Does your methane smell?
People always think methane is smelly. I do research in gastroenterology and one of the gases we test in breath samples is methane, and because people associate methane with fart odour I get strange looks and jokes. People I’m going to test are embarrassed by the idea of me knowing they produce methane.
To clear this up for once and for all:
Methane is an odourless gas. No smell. At all.
Why do we measure methane in breath samples? The quick and dirty run-down: Breath hydrogen tests are a non-invasive test used to diagnose gastrointestinal problems like lactose intolerance. When a sugar like lactose is not fully absorbed from the small intestine, intestinal bacteria will metabolise the lactose and produce the gas hydrogen (and possibly methane). The hydrogen/methane diffuses into the blood stream and is expired from the lungs, and therefore we can measure it in breath samples.
Methane
Yes, hydrogen and methane are produced in your large intestine and they do contribute to flatulence, but they don’t smell. So please, please, no more smelly methane comments. The most recent suggestion was that a really good angle for a media release about my work would be: do you know if methane is giving you bad breath? Enough!
So what’s the smell then?
Since I’m trying to convince you that methane and hydrogen don’t smell, I should give an explanation for what does cause the stink. While I emphatically don’t work with flatulence, inevitably someone has done the research and sampled farts to find out why they smell. Would you want to volunteer for this study:
Flatus was quantitatively collected via rectal tube from 16 healthy subjects who ingested pinto beans and lactulose to enhance flatus output. The concentrations of sulphur-containing gases in each passage were correlated with odour intensity assessed by two judges.
First, for the scientific take on whether men or women produce the worst farts: women’s farts are smellier, but men’s farts are bigger. How big is an average fart? Women 88 ml. Men 119 ml.
The stench is caused by sulfur-containing gases produced by bacteria in our intestines. The amount of sulfur gases in the flatulence strongly correlates with the “odour intensity”. The most important sulfur component is probably hydrogen sulphide, followed by methanethiol.
My search on Pubmed for flatulence also turned up testing of fart-proof undies. It’s amazing what’s on Pubmed – 99% of the time it’s dead boring, and then there’s something bizarre like this. And this wasn’t in some low-rank dodgy journal either – I wish I was published in Am J Gastro.
In the name of blogging I bravely go Googling: the search produced lots pictures of hideous airtight undies with fart filters sewn in
Since you’re all dying to find out whether you’ve got the most effective anti-fart undies, or if you should be dashing out to the shop for a different sort: the only one that’s really effective is underwear made from activated carbon fabric. Apparently another moderately effective product is activated carbon pads that are inserted in your undies, while fart-proof cushions you sit on aren’t effective at all.
If you already knew these products existed, I wouldn’t own up to it if I was you. Just quietly get a refund on your fart cushion.
Now that I’ve had to go and look up things I’ve never wanted to know about, I’ve run out of time. So you can find out how methane can make your intestines explode next post.
Beck
12/05/2011
Thanks for a good giggle on an otherwise dull Thursday afternoon!
Can you imagine being one of the two judges assessing ‘odour intensity’? Awful!!