Digestion 101

Introduction

A properly functioning and healthy gut is as the roots of a tree are to health. If the roots of the tree aren’t healthy, the tree may suffer in its ability to be strong, grow, maintain healthy bark and leaves, and get the nourishment it needs to survive. Likewise, if the health of the gut is compromised, it may lead to feeling unwell, susceptibility to illness, nutrient absorption issues, and the development of disease. It is a highly complex system, so let's first understand how it works.

What is the digestive system?

Another word for the digestive system is the gastrointestinal tract, or GI tract. It extends from the mouth to the anus and includes the hollow organs of the mouth, esophagus, stomach, small intestine, large intestine, and anus; and the solid organs such as the liver, pancreas, and gallbladder.

The small intestine includes 3 parts:

• duodenum

• jejunum

• and ileum.

The large intestine includes:

• the appendix

• cecum

• colon

• and rectum.

In addition to the organs, nerves, hormones, blood, and bacteria work together to help digest foods and beverages consumed each day.

The digestive system breaks nutrients consumed (carbohydrates, fat, protein, vitamins, minerals, water etc.) into smaller pieces that the body absorbs and uses for energy and lots of other important functions. Proteins break down into amino acids. Fats into fatty acids and glycerol, and carbohydrates into simple sugars. As food moves through, each part of the GI tract is responsible for breaking it down into smaller pieces. In the large intestine, water is absorbed, and the waste products are formed into stool.

Check out the infographic below to learn more about how digestion works. This is an oversimplification and does not include a view of the gut-brain axis.

What happens to the nutrients?

The SI absorbs most of the nutrients and the blood, or circulatory system, passes them to the other parts of the body for use or storage.

Some nutrients are absorbed directly across the intestinal lining into the bloodstream. Simple sugars, amino acids, glycerol, salts, and some vitamins are carried to the liver via the bloodstream. The liver will then process the nutrients and share them with the rest of the body when needed.

The lymph system absorbs vitamins and fatty acids. This is the system that helps to carry white blood cells through the body.

The body will use amino acids, glycerol, fatty acids, and sugars to build substances needed for growth, energy, and cell repair.

References

National Institute of Health, National Institute of Diabetes and Digestive and Kidney Diseases. (2017). Your Digestive System & How it Works. Retrieved from https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works

Slide show: See how your digestive system works. (2020, January). Mayo Clinic. Retrieved from https://www.mayoclinic.org/digestive-system/sls-20076373?s=7