Increased gassiness and bloating during air travel is a common phenomenon. This discomfort is a direct and predictable result of fundamental physical laws interacting with the human digestive system. The core issue lies in how the body handles the gas already present in the stomach and intestines under conditions of reduced atmospheric pressure. As the aircraft climbs, the gas inside the body changes volume significantly.
The Physics Behind Gas Expansion in Flight
The scientific explanation for in-flight gas discomfort relates to a principle of physics: the volume of a gas is inversely proportional to the pressure exerted on it. As the surrounding pressure decreases, the volume of the gas increases. Commercial aircraft cruise at altitudes where the atmospheric pressure is much lower than at sea level, even though the cabin is artificially pressurized.
Cabin pressure is generally maintained to be the equivalent of an altitude between 6,000 and 8,000 feet above sea level. This pressure drop is substantial enough to cause trapped gas in the gastrointestinal tract to expand significantly. Studies show that the volume of gas in the gut can increase by as much as 30% when ascending to a simulated altitude of 8,000 feet.
This expansion puts stress on the walls of the stomach and intestines, leading to feelings of tightness, bloating, and the necessity to pass gas. The greater the volume of gas present before takeoff, the more pronounced the discomfort will be at cruising altitude. During descent, the inverse effect occurs as the gas volume contracts when pressure increases.
Sources of Gastrointestinal Gas During Air Travel
The gas that expands during a flight comes from two main sources: swallowed air and gas produced internally by gut bacteria. The act of swallowing air, or aerophagia, contributes to gas buildup in the stomach and upper digestive tract. This is exacerbated by behaviors like chewing gum, drinking through a straw, or consuming carbonated beverages, which introduce extra air into the system.
The second source is gas generated by the fermentation of undigested food in the large intestine. Certain types of carbohydrates and fibers are not fully broken down by human enzymes. Bacteria in the colon feast on these leftovers, producing gases such as hydrogen, carbon dioxide, and methane as byproducts.
Foods containing high amounts of fermentable carbohydrates, known as high-FODMAP foods, are potent gas producers. Examples include onions, garlic, apples, pears, and dairy products containing lactose, especially for those who are lactose intolerant. The gas generated from these sources is readily available to expand once the aircraft reaches cruising altitude.
Practical Strategies for Reducing In-Flight Discomfort
Managing in-flight gassiness begins with mindful dietary adjustments in the 24 hours leading up to the flight. Avoiding highly fermentable foods, such as beans, lentils, broccoli, cauliflower, and garlic, can reduce the internal gas load. Limiting the intake of foods high in sugar alcohols or artificial sweeteners, which are often poorly digested, can also help minimize bacterial gas production.
In-flight behavior also plays a role in minimizing swallowed air. Passengers should avoid carbonated drinks, including soda and sparkling water, as the bubbles introduce trapped gas directly into the stomach. Chewing gum should also be avoided because it prompts excessive air swallowing.
Incorporating gentle movement during the flight can assist the body in naturally passing accumulated gas. Walking the aisle periodically or performing light stretches can stimulate intestinal motility. Over-the-counter aids, such as products containing simethicone, may also be helpful, as this compound breaks down large gas bubbles into smaller ones that are easier to pass.