Brains On! Science podcast for kids · Brains On Universe

Why doesn’t stomach acid burn right through us?

February 10, 2026·29 min·2 clips

Stomach acid can dissolve metal, so why doesn't it burn a hole right through our bodies?

This episode of Brains On! explores why powerful stomach acid doesn't burn through our bodies, featuring host Molly Bloom and kid co-host Wesley from Columbia, Missouri. They investigate the stomach's defenses with help from producer Mark and his fictional "organophone" device for talking to body parts. The episode also includes a game segment about unusual animal digestion. Stomach acid, or gastric juice, contains hydrochloric acid and digestive enzymes that can dissolve metals like zinc and break down food. The human body produces three to four liters of this acid daily, equivalent to two large soda bottles. A key defense is a mucus layer secreted by glands in the stomach lining, which acts as a protective shield. This mucus contains bicarbonate, an alkaline substance similar to baking soda that neutralizes the acid. The stomach lining also constantly sheds and regenerates cells, replacing its entire lining every couple of days to prevent damage. The episode references historical experiments by Dr. William Beaumont on a patient named Alexis St. Martin, who had a permanent stomach opening from a gunshot wound in 1822. Beaumont's observations, though ethically questionable by modern standards, advanced the understanding of digestion. In the "Digestion Suggestion" game, listeners learn cows regurgitate and re-chew their food, ostriches swallow rocks to grind food in their gizzards, and vultures have extremely strong stomach acid to handle rotting meat. The mystery sound, submitted by Owen Smith, is revealed to be someone flicking the tab on a soda can until it pops off. A surprising insight is that stomach acid production can begin just from thinking about food, like seeing a delicious plate of tacos. The stomach describes its mucus as "liquid gold" and bicarbonate as the "bicarbo-bomb" for neutralizing acid. The historical account reveals Beaumont would tie food to a string, insert it into St. Martin's stomach, and observe digestion, often causing discomfort. The tone is playful and educational, using humor, character voices, and interactive segments like the game show and mystery sound. The style is highly conversational, with imaginative elements like a talking stomach and musical jingles to explain biological concepts. Young science enthusiasts and curious kids who enjoy fun, interactive explanations of bodily functions would love this episode. Listeners interested in historical medical practices might find the segment on William Beaumont particularly engaging. Those who prefer strictly serious, documentary-style science content might find the playful tone and fictional elements less appealing.

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