9 Facts About the Digestive System

Food goes into our body. A few hours later, food comes out of our body. The digestive system does its work in between. Simple. Right?

Well, wrong.  

The digestive system may seem like a simple part of our body that helps in processing food. But, in reality, it is far more complex and interesting.

The digestive system is deemed to be a highly responsive and intelligent biological system that highlights the brilliance of nature’s design.

What else?  

Every inch of this system works in unison to keep you healthy, nourished, protected and energised.

Here are nine fun facts about the digestive system—              

1. The digestive system starts working even before you put any food (or drink) in your mouth.

Most people believe that digestion begins after we consume the food.

Some people even go for slow-paced walks after consuming a heavy meal because they think that it might aid in digestion.

Though going for a walk does help with digesting our food, the process of digestion begins much earlier than the post-consumption stage.

In fact, the initial stages of digestion begins before we even put any food in our mouth. The process of digestion begins in our brain.

How, you may ask?      

When you smell, see or even think of a tasty food, it triggers a neurological response that basically sets your whole digestive system in motion.

This chemical reaction and actions in the brain and body is known as the cephalic phase of digestion.

This is how digestion works.  

Once your senses register any food (especially the tasty ones), your brain sends signals through the vagus nerve to your stomach and the salivary glands.

Your body starts producing saliva that is packed with an enzyme called salivary amylase. This is when your mouth starts watering.

Salivary amylase performs the function of breaking down complex carbohydrates into simple sugars, right on your tongue before the food even reaches your stomach.

At the same time, your stomach starts releasing gastric juices and contracting in anticipation of the incoming food.

In a way, your body is “pre-heating the oven” to process whatever food you put in it.

And by the time you start chewing and swallowing your food, your digestive organs are ready and waiting to receive and process it.

2. The digestive tract is super-long.

When we hear the words digestive system, the first thought that comes to our minds is that of the stomach. And we often picture it as an individual organ.

However, the digestive system is not just the stomach. It is a long hollow tube that continuously runs from your mouth to the end of the large intestine; which is the anus.  

In fact, in adults, the digestive tract is about 9 metres (appx. 30 feet) long!

So, when the question is, how long is the human digestive tract? The answer is, very very long!

The length of the digestive tract needs to be extremely long as the whole process of breaking down food and deriving the required nutrients from it is a demanding job.

Each section of the uber-long digestive tract has a specific task to perform. The digestive tract is basically a giant biological food processing plant.

The mouth is the entrance, the esophagus is the elevator that takes food down to the stomach, the stomach is the blender that churns and breaks down the food, the small intestine is where the nutrients from the food is absorbed, and the large intestine is the water-recycling and waste-management section.

Food travels down this long internal highway at a slow pace.

This slow pace is crucial in ensuring that your body has enough time to obtain every single calorie, vitamin and mineral before the remaining material is expelled.

If you ever thought, what does the digestive system do? Now you have your answer.        

3. The gut has its own nervous system that can influence your mood.

One of the lesser known digestive system facts is that the digestive system (the gut) has its own independent nervous system.

It is called the Enteric Nervous System (ENS). It is made up of more than 100 million nerve cells that are embedded in the walls of the digestive tract.

For reference, that is more nerve cells than the ones present in the spinal cord!

The ENS is in constant communication with your brain through the vagus nerve. But the ENS is perfectly capable of operating on its own accord.

It oversees functions like local blood flow, digestion and sensing the nutrients present in the food that is moving along the digestive tract.

What’s more?

The gut is where the majority of the neurotransmitters are produced. As much as 95% of serotonin is produced in the gut.

Serotonin supports the regulation of mood, emotions and sleep.        

Hence, we get a “gut feeling” before making a big decision, and have “butterflies in the stomach” when we are nervous or excited about something.

Also, when there’s an imbalance or irritation in the digestive system, certain neurotransmitters can send strong signals to the central nervous system.

As a consequence, it can negatively affect your stress levels, anxiety and mental health.          

4. The small intestine does the majority of the work, not the stomach.

A surprising fact about the digestive system is that the true hero is the small intestine. After all, it does most of the essential work of the digestive system.

Though the stomach gets all the credit for digesting the food we consume, it is more of a blender and a temporary container that holds the food after breaking it down.

The small intestine carries out the most important job— which is to absorb the nutrition from the food moving through it.

In fact, the small intestine performs about 90% of the entire process of digestion and nutrient-absorption.

Even though its name is small intestine, it is about 20 feet long, and has a diameter of about 1 inch.

