Tooting your own horn
Q I've heard your diet can affect how often you pass gas and how it smells. What else causes foul-smelling flatulence? And how much farting is normal?
A Foul-smelling flatus is largely a function of what we eat and how it is processed by our body and microbiome. For instance, a 1971 study published in Gut measured that those on a bean-containing high-fibre diet produced gas at a rate nearly double that of those on a fibre-restricted diet — a mean of 49.4 millilitres per hour versus 26.7 ml/h, to be precise.
If you think you (or a dear friend) pass gas more frequently than everyone else, know that we do it 10 times a day on average — but up to 20 times a day would be in the range of normal.
Ninety-nine per cent of intestinal gas is made up of nitrogen, oxygen, hydrogen, carbon dioxide and methane. These gases are odourless; it's the one per cent that contains sulphur, such as hydrogen sulphide, that ruins it for everyone else. When the bacteria in our colons metabolize our food, they can produce those sulphur-containing gases.
If you need a simple solution in a pinch — an upcoming work conference or a date in cosy quarters with someone special — take bismuth subsalicylate (Pepto-bismol). Not only has it been shown to neutralize more than 95 per cent of sulphide gases in the gut and to reduce symptoms of flatulence, but it can also prevent traveller's diarrhea. There is some concern about salicylate toxicity if you use it regularly long term, but if you need it for a day or two to ease your social discomfort, by all means, take 524 milligrams by mouth four times a day beforehand.
WHAT FOODS CAN CAUSE EXCESS GAS?
Certain starches are not digested well by the human body and travel to the colon, where they are fermented and risk producing malodorous gas. About a third of U.S. adults cannot adequately absorb lactose, a disaccharide found in milk products.
Other culprits are foods in the raffinose family, including beans, cruciferous vegetables such as broccoli and brussels sprouts, onions, mushrooms and even garlic.
WHY DO SO MANY PEOPLE PASS GAS ON PLANES?
This behaviour is attributable to the laws of elementary physics. With increasing altitude, air pressure — including intestinal air pressure — falls. According to the ideal gas law, the volume of your intestinal gas will expand. Since a small muscle called the ileocecal valve prevents that gas from travelling backward from your colon into your small intestine, it has little choice but to move forward and outward.
CAN FLATULENCE BE A SIGN OF A HEALTH CONDITION?
Some may have observed that their noxious gas production skyrockets when they're constipated and need to have a bowel movement. Think about it: When you're constipated, your stool is just sitting there in your colon getting fermented into oblivion. The closer that stool is to the exit hatch, the more quickly the resulting gas will escape, much to the horror of your co-workers.
Besides constipation, if you have a disease that affects how well your small bowel absorbs nutrients — such as inflammatory bowel disease, pancreatic insufficiency or celiac disease — you'll also have increased gas because more of that partially digested food will land in your colon for your microbiome to feast upon.
WHAT I WANT MY PATIENTS TO KNOW
Most of the time when someone comes to me concerned about what they think is the worst flatulence in the world, when they actually spend a day counting how often it happens — we discover it's no more frequent than anyone else's.