Macronutrients and Digestion

Now that we know a little bit about macronutrients and their sources, let's talk about how they get from our plate to where they need to go in the body.  The food we eat must be broken down into smaller nutrients of carbohydrate, protein, and fat, in order to be absorbed by the blood and then the cells. 

Here is an illustration to look at while I explain how these nutrients are digested and absorbed.

("Digestive System Basics," 2014)

Digestion begins in the mouth as we chew our food.  Saliva mixes with the food so it travels through the digestive system with ease.  An enzyme in saliva also begins the process of digesting starch.  The chewed up food is now called a bolus and, once swallowed, is sent through the esophagus to the stomach.  In the stomach, more liquid and digestive juices are added and it remains there for three to five hours.  Stomach acid in the lining of the stomach begins breaking down protein.  Contractions of the muscles in the walls of the stomach are responsible for the churning and mixing of the food and liquid.  This mixture is now called chyme.  Muscle contractions called peristalsis send the chyme to the small intestine.  More digestive juices from the pancreas, liver, and intestine itself are added in the small intestine.  The juices from the pancreas and the liver start to breakdown fats.  Juices from the pancreas and the small intestine continue to work on carbohydrates and protein.  Nutrients are now absorbed through the intestinal walls.  Protein and carbohydrate are sent to the liver through the bloodstream while fat travels via the lymphatic system for absorption (Wallace, 2013).

References

Digestive system basics [Digital image]. (2014, September 21). Retrieved from http://discoveringhealthy.com/

Wallace, M., MD. (2013, September). Your Digestive System and How It Works. Retrieved from http://www.niddk.nih.gov/health-information/health-topics/Anatomy/your-digestive-system/Pages/anatomy.aspx