Digestion and Absorption of Macronutrients

How do our bodies digest and absorb macronutrients?

Carbohydrates:

Digestion: The digestion of carbohydrates begins in the mouth, where salivary enzymes break down complex sugars into simpler sugars. These sugars are then transported to the small intestine, where pancreatic enzymes further break down complex sugars into glucose and fructose.  

Absorption: The small intestine absorbs glucose and fructose and transports them to the liver, where they are converted to glycogen, stored for future use, or transported to the cells for energy.  

Metabolism: After absorbing carbohydrates, the liver converts them into glucose that supplies energy to the brain and other organs. When the glucose levels in the body become too high, the pancreas produces insulin, which then facilitates the transport of glucose to the cells for energy.

Proteins

Digestion: The digestion of proteins begins in the stomach, where it is broken down into smaller fragments by the action of acid and enzymes. These fragments then reach the small intestine, where the pancreas releases enzymes that break them down into amino acids.  

Absorption: The small intestine absorbs amino acids and transports them to the liver, where they are either used to build new protein or stored for future use.  

Metabolism: The liver converts amino acids into glucose, which is then used for energy production. Proteins are also used to build new tissues, such as muscles.

Fats

Digestion: The digestion of fats begins in the small intestine, where bile and lipase enzymes break down fat molecules into fatty acids and glycerol.  

Absorption: Fatty acids and glycerol are transported to the liver via blood circulation. Fats are also absorbed by the lymphatic system, which transports them to the bloodstream.  

Metabolism: The liver converts fatty acids into energy or stores them as triglycerides for future use. Triglycerides are stored in adipose tissues and used as an energy source when glucose levels are low.

References:

Burns, M. (2019). Macronutrient digestion and absorption.https://youtu.be/n2eCc1eHQDc?si=YnuVAWSr_3hk6ZiH