But Why: How Does Food Turn into Poop?

Podcast Information:

• Title: But Why: A Podcast for Curious Kids
• Host: Jane Lindholm, Vermont Public
• Description: A child-led curiosity podcast where kids ask questions about the world, and experts provide answers.
• Episode: How Does Food Turn into Poop?
• Release Date: November 15, 2024

Introduction

In the But Why episode titled "How Does Food Turn into Poop?", host Jane Lindholm explores the intricate journey of food through the human body, addressing common and quirky questions posed by curious children. The episode features renowned science writer Mary Roach as the guest expert, who delves into the science of digestion, the role of bacteria, and even the complexities of waste elimination in space.

Understanding the Digestive Process

Mary Roach begins by outlining the fundamental stages of digestion, simplifying the complex biological processes into digestible (pun intended) explanations suitable for young listeners.

• Chewing and Swallowing:

  [02:57] Mary Roach: "First thing you have to do is chew it up so it's kind of a mushy thing that you can swallow... then you form it into a swallowable thing called a bolus."

• Stomach Breakdown:

  [03:54] Mary describes how the stomach further deconstructs food into a "liquidy porridge" before it moves into the small intestine for nutrient absorption.

• Nutrient Absorption and Waste Formation:

  [04:32] Jane Lindholm: "Most of the nutrients you get from your food are absorbed into your body in the small intestine."

  [04:53] Mary explains, "A lot of water gets taken out... what you end up with is stuff that your body can't use... turns into poop."

Detailed Q&A with Curious Kids

The heart of the episode lies in the engaging Q&A segment where Mary Roach addresses various questions from children, each shedding light on different aspects of digestion and waste.

1. How Does Food Turn into Poop?

• Question by Matteo (8, St. Paul):

  [03:37] "How does your food turn into your poop?"

• Mary's Explanation: Mary outlines the journey from chewing to nutrient absorption, emphasizing the role of the small intestine and water absorption in forming feces.

  [05:47] "A lot of absorption happens there and more breaking down, and then what you end up with, it's like the stuff that your body can't use, lots of fiber and stuff that will turn into poop."

2. How Do People Pee and Poop?

• Question by Spencer (5.5, North Vancouver):

  [05:47] "How do people pee and poop?"

• Mary's Response: She differentiates between the urinary and digestive systems, explaining that "the kidneys and the bladder handle liquids, and the intestine is what's making the poo."

  [06:00] "Well, there are different systems. I mean, you've got the kidneys and the bladder... the intestine is what's making the poo."

3. Why is Our Poop Brown?

• Questions by Rhode (3, Lincoln, Massachusetts) and Bowsey (7, Vietnam):

  [06:14] "Why is our poop brown?"

• Mary's Clarification: She attributes the brown color to bile and bilirubin, combining with fiber and fats to produce the typical hue.

  [06:35] "That has to do with these substances that are secreted called bile and bilirubin."

4. Why Do Poo and Farts Smell?

• Question by Sam (7, Dublin, Ireland):

  [07:38] "Why do poo smell so bad?"

• Mary's Insight: She explains the chemical breakdown of food leading to smelly compounds like hydrogen sulfide, which act as evolutionary signals to avoid harmful substances.

  [07:38] "Hydrogen sulfide, smelly substance... maybe we've evolved to hate that smell because it can be dangerous stuff."

• Additional Question by Eric (9, Bainbridge, Washington):

  [19:20] "Why do farts stink?"

• Mary's Explanation: The smell from farts is due to certain foods breaking down into odorous gases during digestion.

  [19:29] "Some of the things we eat... a gas is created. Some of those gases, like hydrogen sulfide, are really stinky."

5. Why Do Flies Like Poop?

• Question by an unnamed child (5, Bronson, Michigan):

  [09:28] "Why do flies like poop?"

• Mary's Answer: Flies are attracted to poop not for eating but for breeding grounds, offering warmth, moisture, and nutrients for larvae.

  [09:45] "They're not eating it so much as they're setting up housekeeping... poop is something for them to eat."

6. How Many Germs Are in One Ounce of Poop?

• Question by Henry (7, Brooklyn):

  [10:29] "How many germs are in one ounce of poo?"

• Mary's Response: Mary estimates "trillions" of bacteria, a figure later clarified by Jane Lindholm using CDC data.

  [10:37] "Oh, gosh. I'm gonna say trillions... just a crazy, crazy amount of bacteria."

  [11:36] Jane Lindholm: "The CDC says each gram of poop has 1 trillion germs. So one ounce of poop has about 28 grams, trillion or so germs."

7. How Does Fiber Make You Poop?

• Questions by Anya (4, Lancaster, Pennsylvania) and Liam (5, Princeton, Texas):

  [13:07] "How does fiber make you poop?"

• Mary's Explanation: Fiber isn't fully broken down by gut bacteria, aiding in forming bulkier, easier-to-pass stool.

  [13:27] "The bacteria in your guts don't break [fiber] down all the way... they just pass right on through."