The most fascinating thing about the small intestine is the texture of its internal surface.

The inside of the small intestine is not smooth at all. It is covered in millions of uber-tiny, finger-like protrusions named ‘Villi’.

And these villi are covered in even smaller protrusions named microvilli.

This folded, complex marvel of a biological design increases the small intestine’s surface area to a great extent.

If the entire lining of a human’s small intestine were to be unfolded and flattened out, it would easily cover an area that matches the size of a standard tennis court.

That’s how humongous our small intestine is!  

The huge surface area of the small intestine is vital in ensuring that when broken down food passes through it, the bloodstream can absorb all the vitamins, amino acids, fatty acids, and minerals efficiently.          

5. The acid produced in your stomach is so strong that it can dissolve metal.

An absolute mind-blowing fact about digestion is that the acids in the stomach that help in digestion are super-powerful.

It holds the capacity to dissolve even metal!

When food moves down the esophagus and goes into the stomach, it faces an extremely acidic environment.

The gastric juices in the stomach form an acidic liquid that is mostly made out of potassium chloride, sodium chloride and hydrochloric acid (HCl).

This acidic liquid is so potent that it can even dissolve a steel razor blade or a piece of zinc in just a few hours.

The acidic liquid in the stomach usually has a pH level between 1.5 and 3.5.

So, how does stomach acid work?

The intense environment of the stomach is vital for two reasons—

a. Breakdown of protein.

It provides the perfect conditions for pepsin (a digestive enzyme) to get activated and start breaking down the hard protein chains absorbed from food.

b. Sterilisation.

Stomach acids act as a defence system that destroys numerous harmful viruses, bacteria and parasites that may have entered your body with the food you consume.

Now, you must be wondering that if stomach acid is so strong, how does the stomach avoid digesting itself?

The stomach wall is coated in a thick, alkaline mucus layer that neutralises the acid upon contact.

So, in a way, a constant barrier is created. And it protects the stomach’s tissues from getting dissolved by its own acidic liquids.

6. A majority of your immune system is located in your gut.

The term immune system usually brings images of white blood cells to our minds. But the truth is that about 70% - 80% of the body's immunity cells reside in the gut.

In a way, the gut (digestive system) is the main headquarters of the body’s defence system.

Now, isn’t that an interesting fact about the stomach?

Every time we eat some sort of food, we inevitably expose our stomach to toxins, foreign substances and environmental microbes.

To protect ourselves from this persistent threat, our stomach has GALT.

The tissue lining the intestines contains a specialized system called Gut-Associated Lymphoid Tissue (GALT).

Its function is to distinguish between harmless food particles and certain dangerous pathogens that invade our body and can be quite harmful for us.

7. The large intestine contains trillions of microbes.

The large intestine plays an important part in the digestive process. It houses a humongous microbiome called the gut microbiome.  

A  gut microbiome fact is that it is a whole ecosystem comprising about 38 trillion bacteria, viruses, fungi and other types of microbes.

The weight of all these bacteria etc. is approximately 2.2 kgs. That is heavier than the human brain!

The micro-creatures living in the microbiome are not invaders. They are actually an integral piece of the digestive system.

Our body is not capable of breaking down complex carbohydrates and fibres.

When these indigestible components reach the large intestine, the bacteria present there ferments them.

Then, it gets transformed into short-chain fatty acids. The lining of the colon draws the necessary nutrition from those fatty acids.

What’s more?

The microbiome plays a crucial role in synthesizing essential nutrients that the body just can’t produce without the extra help.

Those nutrients include several B Vitamins and Vitamin K.

A healthy microbiome is uber-important for the digestive system to keep running smoothly.

8. The colour of your stomach sync-in with your actions and emotions.

An amazing fact about the digestive system is that it is a very expressive organ.

Most of the time, the stomach mirrors your physical as well as your emotional state simultaneously.

The lining in the stomach contains a dense network of blood vessels.

When you smell or see food, your stomach begins the preparation for the digestion of that food.

A part of the preparation includes increased blood flow to that part of the stomach.

And as a result, the internal lining of your stomach begins to “blush”. Hence, its colour changes from its resting pale pink color to a deep red colour.

When you are under a lot of stress or receive a piece of bad news, you can feel your stomach “drop”.

The reason is that when you face a negative emotion (anger, fear, anxiety etc.) suddenly, your body goes into a “fight or flight” mode. It is a survival mechanism.

