Gulp: Adventures on the Alimentary Canal

Roach explores the complex science of saliva through her visit with researcher Erika Silletti, who studies this bodily fluid in her laboratory in the Netherlands. Roach discovers that humans produce two distinct types of saliva: stimulated saliva, which flows from the parotid glands when eating, and unstimulated saliva, the background flow that occurs constantly. The chapter reveals saliva’s critical protective functions, particularly its ability to neutralize acids from foods and drinks that would otherwise dissolve tooth enamel through demineralization.

Roach examines saliva’s digestive properties, noting that it contains amylase, an enzyme that breaks down starches into simple sugars. This discovery led her to investigate how commercial laundry and dishwashing detergents actually contain digestive enzymes similar to those found in human saliva, making these products essentially “digestive tracts in a box” (99). Art conservators also utilize saliva’s enzymatic properties to clean delicate paintings and gilded surfaces.

The chapter addresses common misconceptions about saliva production, citing scientific studies that contradict the popular belief that food smells trigger mouth watering. Research conducted at Harvard and King’s College London demonstrated that olfactory stimulation rarely increases salivation, challenging widespread assumptions about this bodily response.