Today I’d like to talk about one of my favorite topics – digestion! It is my belief that no matter what ailment you are trying to treat, you cannot get better until you work on improving your gut. Bad digestion has tons of downstream effects, which we will talk more about in Part 2!
Today’s post is to explain everything that should be happening when digestion works properly. A very important concept is that digestion is a North to South process. I know, this seems obvious, but basically this means digestion starts in the brain and continues South. Most importantly, if anything goes wrong in this process, it means things won’t be working properly the entire way through.
The brain is a very important part of the digestive process! The sight and smell of food triggers our salivary glands to begin producing saliva.
There are two parts of the Autonomic Nervous System that are important to understand for digestion, they are the Parasympathetic Nervous System and the Sympathetic Nervous System, you can think of these as the “rest and digest” and “fight or flight” systems respectively.
The Sympathetic Nervous System kicks in when we are in a stressful situation and shuttles blood away from digestive system and non-essential functions and toward the heart, lungs, and limbs. This increases your heart rate and makes more energy available to your muscles so that you are ready to either fight or flee the stressful situation you have encountered.
The Parasympathetic Nervous System on the other hand restores balance to the body and allows it to relax and repair. This is the ideal state for digestion and is triggered by relaxation, rather than stress.
In the mouth saliva begins to chemically break down starches, and chewing breaks down food mechanically. Once you chew and swallow your food, it is referred to as a bolus.
Once the bolus reaches the stomach Hydrochloric Acid and Pepsin are secreted to break down the proteins in the food into peptides.
The stomach is designed to be a very acidic environment, and Hydrochloric Acid helps kill bacteria and parasites and break down proteins. Without it we are more susceptible to infection and our food may move throughout our system not fully digested.
Once the HCl and Pepsin have finished breaking down the food into a paste called chyme, it is released into the duodenum.
The Small Intestine
The chyme is released into the duodenum, the first part of the small intestine where absorption starts to take place. The acidity of the chyme triggers the small intestine to secrete mucous for protection, and the hormones Secretin and Cholecystokinin (CCK).
Secretin stimulates the Pancreas to release sodium bicarbonate, which will make the chyme less acidic so it doesn’t cause ulcers as it travels through the rest of the intestinal tract. It also stimulates the Pancreas to release digestive juices which contain enzymes to complete the breakdown of carbohydrates, fats, and proteins.
At the same time, CCK stimulates the gallbladder to release bile, which is necessary to break down and absorb fats.
When the chyme leaves the duodenum it is fully digested and moves through the small intestine via peristalsis, which is a contraction of the small intestine. Throughout the small intestine are millions of villi, which are small, finger-like projections on the surface of the small intestine, that absorb the nutrients from the food and take them into the blood stream.
The Large Intestine
The leftover chyme from the small intestine, which contains water, bile, indigestible fibers, and more, get passed into the large intestine through the ileocecal valve.
From here, the large intestine recycles the water and waste materials, captures any lost nutrients that are still available and with the help of the bowel flora converts them into vitamins, and finally forms and expels feces.
And that is the process of digestion!
Stay tuned into the series to see what goes wrong in digestion and how we can fix it, and leave your questions in the comments below!