The Digestion Sessions

We all have to eat, right? But have you ever stopped to think about the effect the foods you consume have on your health, mood, energy levels and the planet? Do you know exactly where your food comes from and how it gets to be on your plate? Are you aware of how what’s in the food affects how your body functions and the impact it has on your health and wellbeing?

Every single function of our body, every minute of every day, requires nutrients.

Without nutrients in the correct form and ratios, things don’t work so well.

There are three main sources from which we get our nutrients.

Carbohydrates– a group of foods including sugars, starches and cellulose.

Carbohydrates provide fuel and energy for the cells of the body and the brain. They are digested by the enzyme amylasewhich cleaves the bonds between the sugars, breaking them down into their smallest form. Digestion of carbohydrates begins in the mouth and continues briefly in the stomach before being completed in the small intestine.

Proteins – made of amino acids, which are commonly found in meats and animal products but can also be acquired through nuts and legumes. The protein you eat is broken down into amino acids by HCl acid in the stomach and the enzyme pepsin. These amino acids are absorbed through the small intestine and combine to form new proteins which are used to help the body grow, break down food, repair tissue and perform many other body functions.

Lipids (fats)– Lipids are abundant building blocks in our body – our cells, brains and hormones are made of fat. They are also a fuel source for energy production. Digestion of fats begins in the mouth through the enzyme linguallipase. Lipids then continue to the stomach where chemical digestion continues by gastric lipase. Once digested, they move to the small intestine where pancreatic enzymes and bile finish off the digestive process, making the lipids small enough to be absorbed through the intestinal wall.

Sadly, it’s not as simple as eat the good food and get the good nutrients. A lot must happen in our body from the time we take a bite of food, to the time it comes out the other end. Our food just isn’t the same quality it once was. We have over-farmed the soil and lost the natural minerals and nutrients from our soil quality. More sprays, pesticides and chemicals are used in growing, picking, harvesting, transporting and storing raw food materials, not to mention what is done to our food when it is processed and packaged. Any wonder our foods don’t contain high levels of nutrients any more!

Decades of treating our food this way, and our over consumption of heavily processed foods, has caused our bodies not to work as effectively.

A large percentage of the population has somedegree of digestive dysfunction. This can manifest in many ways, with the most common being:

reflux/heart burn

indigestion

pain/nausea/bloating/discomfort after eating

excessive wind

altered bowel habits

food intolerances

skin conditions

headaches

Most people have had these symptoms for so long they begin to think it’s ‘normal’.

So, let’s talk about that for a minute. What does normal digestionlook like?

Basically, our digestive tract is a long, hollow tube that starts at the mouth and ends… you know where. This is pretty much it, with a few twists and turns in-between. Starting at the top, the eyes and nose are pretty important in the whole process. When you see food, think about food and smell food, it’s a signal to your mouth to produce saliva, which triggers your stomach to produce gastric acid in preparation to digest food.

But your mouth is more than just the entry point. We have three pairs of salivary glands that produce saliva to keep our mouth moist, help to digest food and provide bacterial protection for our bodies. Saliva is mostly made of water but also contains enzymes, antibacterial compounds, mucus, minerals and electrolytes. All of these things help to digest food and keep our teeth and gums healthy.

Our teeth chew and breakdown our food (masticate), reducing it to small pieces. Our tongue is a muscle that helps to move the food around our mouth and taste the different components of our food, which is very important as this sends signals further down the line as to what is coming. We have five main perceptions of taste: sweet, sour, salty, bitter and umami. The taste perceived on our tongue sends a message to the brain as to the likely types of food about to enter the gut so our body can prepare to digest and absorb the food we eat as efficiently as possible.

Our mouth and throat contain immune tissue which helps to prevent any nasties from entering the body. This is found in the form of our tonsils. (Most people are only familiar with their tonsils once they become infected – tonsillitis.) These are called your palatine tonsils, but they aren’t the only ones in there! There is a ring of immune tissue that circles the back of the throat known as Waldeyer’s ring. This tonsil group are like ‘security guards’, checking everything that comes through to make sure it is ok for the body. Anything suspect trying to sneak past is detained and dealt with by the immune system. This is what is happening when our tonsils are swollen and painful.

