Digestion. Not the most appetising dinnertime conversation. We don’t talk about it often, but so many of us suffer from the ill effects of digestive dysfunction.
It’s likely you’ve suffered from gas, bloating, reflux or other digestive dysfunction at some point in your life, unless of course you’ve been raised as a Tibetan monk with zero life stress, sipping on nourishing broths and noshing on your daily dose of veggies.
To break it down for you (see what I did there?!), digestion is the chemical and mechanical breakdown of food so it can be used by the body’s cells.
Digestion is a north to south process. Digestion starts first in the brain, where the sight and smell off food trigger the production of saliva.
When food enters the mouth it is broken down both mechanically (by chewing), and chemically with salivary amylase, which begins the breakdown of carbohydrates in the mouth. The salivary glands secrete saliva to moisten the food and help with swallowing.
When you swallow, the food (now called ‘bolus’) enters the oesophagus for passage to the stomach. The cardiac sphincter at the bottom of the oesophagus opens to allow the bolus to enter the stomach, where the mechanical and chemical breakdown of food continues.
In the stomach, gastric juices are secreted from millions of tiny glands located in the mucosal lining of the stomach. Hydrochloric acid and pepsinogen break proteins down. The stomach is all about acid. The normal pH of the stomach is between 1.5 and 3.0. Let’s just say your stomach acid would burn a hole through the bottom of your bathtub!
Stomach acid does more than digest your food. It disinfects the stomach, kills bacteria and parasites, triggers the release of gastrin and activates pepsin, which is required for appropriate digestion of proteins.
After the stomach churns the bolus and mixes it with gastric juice, the food is further broken down into a paste called chyme, which is very acidic. When the chyme leaves the stomach, it passes through the pyloric sphincter into the small intestine. First stop, the duodenum, where the chyme becomes almost neutral.
In the duodenum, the acidic pH of the chyme triggers the secretion of mucous. Simultaneously, the intestinal walls secrete two hormones into the bloodstream: secretin and cholecystokinin (CCK). Secretin stimulates the pancreas to release bicarbonate and pancreatic juice. Cholecystokinin (CCK) stimulates the gallbladder to release bile.
Bile breaks down and emulsifies the fats. The pancreas releases sodium bicarbonate to raise the pH of the chyme to neutral (7.0). When the chyme is neutral, the pancreatic juice is secreted to complete the chemical digestion of carbohydrate, proteins and fats. By the time the chyme leaves the duodenum, it’s almost totally digested. Carbohydrates are broken down into glucose molecules, proteins are broken down into amino acids and peptides and fats are broken down into fatty acids and glycerol molecules.
Peristalsis moves these absorbable molecules into the jejunum, where millions of villi and macro villi absorb the nutrient molecules into the bloodstream, where they are carried to the entire body. Glucose, amino acids and short chain fatty acids are carried to the capillaries and liver. Long chain fatty acids require bile for proper absorption and end up in the lymphatic system.
The leftover chyme from the small intestine, made up of indigestible fibers, bile, water and sloughed off cells, gets passed on to large intestine through the ileocecal valve.
In the large intestine, the water and waste material is recycled, with the waste material nourishing the colon cells. Any remaining nutrients are captured with the help of bowel flora and converted to Vitamins K, B1, B2, B12 and butyric acid.
Then, you guessed it! Anything still hanging around is expelled.
So, there you have it. Digestion is a long and complex process, and so much can go wrong. This is how digestion functions in a healthy individual, but for so many people today this just isn’t the case. Stay tuned for an upcoming blog post on digestive dysfunction.
Do you need support to help with digestive issues or other health concerns? I work with clients one-on-one to assess their current health and create a plan to restore their body to its natural balance. Head on over to the contact page and get in touch!