Lipid digestion, transport, and storage in humans

Lipids

How are lipids processed in the human digestive tract?

Digestion of lipids minimally begins in the mouth, as salivary lipase initiates digestion of some of the shortest fat chains. Most lipids remain undigested through the stomach as well. Lipids are first fully absorbed by the small intestine in order for them to be used as part of the diet. In the stomach, lipids separate from the rest of the food, easing passage into the small intestine by floating in the chyme. Lipids are oils and are therefore insoluble in the intestine. Bile salts, which are that are made from cholesterol in the liver, stored in the gall bladder, and secreted after the ingestion of fat, facilitate the emulsification of lipids. Furthermore, this emulsification of lipids allows them to be accessible to pancreatic lipases. Fats are enzymatically digested by pancreatic lipases into glycerol, fatty acids, and monoglycerides. Digested lipids form spherical complexes called micelles, which are processed in the intestines into triglycerides and packaged into chylomicrons for export in lymph.

What are the enzymes involved in lipid digestion?

Certain enzymes are secreted for lipid digestion and result from lipid digestion at certain points in the digestive system. Throughout the digestive system, these enzymes include: triglycerides, lecithin, lysolecithin, salivary lipase, pancreatic lipase, intestinal lipase, and lecithinase.

How are these byproducts transported throughout the circulatory system?

The byproducts of lipid digestion are transported through the circulatory system by chylomicrons, which carry digested lipids from intestine into lymph, and ultimately through the circulatory system to the liver for further processing and repackaging.

How do unsaturated and saturated fatty acids differ from each other?

Saturated fats contain carbon atoms with a single bond between them and as many hydrogen atoms as possible bonded to the carbon atoms. Saturated fats contain carbon atoms with a double bond, and can therefore absorb more hydrogen atoms. Healthy diets are low in saturated fats, since they raise blood cholesterol levels.

What are the roles of Essential Fatty Acids (EFA) in humans?

There are two essential fatty acids: the omega-3 fatty acids and the moega-6 fatty acids. The roles of EFAs include assurance of healthy growth, skin health, kidney and liver health, and reproductive health.

What are the sources of EFA in the diet?

Omega-6 fatty acids are found in sesame, corn, flax, safflower, and sunflower oil, as well as free range meats and eggs. Omega-3 fatty acids are found in cold water fish, dark leafy vegetables, and some vegetable oils, such as flaxseed oil.