Once our food (now called bolus) gets past the security guards, it enters our oesophagus, a straight chute down to the right-hand side of our stomachs. The oesophagus is lined with muscular rings which stretch to accommodate the bolus and, as it moves along, the muscles contract back to their normal position once it passes, preventing things from going back up. Fun fact – These one-way muscle contractions are so strong the food will still reach your stomach even if you are standing on your head! (Please don’t try this!) The oesophagus is also sealed at the bottom end with a muscular ring known as a sphincter, the lower oesophageal sphincter to be exact. It opens briefly to allow the bolus to enter the stomach and then snaps shut again.

And now we are in the stomach – the weird lopsided j-shaped organ that sits just below the breastbone, with the heart and lungs perched on top of it. The stomach is also a muscle-lined organ, with three muscle layers which work to mix and churn the food (retropulsion). The stomach has four main areas, all with their own individual functions, and two routes the food can take. Liquids pretty much pass straight through and into the duodenum (small intestine). Some carbohydrates move through relatively quickly as well. Solid foods, which take a bit longer to digest, are sent down the other path so they can be macerated and mixed with gastric secretions to form a soupy liquid calledchyme. Carbohydrates are digested first in the stomach and pass fairly quickly down the line, with proteins and fats held longer as they require more work to digest fully.

As we all know, the stomach can stretch to accommodate food; when it is empty, it hangs loose with wrinkles (rugae). Our stomach is the stretchiest part of our digestive tract, enabling it to hold an entire meal until the small intestine is ready to do its part.

In addition to the muscular contraction of the stomach to mechanically digest our food, there is also chemical digestion taking place. The wrinkles and folds in the stomach lining form pits into which gastric juice is secreted. This gastric juice is a combination of substances produced by three different types of cells: mucus neck cells (produce mucus which keeps things moist and slimy and moving along), parietal cells (produce intrinsic factor needed for the absorption of vitamin B12, in addition to secreting hydrogen [H+] and chloride [Cl-] separately, which, when combined, produce hydrochloric acid [HCl]) and chief cells (secrete pepsinogen and gastric lipase, which are the enzymes required to break down fat and protein into their smallest form).

Once all these chemicals have dissolved the food particles and the muscles have churned, it is time to move on to the small intestine (duodenum). The bottom of the stomach has a sphincter (just like at the top) to allow macerated food to pass into the duodenum. The small intestine is where all the magic happens! This is where the whole food has become micronutrients for our body to use. The small intestine is long – anywhere from 2 metres up to 10 meters long. It is lined with specialised skin cells called enterocytesthat have hair-like projections of skin (microvilli) on them. This helps to increase the surface area of this long tube and aids with propulsion, moving the liquid onwards, all the while absorbing nutrients across the thin membrane and into the blood stream for transport around the body to be used for growth, repair, energy, maintenance and the millions of amazing things our bodies do every second of every day.

Once the food has been absorbed and any undigestible matter is moved to the large intestine, the small intestine sends in the cleaning crew. It is called the migrating motor complex (MMC) and sweeps the entire length of the tube. It can only do this when the stomach and small intestine are empty. This is why it is important to have a break between eating so the housekeeping and maintenance can take place.

Anything that is moved along enters the large intestine. Any essential nutrition has been removed from the food, absorbed into the blood stream and utilised by our body. Anything that is left is essentially a waste product and needs to exit the system in a timely manner. The large intestine is home to the greater portion of the microbial ecosystem that lives within us. This helps to further breakdown the waste product and decompose it. Sounds gross, right?!

There are no microvilli here to move things onward; the motion of the large intestine is called peristalsis. The length of this organ is divided into sections of band-like muscular rings which stretch and contract in response to the fullness of the bowel. As a section fills up, it stretches the muscle wall and the wall pushes back against the bulk, squeezing it on to the next section, until it makes its way through and out the other end.

This a general outline of what ‘normal’ digestion looks like. From here we can determine if something isn’t working well. If you have any digestive symptoms, or things just don’t feel right, book a naturopathic consult and get to the bottom of the issue.

Amanda Lorch (BHSc)

Naturopath & Kinesiologist