The Basics | Digestion, Part I

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Basics, Digestion Part I | Nutrition Stripped

It’s been awhile since I’ve added to The Basics and I’m glad it’s making a comeback with this topic, Digestion! Digestion is one of my absolute favorite topics to talk about yet it’s also incredibly dense and I could probably go on for 10 blog posts or more. Hence why writing these in The Basics gets tricky for me, knowing how to make it easy for you to understand and take home points that you can actually utilize in your life. Okay, let’s break this down!

 It’s all about, gut health.

In a perfect world, we would eat our food, it would digest well with little to no side effects like bloating, diarrhea, constipation, cramps, etc.; and our bodies would be able to pull out all the nutrients from the food and utilize it as intended. But unfortunately, it’s not a perfect world and our digestive systems go through so much “wear and tear” over the years that it affects how efficient our digestive system operates and how our bodies absorb key nutrients from our delicious and healthy food. Things like hormonal shifts, stress in our life (oh goodness I could write an entire blog post about how stress affects our digestion!), activity, genetics, food intolerances (if any), vitamin and mineral status, metabolism, thyroid health, chronic diseases/any illness, medication use, supplement use, sleep, environmental toxins/everyday exposure, antibiotic use as infants, and of course what we put in our bodies with food; all of these factors have an impact on our digestion. Before we cover things we can control and ways to make our digestion better, we need to understand the nitty-gritty of digestion.

What is the digestive system and what organs make it up? Digestion is the act of consuming food, breaking down food, processing, and utilizing it for energy. There are a couple ways food is digestion, one by mechanical digestion (think of when you chew your food where it’s physically being broken up into tiny little pieces); secondly by chemical digestion where food is broken down into even smaller molecules with the help of digestive enzymes. Hooray for enzymes! Enzymes actually start at the first site of digestion, our mouth, with saliva. Saliva contains an enzyme called Amylase which helps start the chemical process of breaking down the food while our teeth start the mechanical. I’m going to stop us right here- this friends, is why chewing your food well is VITAL for good digestion. The quicker we eat, the larger food particles enter our stomachs, the more digestive enzymes and energy is required for our bodies to break the food down; so why not help optimize this at the first line and first step? Right!

Next, food goes through your esophagus then reaches our stomachs where chemical digestion, gastric juices, start to breakdown our food- mostly the gastric juice is made up of pepsin and hydrochloric acid. I know, acid in our gut sounds scary right, but it’s a good thing! Our bodies must have enough acid to help breakdown food and proteins in our digestive system; actually those who suffer from low HCL level can actually experience higher incidences of GERD or reflux issues. Fun fact, our bodies can secret about 2 liters of HCL a day! Our body is incredibly smart though, we have enough mucus lining out stomach to protect that same acid we need, from damaging our own organs- it’s genius! So, while we have acid working on breaking down the food, we also still have mechanical digestion happening through a process called peristalsis (perry-stall-sis) which makes the muscles in the stomach wall contract and release to mix up the food and enzymes. Here’s a little video about how it works. After the food has been chemically and mechanically broken down, which can vary in time depending on how much food you eat and the variety but around 1-2 hours, it goes into the small intestine. The small intestine again, breaks down the food and also is a time where many vital nutrients are absorbed, little finger-like projections called villi and microvilli provide a HUGE surface area for our bodies to absorb these molecules from food and get into our blood vessels of the intestinal wall. This is how awesome the small intestine is: it’s about 22 feet long and 1 inch in diameter, and the surface area is about the size of a 2700 square foot tennis court! This is possible because the small intestine not only has folds, but on those folds are villi, and on those little villi are microvilli. Layers on layers on layers all to help you absorb food.

Our liver and pancreas get in on a little digestion action too- the liver produces bile, which is carried into the small intestine by a bile duct, then the pancreas secretes pancreatic juices and enzymes that aid in digestion as well. Lastly, after the food has been broken down and passed through the small intestine, the large intestine absorbs all remaining nutrients and mostly water; this is how stool is formed and then it passes out of our bodies.

