How Scientists Count Farts

Predict

A fart is gas that leaves your body through your bottom. For many years, doctors said healthy people fart about 10 to 14 times a day. Do you think healthy people fart more than 14 times a day?

Circle one. Yes / No

Why?

Watch

1. I’m farting for science!youtube.com/shorts/8OqwMEsxD38

Word of the day

Flatus (FLAY-tus). Gas made in the digestive tract and passed out through the anus.

• Inflation, a steady rise in prices, comes from Latin inflāre, “to blow on or into, puff out,” with the same flā- root.
• To conflate two things is to fuse them into one. Conflate comes from Latin conflāre, from con- and flāre, “to blow.”

Bonus word. Microbiome (MY-kroh-BY-ohm) is the community of microorganisms, together with their genetic material, living in or on a body or in an environment. The word joins Greek mīkrós, “small,” and bíos, “life,” with the ending -ome, as in biome.

Questions

1. A 1979 paper by gastroenterologist Michael Levitt listed the normal number of farts as 14, plus or minus 6, a day. In a 1996 study, 25 healthy people kept count for a week and averaged 10 a day. The Smart Underwear study, which used a hydrogen sensor, found an average of 32 a day, with daily totals from 4 to 59. Why could counts people keep for themselves come out lower than a sensor’s count? Give two reasons.

   Hint. Think about sleep, and about farts too small or quiet to notice.

2. In a 1991 study, 10 healthy volunteers wore a flexible tube, placed in the rectum, that collected their gas for 24 hours. When 6 of the volunteers drank a liquid diet with no fiber for 48 hours, the hydrogen in their gas nearly disappeared. What does the drop in hydrogen tell you about where the hydrogen in flatus comes from?

   Hint. The small intestine can’t digest some fiber. Which living things in the large intestine could use fiber that reaches them?

3. In the same 1991 study, the volunteers also wrote down each time they noticed passing gas, a median of 8 times. The number of times a volunteer noticed passing gas did not line up with how much gas the tube collected. What does the 1991 study suggest about using people’s own notes to measure gas?

   Hint. When notes and a measurement disagree, which one would you trust to measure gas?

4. The Smart Underwear detects farts by the hydrogen gas in them. In the video, Raven asks, “What counts as a fart?” Picture a careful counter wearing a sensor that works correctly. How could the person’s count and the Smart Underwear’s count still disagree?

   Hint. Some farts carry little hydrogen, and some farts are too small to feel.

Claim, evidence, reasoning

Going further: Zen Digesters

1. The Smart Underwear team is recruiting people it calls Zen Digesters. Zen Digesters eat 25 to 38 grams of fiber a day yet pass little gas. Gut bacteria break down fiber without oxygen. This breakdown, called fermentation, releases gases such as hydrogen. Some gut microbes use up hydrogen and turn the hydrogen into other products, such as methane. How could a Zen Digester eat plenty of fiber and still make so little gas? What measurement would test your explanation?

   Hint. Think about which microbes live in a Zen Digester’s gut. The team plans to collect stool samples from Zen Digesters.

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