8. Why Do We Have to Poop?

• Question by Titi (5, Los Angeles, California):

  [14:17] "Why do we have to go to the bathroom?"

• Mary's Insight: Pooping prevents the gut from becoming overly stretched and bursting, averting bacterial infections.

  [14:28] "Because otherwise we'd explode... you don't want your gut to burst."

9. How Do Astronauts Poop in Space?

• Question by Georgia (5, Cotton on Horton, New York):

  [15:21] "How do astronauts go poop in space?"

• Mary's Detailed Account: Mary recounts the evolution of space toilets from simple bags with adhesive rings to complex airflow systems on the International Space Station, highlighting challenges like "fecal decapitation."

  [16:01] "It's a very complicated machine, the space toilet."

10. Why Do People Fart and Why Are They Noisy?

• Questions by Finn (7, San Diego) and Frankie (5, Bangara Heights, New Zealand):

  [22:38] "Why do people fart?"

• Mary's Response: Farting serves as a vital release of excess gas to prevent gut rupture, comparing it to an "emergency release valve."

  [22:59] "It's a life-saving maneuver to fart because if you didn't fart, the gas would get to the point where your gut would burst."

• Additional Discussion on Noises: Mary explains that the sound of farts varies based on the force and dispersion of gas, with quieter farts often being "silent but deadly."

  [21:15] "One expert felt that when you blow out with gusto, the gas disperses more, so there's not as much smell in any one place."

The Role of Bacteria in Digestion

Mary Roach emphasizes the symbiotic relationship between humans and gut bacteria, vital for breaking down food into usable nutrients.

[12:20] "If you didn't have them, you would not be able to get nutrition from your food."

She describes the gut as a "bacteria farm," where trillions of bacteria work tirelessly to digest food, outnumbering human cells in the body.

[11:42] "We are just big bacteria farms, just production, production companies going about its business in there."

The Importance of Fiber

Jane Lindholm elaborates on fiber's role in digestive health, explaining how it aids in maintaining regular bowel movements and preventing conditions like constipation and diarrhea.

[14:01] "Fiber helps your body in a number of ways. It becomes food for that good bacteria we talked about earlier, and it can help make your poop easier to get out of your body."

Pooping in Space: A Closer Look

Astronauts' unique challenges with waste elimination illustrate the complexities of human biology in microgravity environments. Mary details early methods and the advancements leading to the current airflow-based systems, which, despite improvements, still face issues like poop floating uncontrollably if not managed correctly.

[16:02] "They're very complicated machines, the space toilets."

Farting: More Than Just a Noise

The episode transitions to discuss farts, addressing common misconceptions and the physiological necessity behind them. Mary clarifies that while farts are often a source of humor or embarrassment, they play a crucial role in maintaining digestive health.

[22:38] "Farting keeps you alive. It's a life-saving maneuver."

She also touches on the social aspects, advising listeners to be considerate about when and where they discuss or produce fart sounds.

Conclusion

But Why successfully demystifies the seemingly taboo topic of digestion and waste, transforming it into an engaging and informative discussion tailored for young minds. With Mary Roach's expertise, listeners gain a comprehensive understanding of the digestive system, the essential role of bacteria, and the complexities of waste management both on Earth and in space.

Jane Lindholm wraps up the episode by reinforcing the importance of respectful conversation around such topics while encouraging continued curiosity.

[25:13] Jane Lindholm: "We've been throwing the rules of polite conversation out the window in this episode, but it's all in service of science and understanding our bodies."

Key Takeaways

• Digestive Stages: From chewing to nutrient absorption, each step is crucial in transforming food into usable energy and waste.
• Bacteria's Role: Gut bacteria are essential for breaking down food, aiding in nutrient absorption, and maintaining overall health.
• Fiber's Benefits: Dietary fiber facilitates smoother digestion and regular bowel movements by acting as food for beneficial bacteria and adding bulk to stool.
• Waste Management: Pooping and farting are vital bodily functions that prevent the buildup of harmful substances and gases.
• Space Challenges: Managing waste in space poses unique engineering and biological challenges, highlighting the complexities of human biology beyond Earth.

Notable Quotes

• [02:57] Mary Roach: "I go around and I sit down with people who know a lot and I pick their brains and I ask a lot of questions."
• [04:32] Jane Lindholm: "Most of the nutrients you get from your food are absorbed into your body in the small intestine."
• [07:38] Mary Roach: "We may have evolved to hate that smell because it can be dangerous stuff."
• [10:37] Jane Lindholm: "The CDC says each gram of poop has 1 trillion germs. So one ounce of poop has about 28 grams, trillion or so germs."
• [22:38] Mary Roach: "Farting keeps you alive. It's a life-saving maneuver."

Final Thoughts

This episode of But Why not only answers children’s burning questions about digestion and waste but also emphasizes the importance of these processes in maintaining health. By addressing topics often considered "gross" with scientific accuracy and humor, the podcast fosters a healthy curiosity and encourages open discussions about the human body.

Remember: If you have more curious questions, have an adult record you asking them and send the recording to questions@butwhykids.org. Stay curious!