How are lipids digested

Fat digestion

English: fat digestion

1 definition

As Fat digestion are the physiological processes that take place after the ingestion of fats with food for their digestion.

2 physiology

2.1 General

The digestion and absorption of fats depends largely on the chain length of the fatty acids. MCT (medium-chain triglycerides) are "processed" and absorbed much faster than LCT (long-chain triglycerides).

2.2 stomach

Fat digestion begins in the stomach. There, the flexing movements of the stomach wall (gastric motor skills) create an emulsion of the fats ingested. At the same time, the fats are already partially broken down by the "gastric" lipase contained in the gastric juice. It is about 10% involved in lipolysis.

2.3 Small intestine

After absorption in the small intestine, the next step is fat digestion. Fats in the small intestine stimulate the release of the tissue hormone cholecystokinin. Cholecystokinin stimulates two organs that are important for fat digestion:

The lipase is activated in the bicarbonate-rich environment of the duodenum with the help of the enzymes trypsin and chymotrypsin and breaks down triglycerides into free fatty acids and monoglycerides. The lipase can only work effectively if the dietary fats form so-called micelles with bile acids as emulsifiers.

The micelles are absorbed into the cells of the small intestine and release the monoglycerides and fatty acids in the cells. They become free again to bind new fat breakdown products in the intestinal lumen. Resynthesis to triglycerides now takes place in the cells of the intestinal wall.

2.4 vascular system

The newly formed lipids cannot leave the cell until they are surrounded by another special shell, the chylomicrons. They are made up of cholesterol and phospholipids and come from the same cell. The chylomicrons ensure that the lipids can pass the cell membrane again and get into the blood via the lymph vessels.

After a high-fat meal, the blood is cloudy due to the chylomicrons (digestive hyperlipidemia).

2.5 Target tissues

Target tissues such as liver, adipose tissue and muscles can absorb and process the fats through the action of lipoprotein lipase.

2.6 Fat excretion

The excretion of fat in the stool is 5-7 g per day. With a fat-free diet it is approx. 3 g per day. With a fat-free diet, this fat comes from flaked epithelia and bacteria.