The Basics of Digestion

Our plan is to take a deeper dive into many topics, but we are going to start by building onto some of the fundamental concepts that are important to our overall health and subsequently weight loss. One of the most important topics that we are going to start with is the basics of digestion.

Many of you reported coming into this program with digestive issues, or wanting to know more about how your body may respond to the plan with issues like IBS, Crohn’s disease, GERD (Gastric-Esophageal Reflux), missing your gallbladder, gastric bypass or other modifications. So, we are going to break this all down for you in our series about the digestive system!

Why is digestion so important?

Digestion is the complex process where our body breaks down the food and liquids that we eat in the form of carbohydrates, proteins and fats, into smaller components and nutrients, which the body uses for energy, growth, and cell repair. If there are any impairments in this process, there can be an impact in how our body is able to absorb and utilize the nutrients, vitamins, and minerals that we need to maintain optimal health! This is why with The Livy Method, there is a huge emphasis on improving digestive health, eating nutritious food, and making all meals and snacks as nutrient dense as possible.

The cephalic phase:

Many of us don’t realize this, but digestion actually starts in our brain! When we think about, see, smell, touch, or taste food, our hormones become activated. We begin to secrete saliva in our mouths and our stomachs begin to secrete gastric juices. In fact, this phase is responsible for the secretion of up to 50% of our gastric and digestive hormone secretions, in order to aid in the processing of what we eat (Zafra, M.A., Molina, F., & Puerto, A., 2006)!

This is where our mindfulness should really start, in order to take full advantage of the optimal digestion of our foods. We can do this by checking in with ourselves to see what ingredients appeal to us most, taking the time to prepare our foods thoughtfully, and using all our senses in the food preparation process. Be in the moment and enjoy it!

Thus, the cephalic phase is a perfect time to really dive into the first two mindfulness questions of eating: Are you feeling hungry? How is this portion for me?

The eating phase:

The next phase of digestion continues to the mouth with the ingestion of food. This is where we begin to chew our foods and saliva continues to flood into our mouths. The action of chewing with our teeth helps to break down the foods we are eating into smaller bits for our body to process, mixing with enzymes contained in our saliva. “Enzymes” are special proteins we have in our body that help speed up certain chemical reactions, and are involved in helping to build certain substances or break them down (like in the case of digestion).

Although we have multiple glands that produce saliva and enzymes, the parotid gland is most responsible for producing amylase (the enzymes that help break down carbohydrates into glucose). Our saliva also provides lubrication to help our food to travel down our digestive tract. The most important part of this phase is the act of chewing, as it allows for good mixing of the broken-down food with the saliva and enzymes. It also does some good work of breaking down the food before it enters our stomach. The big takeaway here is, the better we are able to chew our food, the better our bodies are able to process it!

This is where we can really tune into the third set of mindfulness questions; Are you getting full? Is this food satisfying you? How would you feel if you took a few more bites? How would you feel if you stop eating now? Do you feel any physical effects of eating? Doing this allows us to chew our foods from our meals and snacks as they were meant to be chewed, instead of rushing through the process.

This is really important when we are eating those 4-5 token bites when we aren’t hungry, in order to get the digestive process going. Which is why it is recommended to chew, chew, chew, chew, chew, chew, chew, chew with every bite while having our token bites!

The process of digestion

Esophagus & stomach

When we swallow the food we have chewed (which is now called a “bolus”), it passes through our throat via the pharynx to the esophagus. The esophagus is a smooth muscular tube that is attached from our throat to our stomach that uses involuntary muscular contractions to propel the bolus to our stomach. This process is called peristalsis.

Once the food enters into the stomach, the cells in the stomach lining begin to secrete gastric juices that are rich in HCl (Hydro-Chloric Acid). This increases the acidic environment of the stomach and activates pepsin, the enzyme responsible for breaking down protein into amino acids. Amino acids are then able to be used by the body as building blocks for vital processes such as building proteins, hormones, and neurotransmitters.

This acidic environment is also important for our immunity/defense system, as it creates an inhospitable environment for bacteria and other pathogens to grow, thus keeping us healthy!

The stomach begins to churn and contract, and that food we worked so hard to break down by chewing, forms a semi-liquid form of partially digested food called “chyme”.

The small intestine, the liver, the gallbladder, and the pancreas

The stomach stores the contents of the chyme, and it is slowly emptied into the small intestine. The small intestine is divided into three different segments, known as the duodenum, the jejunum and the ileum.

The chyme first enters our duodenum (the first part of our small intestine) at a rate of about two teaspoons per minute. The duodenum receives enzymes from a variety of organs also involved in the digestive process; the liver, the gallbladder, and the pancreas.

The liver is a large organ located above the stomach in the upper abdomen. The liver produces bile which is stored in the gallbladder, stores nutrients, and helps remove toxins from the body.

When we eat fatty foods, the gallbladder (a small pouch) is stimulated to secrete bile via the bile ducts to the small intestine, which helps to emulsify the fats and makes it easier for lipases (enzymes that break down fat) to do their job!

