Altitude Flatulence: Why You Fart More on Planes and in the Mountains
As altitude increases, air pressure drops — and intestinal gas expands. What physicists know as Boyle's Law, millions of passengers experience firsthand every day: at cruising altitude of 30,000 feet, intestinal gas is about 30% larger than at ground level. Mountain climbers know the phenomenon too. The science behind it is precise, and the strategies for relief are surprisingly simple.
Boyle's Law in Your Belly
The physical principle behind altitude flatulence is straightforward: at constant temperature, P × V = constant — so when pressure drops, volume increases. On an airplane, the cabin is pressurized to about 75% of ground-level pressure, equivalent to the atmospheric pressure at roughly 8,000 feet (2,400 meters). This means the gas inside your intestines expands by about 25 to 30%. If you have 200 ml of gas in your gut on the ground, you'll have 250 to 260 ml by the time you reach cruising altitude. That may sound like little, but in the confined space of the intestine, it's quite noticeable. The same applies to mountaineers: at 10,000 feet (3,000 meters), air pressure is only about 70% of sea level. At the summit of Everest (29,032 feet / 8,848 meters), pressure drops to about 33% — theoretically tripling the volume of intestinal gas, which is one reason extreme climbers suffer significant bloating.
Aircraft Cabins: Pressure, Digestion, and In-Flight Turbulence
On long-haul flights, passengers sit for hours in a slightly reduced-pressure environment with limited ability to move around. This prevents the natural passage of intestinal gas — walking upright is one of the most effective ways to promote bowel transit. At the same time, extremely dry cabin air (relative humidity often below 20%) means staying hydrated is important. Dehydration slows gut transit and worsens bloating. Studies confirm: passengers on planes actually pass gas more frequently than on the ground. A widely cited New Zealand study (Dr. Jacob Rosenberg, 2013) investigated this seriously and concluded that the social pressure not to pass gas in the cabin causes significant discomfort. Rosenberg's recommendation: 'Let it go.' Pilots seated in pressurized cockpits are affected too — aviation medicine considers flatulence a potentially distracting factor.
Altitude Sickness and Intestinal Gas: The Connection
Ascending quickly to above 8,200 feet (2,500 meters) without adequate acclimatization can trigger acute mountain sickness. Alongside headaches, nausea, and sleep disturbances, many people report strong bloating and digestive issues. The connection is multilayered: first, intestinal gas physically expands. Second, with oxygen deprivation (hypoxia), gut function changes — the bowel lining receives less blood flow and motility is altered. Third, mountaineers often drink less at altitude (loss of appetite is a classic symptom), which promotes constipation and bloating. Expedition doctors therefore recommend for high-altitude treks: acclimatize gradually, drink plenty, and eat a low-gas diet during the first few days at new elevation.
Dietary Strategies for Frequent Flyers and Mountaineers
The good news: altitude bloating is very manageable through diet. Before long-haul flights, nutrition experts recommend avoiding FODMAP-rich foods the day before and on travel day: legumes (beans, lentils), onions, cabbage, carbonated drinks, and chewing gum (due to swallowed air). Drinking carbonated beverages on a plane is particularly counterproductive — the gas in the drinks adds to already-expanding intestinal gas. For mountaineers: calorie-dense, easily digestible food in the first days at new elevation. Potatoes, rice, plain pasta — easy to digest, low fermentability. Activated charcoal tablets are popular among some air travelers, but their specific effectiveness against altitude bloating is not clearly established.
Did you know?
- On a plane, intestinal gas expands by 25–30% — cabin pressure is equivalent to an altitude of about 8,000 feet (2,400 meters).
- A New Zealand study from 2013 officially recommended that pilots and passengers pass gas on planes rather than hold it in.
- At the summit of Mount Everest, air pressure is only 33% of sea level — intestinal gas would theoretically triple in volume.
- Drinking carbonated beverages on a plane worsens altitude bloating considerably, as the gas also expands.
Fun Fact
NASA took intestinal gas in space very seriously — and aircraft cabins are in some ways the training ground for that extreme scenario. In the early days of spaceflight, it was known that hydrogen in intestinal gas could theoretically pose an explosion risk at certain concentrations. NASA nutritionists in the 1960s therefore developed special low-gas diets for astronauts — beans were definitively not on the menu.
Sources
- Rosenberg, J. & Pasternak, I. (2013). Flatulence on airplanes: just let it go. New Zealand Medical Journal.
- Bärtsch, P. & Swenson, E.R. (2013). Acute High-Altitude Illnesses. New England Journal of Medicine.
- Levitt, M.D. (1971). Volume and composition of human intestinal gas. New England Journal of Medicine.