Whether eating on the go or indulging in cravings, it’s important to understand how our bodies digest and process the foods we eat. This article provides a comprehensive overview of the digestion process from start to finish, highlighting key nutrition facts along the way.

As Amy finishes her burger, fries and chocolate shake from the fast food restaurant, her body immediately begins the digestive process. Ingestion is the first step, where the food enters the mouth and is broken down by chewing. Saliva containing the enzyme amylase is released, starting to break starches like the bun and fries into simpler sugars.

When Amy swallows her meal, it travels down the esophagus and into the stomach through peristalsis contractions. In the stomach, powerful contractions further grind and mix food with gastric juices containing hydrochloric acid and enzymes like pepsin. This acidic environment helps break proteins like those in the burger patty into smaller fragments.

After about 2 hours, the partially digested contents of Amy’s stomach empty into the small intestine as chyme. The small intestine is over 20 feet long and has numerous finger-like projections called villi that contain lacteals and blood vessels. Enzymes from the pancreas, liver, and intestinal cells themselves continue to break down carbohydrates, proteins and fats into their simplest building blocks called monosaccharides, amino acids and fatty acids respectively.

As nutrients are broken down into an absorbable form, they pass through the intestinal walls and into the bloodstream or lymphatic system. This is absorption – the point where the body gains useable vitamins, minerals and energy from the foods we eat. For example, broken down sugars from the shake provide fast energy while amino acids from the burger are used for muscle growth and repair.

Any remaining indigestible food matter like fiber passes from the small intestine into the large intestine where water is absorbed through osmosis, forming stool. Periodic muscular contractions called peristalsis move stool towards the rectum until it’s eliminated as waste.

Unfortunately for Amy, the lactose in her chocolate shake begins to cause issues. As someone with lactose intolerance, she lacks enough lactase to fully digest the milk sugar. Undigested lactose ferments in the colon by bacteria, producing gas and drawing water into the intestines. This leads to her typical symptoms of cramps and diarrhea.

By understanding the complex journey our food takes through the digestive system, we gain a new appreciation for the intricate processes that allow us to utilize nutrients for health, energy and survival. Making informed choices is key to supporting optimal digestion and overall wellness.


In summary, digestion is an intricate multi-step process that begins in the mouth and ends with the absorption of essential nutrients throughout the body. Making informed choices about our diets can support digestion and prevent issues. Understanding nutrition will help us fuel our bodies with the vitamins, minerals and macronutrients needed to thrive.


Q: What are the main stages of digestion?
A: The main stages are ingestion, stomach digestion, small intestinal digestion, absorption, and elimination.

Q: Why is proper nutrition important?
A: Proper nutrition supplies the body with vitamins, minerals, proteins and other nutrients necessary for growth, development, functioning and overall health and wellbeing.

Q: What causes lactose intolerance?
A: Lactose intolerance occurs when the body is unable to fully break down the sugars (lactose) in milk due to a deficiency in the enzyme lactase. This can lead to digestive issues like cramps and diarrhea.

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