Human Digestion Simulator
Build a meal, feed it through the digestive tract, and watch real enzymes break carbohydrates, protein and fat down while a graph tracks nutrient absorption over time.
Build a meal, press Feed, and follow the bolus through the mouth, esophagus, stomach, small intestine and large intestine while enzymes break down carbs, protein and fat.
About the Human Digestion Simulator
Free human digestion simulator. Build a meal, feed it through the digestive tract, and watch real enzymes break carbohydrates, protein and fat down while a graph tracks nutrient absorption over time. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for biology, the human digestion simulator runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Build a meal, feed it through the digestive tract, and watch real enzymes break carbohydrates, protein and fat down while a graph tracks nutrient absorption over time. Use it to explore biology ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Human Digestion Simulator
- Use the controls to change Meal size, Carbohydrate share, Protein share, Fat share, Transit speed. The simulation reacts instantly.
- Press "Feed the meal", "Reset to defaults", "Check absorption", "Check fat absorption" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Feed a high-fat meal and watch how long fat digestion takes compared to carbohydrate.
- Slow down transit speed and see how much more gets absorbed before the small intestine ends.
- Try the challenge: get over 90% of the carbohydrate absorbed before the meal reaches the large intestine.
Key ideas you can learn
- Carbohydrate digestion starts with salivary amylase in the mouth and finishes with pancreatic amylase in the small intestine, ending as glucose.
- Protein digestion starts with pepsin and stomach acid, then pancreatic proteases in the small intestine, ending as amino acids.
- Fat is emulsified by bile and broken down by lipase in the small intestine into fatty acids and glycerol.
- Almost all nutrient absorption happens in the small intestine; the large intestine mainly absorbs water.
Where this is used in the real world
Nutritionists design meals around exactly this timeline, and medical conditions like lactose intolerance or pancreatic insufficiency are explained by a missing step in this same pathway.
Who is this simulation for?
Biology students and teachers who want to explore living systems, populations and genetics interactively and safely.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
Why does protein digestion start in the stomach but carbohydrate digestion pauses there?
Stomach acid activates pepsin for protein digestion but also stops salivary amylase from working, so carbohydrate digestion resumes only once food reaches the small intestine.
What is bile's role in fat digestion?
Bile emulsifies fat into tiny droplets, giving lipase far more surface area to break it down efficiently.
Is the Human Digestion Simulator free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Human Digestion Simulator work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.