Gut Health 101
Understanding the Digestive System and How It Works
The short version: Your digestive tract runs from your mouth to your anus and is controlled by your brain and nervous system. It determines how your body reacts to, breaks down, absorbs, and eliminates the food -- and the nutrients -- you eat.
According to Johns Hopkins Medicine, the top ways to support your digestive system are: Eat the "right" foods; Get more sleep; Move more; Manage stress; and Get help for anxiety and depression. (Hmmm...sounds familiar!)
But if you search "digestive health" or "gut health" online, you'll find lots of enticing products to help you "heal your gut" and test your gut microbiome, because the wellness industry is all about selling you solutions to problems you probably don't actually have. Before you shell out for pricey at-home test kits or sign up for colon irrigation, read on to get a better idea of how your digestive system should actually work.
Let's break it down.
Gastrointestinal Tract: What It Does
The GI tract breaks down the food we eat, sorts nutrients based on where they need to go, and transports them throughout the body for use, storage, or excretion.
Gastrointestinal Tract: Why It's Important
In addition to the very important work of digesting food, the GI tract also:
processes the nutrients from food
acts as a barrier against pathogens and detoxifies potentially harmful substances
eliminates waste
secretes certain hormones
helps regulate the immune system
But it's not just about food! The gut also has a "second brain" known as the enteric nervous system. It's like a sub-nervous system that lets the main brain know what's happening in the body, and it's impacted by emotion. Those "gut feelings" are real!
Gastrointestinal Tract: How It Works
One thing these digestive system diagrams leave out is that the process of breaking down food begins in...the brain.
That's right, before you even start chewing, your brain signals your body to get ready to eat. When we smell something that smells like good food, or we see photos of appetizing meals, our brain cues saliva production aka makes our mouth start watering.
This is super interesting when it comes to feeling out of control around food or always hungry. How many times a day do we see commercials and billboards for food? How many times have you driven past a fast food restaurant and smelled French fries or fried chicken and "needed" to stop?
(This was one of the biggest Aha! moments for me when I was studying for my nutrition coaching certification. No wonder many of us have "issues with food" -- our brains are constantly receiving signals that it's time to eat!)
Once you actually put the food into your mouth, you start to break it down through a combination of chewing and the enzymes in saliva. If you have dental issues, those can affect your ability to digest properly, and on the flip side, problems with teeth, gums, and bad breath can be indicators of digestive problems further down the GI tract.
After food is broken down and swallowed, it travels through the esophagus from the mouth to the stomach. This is another area where many people experience issues with heartburn and reflux. Those occur when the muscle at the bottom of the esophagus opens too often or at the wrong times.
Reducing processed fatty foods in one's diet may help alleviate symptoms of acid reflux because dietary fat relaxes the muscle at the base of the esophagus and also slows the process of emptying the stomach, which can create pressure that pushes stomach acid up to the esophagus.
Once the food particles hit the stomach, they're blasted with stomach acid that's just about as acidic as battery acid, which kills pathogens and further breaks down food. It takes about 1-4 hours for food particles to leave the stomach. Factors like stress, medication, overeating, and hormones can also impact transit time.
Carbohydrates are quickest to be broken down, then protein, followed by fats and fibers, and liquids have a shorter transit time than solids. This is why eating higher protein and higher fiber foods is recommended for weight loss, because they take longer to leave the stomach and lead to feeling full for longer. If you're headed into a workout, on the other hand, you'll want something like a protein shake and quick digesting carbs so your snack isn't sitting in your digestive tract causing discomfort while you're trying to exercise!
After the stomach, the next step is the small intestine where most nutrients are absorbed. The small intestine is lined with brush-like cells called villi. If these "brushes" are damaged because of things like food poisoning, inflammatory bowel disease, celiac disease, etc., it can lead to problems absorbing nutrients.
The large intestine is the final stop before waste is excreted from the body. Part of its job is to ferment fiber, sugar and sugar alcohols, and other dietary carbohydrates that the small intestine can't process and in doing so, produces gas.
If you've ever heard someone say they cut down on carbs and experienced less gas and bloating, that's probably why! The actual process of digesting carbs produces gas, but that doesn't mean carbs are "bad" for you; it just means the bacteria in your large intestine is doing its job.
Actual food intolerances can also cause bloating along with other symptoms. Intolerances occur when a person lacks the enzyme to digest certain foods; for example, those who are lactose intolerant don't have the lactase enzyme that helps break down dairy. Intolerances are different than food allergies, which trigger an immune response that is immediate and can be life-threatening.
Digestive Distress?
If you're experiencing GI issues, start monitoring and tracking your intake, as well as other factors like stress levels, and try to notice patterns. Digestive troubles that are often blamed on foods can also be due to genetics, activity level, age, food intolerances, or a person's unique microbiome.
Eat slowly and mindfully. Eating too fast can override hunger and fullness cues and lead to overeating, which can cause gas and abdominal discomfort.
Eat less processed whole foods when possible. This helps ensure you're also getting the water and fiber content that aids digestion.
Address nutrient and fluid deficiencies. Aka drink your water and make sure you have adequate electrolytes.
Work with a gastrointestinal specialist and/or a registered dietitian. Someone selling supplements and colon cleanses on the internet is probably not qualified to help -- also, over-supplementation can harm the liver, and most cleanses just make you go to the bathroom a lot. They're not "detoxing" you -- your digestive system already does that! Please consult an appropriate medical expert, not Google or an Instagram influencer, any time you have health concerns.