When a person is going through a “fight or flight” mode, the sympathetic nervous system redirects blood away from non-urgent systems like digestion, and takes it towards your leg and heart muscles.

When blood supply is cut suddenly, the inner lining of your stomach turns pale white instantly.

So, basically, the colour of your stomach keeps changing with your changing emotions, experiences and actions.

9. Gravity does not have much influence over the movement of food through the digestive tract.

Many people believe that food falls down into your stomach because of gravity. But that is a huge misconception.

In reality, the digestive system is equipped with a highly sophisticated and involuntary muscular mechanism that is responsible for moving food through the digestive tract.

This muscular mechanism is called peristalsis.

Peristalsis is so powerful and directional that theoretically you can eat a full meal, swallow it, and digest it normally while you hang upside down from a tree branch.

Peristalsis also allows astronauts floating in space in zero-gravity to eat and swallow their food without too much hassle.

Peristalsis is basically a series of rhythmic muscle contractions and relaxations that mimics the movement of waves.

The muscles in the walls of the esophagus, stomach, large intestine and small intestine contract in a sequence, shrinking the breadth of the digestive tract, trailing a ball of food (called a bolus), and pushing it forward into the next relaxed segment of the digestive system.

Digestive System FAQs

Which drink is best for digestion?

Lukewarm lemon water is deemed to be the best drink for digestion as it stimulates the digestive enzymes.    

However, if you are suffering from bloating and nausea due to indigestion, then having a nice warm cup of ginger tea would be more beneficial to you than having lemon water.

What are the 5 main functions of the digestive system?

The five primary digestive system functions include—

a. Ingestion (ingesting food).

b. Propulsion (moving food through the digestive tract).

c. Digestion (breaking down the ingested food).

d. Absorption (absorbing the nutrients from the food).

e. Defecation (eliminating the waste from the body).            

What are the three types of gut?

It has been found that there are three different types of human digestive system or gut. Those are— Sensitive, Balanced and Dysbiotic.

The kind of gut a person possesses can be found out through the testing of that person’s microbiome.

The specific type of gut a person has is determined by her stomach’s microbiome’s bacterial diversity, balance and the presence (or absence) of key microbial groups.

Gut-types are crucial while performing various bodily functions such as digestion, metabolism, immunity, and mood regulation.

Which organ kills bacteria?

Studies have shown that the stomach is the main organ that is responsible for killing off any harmful bacteria that might have been ingested while consuming food.

The stomach uses HCI (hydrochloric acid) to kill off the bacteria. HCI is highly acidic and hence, highly efficient in doing this job.

Other organs that help in killing the harmful bacteria entering the body are the liver and the lymph nodes.              

Are our stomachs full of acid?

In short, yes. Our stomachs are full of acid.

To be precise, our stomachs primarily contain hydrochloric acid (HCl). It also has some amounts of potassium chloride and sodium chloride.

The acid in our stomach has a high pH level of 1.0 to 3.0.

Theoretically, the acid in our stomachs is strong enough to dissolve metals!          

How to improve guts?

If you want to improve your guts, you need to take care of the microbiome within.

In order for your microbiome to thrive, there are a few things you need to adhere to.

Those things include—

a. Keeping yourself well-hydrated.

b. Eating whole foods (whole grains, lean meats, minimize processed foods, reduce sugar intake, etc).

c. Including various types of fruits and vegetables in your daily-diet.

d. Making positive lifestyle changes (quit smoking, reduce alcohol intake, exercise, etc).

e. Manage your stress levels (meditate, get a relaxing hobby).  

What are signs of poor digestion?

The common signs of poor digestion are stomach pain, frequent bloating, irregular bowel movements (constipation or diarrhea) and flatulence (passing gas).      

What takes 30 minutes to digest?

Usually, the vegetables that have a high water-content are digested in approximately 30 minutes. For example, tomatoes, peppers, zucchinis and cucumbers.    

In 30 minutes, the above-mentioned foods are ready to leave the stomach and move further in the digestive tract.

30 minutes is considered to be a short time when it comes to digestion of food.    

How does age affect the digestive system?

As a person reaches a certain age in their life, some of the muscles in their digestive system tend to get weaker.                

As a result, the digestive system may not be able to carry out its functions the way it should.

However, by paying close attention to their diet and maintaining a healthy lifestyle, they can keep their digestive system in good shape.

It is very important for the elderly to remain active. A simple walk on a daily-basis can go a long way in keeping them healthy (including their digestive system).

Pun intended.