The pancreas which is located in the upper part of the abdomen, behind the stomach, secretes what is known as “pancreatic juice.” This juice contains a substance called bicarbonate (which helps to neutralize the high acidity of the incoming food) and pancreatic enzymes. These pancreatic enzymes include protease (which breaks down protein) as well as amylase and lipase which have been discussed earlier. The pancreas also produces chemicals that help regulate blood sugar levels, which affect how much energy the body has available to use. One of these is the infamous insulin, which we will discuss in more detail in our series.

The small intestine also secretes its own enzymes for digestion known as peptidases, sucrase, lactase and maltase. These enzymes contribute mostly to the hydrolysis of polysaccharides, meaning they use water to break down these longer chain carbohydrate molecules into simpler sugars like glucose.

Once our food has been broken down into the basic building blocks of glucose, amino acids, vitamins, minerals, and fatty acids, they are ready to be absorbed into our bloodstream which carries the nutrients to cells throughout the body! The small Intestine is where most of digestion and absorption take place. The chyme moves in rhythmic movements along the intestines to allow for the mixing of fluids, and for a longer period of time for digestion to take place. The walls of the intestines are lined with finger-like projections called villi, which are then lined further with even tinier finger-like projections called microvilli. These allow for an incredibly expansive surface area for all of this absorption to take place, providing your body with those super important nutrients and energy!!!

The large intestine

The last phase of digestion is the movement of the remaining undigested food into the large intestine (otherwise known as the colon) into the formation of stool or poop. The colon is primarily responsible for the reabsorption of water and the last bit of nutrients from this final stage of processing food, the content that remains forms stools which we poop out through our rectum via the anus.

The colon also contains our gut flora which is composed of trillions of microbes known as the microbiome. This is definitely a hot topic around here with our members, and a topic we will be looking further into down the road. These bacteria help to ferment the indigestible food and produce vitamins such as Vitamin K and B vitamins that are reabsorbed by the colon. But that’s not all, an estimated 80% of our immune system is found in our gut (Wiertsema SP, Van Bergenhenegouwen J, Garssen J, Knippels, 2021). Having a healthy digestive system, which includes a good balance of our healthy gut flora, ensures a healthier immune system and better nutrient absorption. This is why the Livy Method recommends taking a good quality probiotic, along with a prebiotic (if needed), to help feed those good microbes. Eating the high fibre, nutrient rich foods on plan not only gives our body what it needs, but is also vital in supporting our gut flora.

For a comprehensive video looking at digestion, check out this video:

https://www.youtube.com/watch?v=X3TAROotFfM

The last question in mindfulness

This sums up the topic of the basics of digestion, and brings us to the fourth series of questions in mindfulness when eating. Do you feel full and if so, what is your definition of full? How do you know when you have eaten enough? How do you feel physically? Meaning, is it a physically full belly feeling, or is it more of an insulin rush or a tired feeling? Or is it that you just eat everything on your plate because it’s there kind of thing? Or maybe you feel like you could eat more?

As you can see, establishing mindfulness around your eating not only helps you connect and become more in tune with your body, but additionally promotes optimal digestion! Hope this helps!

Now that we understand the basics of digestion, we will build upon this knowledge in the coming weeks. However, next week we will initiate the conversation regarding the concept of “effort”, and how the psychology of effort can impact our weight loss journey and process.

References

Anatomy of the digestive system. (2017). BarCharts, Inc.

Azzouz, L.L., & Sharma, S. (2021). Physiology, large intestine. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK507857/

Boland, M. (2016). Human digestion - a processing perspective. Journal of the Science of Food and Agriculture, 96(7), 2275–2283. https://doi.org/10.1002/jsfa.7601

Granger, N.D., Morris, J. D., Kvietys, P. R., & Granger, J. P. (2018). Physiology and Pathophysiology of Digestion. Morgan & Claypool Life Science Publishers.

McClements, D.J. (2019). Future foods: How modern science is transforming the way we eat. Copernicus Publications. https://doi.org/10.1007/978-3-030-12995-8

Morris, J.D., Granger, D. N., Granger, J. P., & Kvietys, P. R. (2018). Physiology and Pathophysiology of Digestion: Part 2. Biota Publishing.

Prados, A. (2022, February, 2). Four science-backed ways of taking care of your gut microbiota. Gut Microbiota for Health. https://www.gutmicrobiotaforhealth.com/four-science-backed-ways-of-taking-care-of-your-gut-microbiota

Schwenke, T. (2020, May 3). Human digestive system - How it works! [Video]. Youtube. https://www.youtube.com/watch?v=X3TAROotFfM

Sethi, S., & Jewell, T. (2019, February 1). What causes dysbiosis and how is it treated? Healthline. https://www.healthline.com/health/digestive-health/dysbiosis

Your digestive system & how it works. (2017, December). National Institute of Diabetes and Digestive and Kidney Diseases. Retrieved March 30, 2022, from https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works

Zafra, M.A., Molina, F., & Puerto, A. (2006). The neural/cephalic phase reflexes in the physiology of nutrition. Neuroscience and Biobehavioral Reviews, 30(7), 1032–1044. https://doi.org/10.1016/j.neubiorev.2006.03.005