful.
How much gas is normal?
In a classic study of healthy volunteers, people passed wind on average around 10 times a day, with a normal range up to about 20, and total volume rose clearly on a high-fibre diet. Frequency varies with what you eat, how much air you swallow and your own microbiome. So there is no single "right" number: a sudden or sustained change from your usual pattern matters more than the count.
What causes excessive gas?
Most intestinal gas comes from two places: air you swallow and fermentation by bacteria in the large bowel. Common contributors include:
- Fermentable carbohydrates (FODMAPs) such as beans and lentils, onion, garlic, wheat, apples, pears and sugar alcohols like sorbitol and xylitol.
- A quick jump in fibre, for example a new high-fibre or "fibremaxxing" routine, before the gut has adapted.
- Lactose or fructose malabsorption, where sugars that are not absorbed reach the colon and are fermented.
- Constipation, which keeps stool in the colon for longer and gives bacteria more time to ferment.
- IBS, where the gut is often more sensitive to normal amounts of gas.
- Swallowed air from eating quickly, chewing gum, fizzy drinks or talking while eating.
Why does my gas smell so bad?
Most gas (hydrogen, carbon dioxide, methane) has no smell. Odour comes mainly from small amounts of sulphur gases, especially hydrogen sulphide. Research measuring flatus found these sulphur compounds correlated most closely with how offensive it smelled. Meals rich in animal protein, eggs, and sulphur-containing vegetables such as broccoli, cabbage and cauliflower can increase them. A very strong, persistent change in smell, especially with loose stools, is worth mentioning to your doctor.
When to see your doctor first
- Blood in or on the stool, or black stools
- Unintentional weight loss
- Persistent diarrhoea, or waking at night to open your bowels
- Severe or worsening abdominal pain, or a swollen, hard abdomen
- A new, persistent change in bowel habit after 50
- A family history of bowel cancer, coeliac disease or inflammatory bowel disease
- Anaemia or unexplained tiredness
Is excessive gas a sign of SIBO or a gut imbalance?
It can be part of the picture, but gas alone is not specific. In people who complain of flatulence, studies have found differences in the colonic microbiota and a stronger gas response to a fermentable diet. Bloating soon after meals, alternating bowel habits and other symptoms may point towards SIBO or IBS, which your doctor can investigate. Testing makes most sense when it would change what you do.
What can help reduce gas?
- Keep a short food and symptom diary for two weeks to spot patterns (see how to keep one).
- Increase fibre gradually and spread it across the day rather than cutting it out.
- Soak, rinse and cook pulses well; canned, rinsed lentils and chickpeas are often better tolerated.
- Eat slowly, and limit gum and fizzy drinks.
- Keep things moving: hydration, movement and regular meals support transit.
- Consider a short, guided low-FODMAP phase if symptoms are persistent, with planned reintroduction (who it suits).
In a controlled study, a low-flatulogenic diet reduced gas evacuation and digestive symptoms in people with flatulence. Enzymes such as alpha-galactosidase may reduce gas from beans in some people. Any supplement is optional, should be individualised and discussed with your doctor if you take medication.
Gas and bloating running your day?
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Book your free 15-minute call →Frequently asked questions
Is it normal to fart 30 times a day?
It is above the typical range, but it may still fit a high-fibre or bean-rich diet. If it is new, persistent or comes with pain or a change in bowel habit, it is worth looking into with your doctor.
Do probiotics reduce gas?
Results are mixed. Some people notice less gas, others feel worse at first. If you try one, choose a specific product for a set period and stop if symptoms increase.
Why do I have more gas at night?
Fermentation peaks a few hours after meals, so gas from lunch and dinner often builds up in the evening. Lying down and a slower gut overnight can also make it more noticeable.
Can stress cause gas?
Stress can change gut movement and sensitivity, and can make you swallow more air. Many people notice gas and bloating get worse during stressful periods.
Should I stop eating fibre if I have a lot of gas?
Usually not. Fibre feeds beneficial bacteria. It is often better to adjust the type and amount and increase it slowly.
References
- Tomlin J, Lowis C, Read NW. Investigation of normal flatus production in healthy volunteers. Gut. 1991. PubMed: PMID 1648028
- Suarez FL, Springfield J, Levitt MD. Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour. Gut. 1998. PubMed: PMID 9771412
- Manichanh C, Eck A, Varela E, et al. Anal gas evacuation and colonic microbiota in patients with flatulence: effect of diet. Gut. 2014. PubMed: PMID 23766444
- Azpiroz F, Hernandez C, Guyonnet D, et al. Effect of a low-flatulogenic diet in patients with flatulence and functional digestive symptoms. Neurogastroenterol Motil. 2014. PubMed: PMID 24548289
- Di Stefano M, Miceli E, Gotti S, et al. The effect of oral alpha-galactosidase on intestinal gas production and gas-related symptoms. Dig Dis Sci. 2007. PubMed: PMID 17151807
This article is for educational purposes and is not medical advice. Nutritional therapy does not replace medical care. Always work with your doctor for any persistent or new symptoms and before making changes to your care, medication or supplements.