You probably know that carbohydrates are digested by your body in the small intestine, but did you know that they stop at the stomach? Food enters the stomach through the esophagus and travels to the small intestine through the digestive tract. Starch-free foods won’t get stuck in the small intestine, while starch-containing food can.

Intrinsic nerves

The brain contains two types of nerves: extrinsic and intrinsic. The extrinsic nerves are in the brain and spinal cord, and their function is to release chemicals, such as acetylcholine, that affect digestion. Acetylcholine stimulates the muscle, increasing its contraction and the force with which food moves through the digestive tract. Adrenaline, on the other hand, relaxes the stomach and intestine and reduces the blood flow to the digestive organs.

While carbohydrates are not further chemically broken down once they reach the stomach, they continue to be mechanically broken down. Amylase enzyme no longer functions in the acidic environment of the stomach. This is because the digestive juice produced by the pancreas is already digested in the small intestine. As food moves through the stomach, salivary amylase breaks the carbohydrates down to simple sugars, and these are then passed to the small intestine where they are further digested.

Acidic environment

The digestive process begins with the mouth, where the salivary enzyme amylase starts the breakdown of carbohydrates into maltose, a disaccharide. As the food travels through the mouth and the duodenum, it is broken down further by the pancreas. Amylase breaks down carbohydrates into dextrin and maltose. When the food reaches the small intestine, a mixture of partially digested food and gastric juice is released from the stomach. Movement of this mixture is controlled by muscle reflexes and hormones.

The stomach’s acidic environment prevents the digestive enzyme amylase from working properly. The amylase enzyme cannot function effectively in the acidic environment, so no further chemical breakdown occurs. However, mechanical breakdown continues, with strong peristaltic contractions mixing the carbohydrate particles into chyme. This process is known as the “switch-off” phase of the digestion process.

Leaching of solids to digestion medium

Once carbohydrates enter the stomach, they must overcome structural barriers to digestion. This requires the production of digestive enzymes and the secretion of bicarbonate, both of which are found in the stomach. In addition, digestion is triggered by the hormone ghrelin, which is released after a meal is swallowed. This is referred to as the cephalic phase of digestion.

The digestive process in the stomach involves the dissolving of starch in saliva, which reduces its viscosity and allows access to enzymes. Salivary a-amylase, a component of digestive enzymes, is responsible for starch breakdown. This process typically occurs within minutes or hours of food ingestion. Although the enzymes have limited effects on the rate at which carbohydrates are digested, they significantly influence the glucose level in the blood.

Mechanisms of carbohydrate digestion

After entering the mouth, carbohydrates travel to the stomach where they are chewed into smaller pieces. Amylase released from the pancreas then breaks down the chyme into dextrin and maltose. Then enzymes made in the small intestine called lactase and sucrase break down the sugars into simpler molecules that the body can use. This final step helps the body absorb nutrients from food.

Short chain sugars are digested into monosaccharides by the gut brush border disaccharidases. The rate at which the gut wall is traversed depends on the capacity of membrane-bound transporters to recognize these monosaccharides. During this process, the gut wall is passed rapidly, allowing glucose to reach the bloodstream. By the time the food reaches the small intestine, most of the sugars are gone.