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Digestion and absorption
Food processing begins in the mouth. The stomach mixes food with digestive juices; the small intestine continues digestion and absorbs most nutrients. The large intestine absorbs water and microbes process some undigested material. The liver and pancreas contribute digestive substances.
In-depth articles
All articles →What happens to a meal inside the body?
Follow food from the mouth through the small and large intestines, and learn how digestion and absorption differ.
→Where fluids come from: drinks, food and everyday hydration
Understand fluid sources, changing circumstances and practical observation, and why fluid needs vary.
→A map of related concepts; see the entries and sources for detail.
Open the interactive digestion explainer →
Reference entries
Mouth and stomach
Chewing breaks food into smaller pieces, and saliva begins processing starch. The stomach mixes food and digestive juices, which help digest protein.
Small intestine and absorption
The small intestine receives digestive substances from the pancreas, liver and intestine. Digested nutrients are absorbed through its wall; absorption mechanisms and extent differ by substance.
Large intestine and microbes
The large intestine absorbs water and forms stool. Gut microbes also process some undigested food components; ecological responses depend on food structure and individual context.
What is bioavailability?
It generally describes the fraction or extent of an ingested substance that becomes available for use. The label amount is not necessarily the amount absorbed or used, and study methods can differ.