Carbohydrate Digestion

Art & Research: Sarah Shardam

Further Reading Literature: Aisha Sadiqa

Mouth and stomach

After mechanical digestion (physically breaking the food into smaller pieces), food in the mouth then mixes with saliva, which is produced by several glands in the oral cavity, or the mouth. The enzyme salivary amylase breaks starch into smaller polysaccharides, or sugar subunits, and maltose (LibreTexts Medicine).

In high acidity, many enzymes are broken down and cease to function. The acidity in the stomach inactivates salivary amylase, so it no longer works when it arrives at the stomach.

Although there’s more mechanical digestion in the stomach, there’s little chcemical digestion of carbohydrates there.

Enzymatic breakdown in the intestines

Most carbohydrate digestion occurs in the small intestine thanks to a suite of enzymes. 

Pancreatic amylase is secreted from the pancreas into the small intestine, and like salivary amylase, it breaks down starches into smaller sugar pairs made up of glucose subunits.

Fructose and galactose are converted to glucose in the liver. Once absorbed carbohydrates pass through the liver, glucose in the main form of carbohydrate circulating in the bloodstream (MedlinePlus).

The large intestine

Any carbohydrates that aren’t digested in the small intestine - mainly cellulose fiber - pass into the large intestine. There are functions of the microbiota, or gut bacteria, that occur here as well as digestion that doesn’t occur in other parts of the digestive track (LibreTexts Medicine). The undigested material remaining then exits the body after the large intestine.

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