Digestive symptoms

Flatulence

Also called: wind, gas, farting

Flatulence is gas passed from the bowel. The healthy adult passes wind 10 to 20 times a day, totalling about 0.5 to 2 litres. Most gas is odourless (nitrogen, carbon dioxide, hydrogen). The smelly portion comes from sulphur compounds bacteria produce when fermenting protein and certain plants. Reducing total volume usually means reducing fermentable carbs; reducing smell usually means reducing sulphur-containing protein and cruciferous vegetables.

What's normal

  • 10 to 20 times a day, even in healthy adults.
  • 0.5 to 2 litres of gas total per day.
  • More on high-fibre days. Less on low-fibre days.
  • More in the evening as gas accumulates through the day.
  • Often more during the luteal phase in women.
  • Smelly farts a few times a week is normal. Foul, persistent stink is not.

Where the gas comes from

  • Air swallowed during eating, drinking and chewing gum.
  • Carbon dioxide produced when stomach acid neutralises bicarbonate from food.
  • Hydrogen and methane from bacterial fermentation of fibre and undigested carbs.
  • Sulphur compounds (the smell) from bacterial fermentation of sulphur-containing proteins (eggs, meat, cheese) and cruciferous vegetables (broccoli, cabbage, cauliflower).

Why some farts smell so bad

Hydrogen sulphide (the rotten egg smell), methanethiol and dimethyl sulphide are the main culprits. They are produced when bacteria ferment sulphur-containing amino acids (cysteine, methionine, high in meat, eggs, dairy) or sulphur-rich vegetables (broccoli, cabbage, brussels sprouts, cauliflower, garlic, onion). Reducing total intake of these makes wind less smelly without changing the volume.

What reduces total volume

  1. Slow ramp on fibre intake, fast increases produce dramatic gas spikes that settle in 2-3 weeks.
  2. Soak beans overnight, drain, cook in fresh water. Removes 30-40 percent of FODMAP gas-producing carbs.
  3. Beano enzyme (alpha-galactosidase) before legume meals.
  4. Eat slowly, chew thoroughly, don't talk while eating. Reduces swallowed air.
  5. Avoid carbonated drinks with high-FODMAP meals.
  6. Walk after meals. Helps gas move through, reduces evening accumulation.
  7. If volume is severe and persistent: consider FODMAP elimination under a dietitian to find specific triggers.

What reduces smell

  • Reduce sulphur-rich foods on important days: eggs, meat, dairy, broccoli, cabbage, garlic, onion.
  • Bismuth subsalicylate (Pepto-Bismol) chemically binds sulphur compounds and reduces smell. Useful for known social-stakes occasions; not for daily long-term use.
  • Activated charcoal underwear (yes, real product) absorbs sulphur smell.
  • Drink water, concentrated stools and slow transit produce more sulphur breakdown.

When excessive wind is worth checking

  • More than 25 times a day, persistently.
  • Sudden increase from your baseline lasting weeks.
  • Combined with weight loss, blood in stool, or pain.
  • Combined with malabsorption symptoms (greasy floating stools).
  • Possible: SIBO, lactose intolerance, fructose malabsorption, exocrine pancreatic insufficiency.

Common questions

Why does my fart smell different on holiday?
Different food, different microbiome activity. New foods feed different bacteria; their byproducts smell different. Usually resolves within a week of returning to normal eating.
Are silent farts always smelly?
Often yes. Quieter farts have higher concentrations of sulphur compounds because the gas is denser and more slowly released. Fast loud farts are usually mostly air and CO2, less smelly.
Does activated charcoal help?
Charcoal underwear (Shreddies, Flat-D) absorbs sulphur compounds in clothing, works. Oral activated charcoal capsules: weak evidence, can interfere with medication absorption, not generally recommended for routine wind.
Is daily wind a sign of bad gut health?
No, the opposite often. Daily moderate wind means your gut bacteria are actively fermenting fibre and producing short-chain fatty acids. Very low wind can actually mean low microbiome activity. The thing to track is sudden change from your baseline, not absolute volume.

Sources