  1. Carbohydrates: require amylase enzymes — broken down into simple sugars, glucose molecules
  2. Fats: require lipase enzymes — broken down into monoglycerides and fatty acids that involve emulsification, micelles, and chylomicrons
  3. Proteins: require pepsin enzymes — broken down into amino acids


I’m a visual learner and have a hunch many of you would enjoy “seeing” digestion in full action, so here’s an easy-to-navigate iconographic below to help you visualize how it all works, above. Basically the route of digestion is: mouth → esophagus → stomach → small intestine (pancreas and gallbladder are involved here as well) → large intestine → colon

There’s a saying I always teach and also practice myself as much as possible “Chew your liquids and swallow your solids”; meaning chew your food thoroughly enough that it’s to a puree texture and then swallow and swish around liquids in your mouth so you’re not just guzzling smoothies, juices, even water without activating the first part of digestion in the mouth from your saliva. Now that you understand both mechanical and chemical digestion with digestive enzymes, this makes sense, right?! I say this often to clients, you could eat the healthiest diet, have everything in your health “aligned”, yet if your digestive system is under stress and isn’t functioning properly- unfortunately you won’t be able to utilize and get the optimal/most out of what you just ate. So how do you optimize your digestion? It takes a lot of time, patience, and playing guinea pig to get to the bottom of exactly how your digestive system is, what helps and what “hurts’ it + some specific protocol I share with my clients. I’ll be sharing some of the tips in part II or if you have immediate questions you can always contact me for a consult here and we’ll get started.


Do I need to take digestive enzymes? 


Digestive enzymes in the form of a supplement can be quite helpful for those of you who need a little boost. For example, many can’t digest beans and legumes very well and there are many supplements on the market that help break down polysaccharides. Fun fact, there are some foods that contain natural digestive enzymes that are more “powerful” than most other whole foods like pineapple and papaya! Do you need to take digestive enzymes, no; but some cases it can help alleviate gas and bloating. Always check with your doc.

Other ‘Basics’ you may enjoy reading and learning about:

Part II will cover ways to improve your digestion, how to eliminate foods that irritate your stomach/digestive system, and any other questions that you all leave in the comment section below!
xx McKel

Resources: good ole’ textbooks from school or otherwise linked.

Share your thoughts

  • So informative! Thanks for sharing all the info, I’m always learning more and more about digestion and I think it’s so fascinating as well as crucial for us all to know about!

  • Rebeca

    Love, love this series. So much great information presented easily – you rock, McKel!
    I had a question related to antibiotics but I think I have my answer after reading your ‘Guide to Probiotics’. I’m taking antibiotics (hello, sinus infection from hell!) and, besides probiotic rich foods, I’m taking a supplement to help things get back on track.

    Looking forward to part II!

  • Zoe Davies

    This was really interesting, thank you! Looking forward to part 2! 🙂

  • You are a nutrition rockstar, Mckel! I’m so fascinated by digestion, and I feel it is SO important to our overall health. I would love to hear more about digestive friendly/digestive hampering foods + your input on small intestinal bacterial overgrowth (SIBO) and other issues that can go out of whack in the digestive system.

    • Great question Kate! I’ll address that in part II as well- glad I’m not the only one who’s fascinated by digestion!

  • A

    I’ve been having digestive problems for over a year – my diet is extremely rich in fiber – I consume lots of almonds but I can’t and won’t give up on them. I believe I have a leaky gut; my hair has fallen out (for a year) and is now very thin and I don’t think I’m getting all the nutrients. This started with my decision to cut out junk food and eat whole foods.
    I honestly need help. Nothing is helping. I would appreciate it if you could answer via email instead of the comment section but of course that’s up to you. Have a nice day!

  • Della

    I look forward to reading the next part of this. I am 5 weeks in to a vegetarian change and was borderline ready to quit the other day – So bloated and well – windy!! ! I’ve resolved to eliminate legumes and wheat for now just so I can see what is going on. Will wlso chew slower!

    • Great question Della, will bring this up in part II and also like you said, chewing slower may kick start it!

  • Ali

    What a great post! I’m looking forward to reading your tips in Part II. I was wondering if you could address dietary changes and/or supplements that are beneficial for constipation and bloating. I have IBS with constipation and have found that increasing my fiber and water intake helps somewhat, but I would love to hear your take on other things to try! Thanks so much!

  • Mercy

    Hi! I love all your stuff and really enjoyed this post! I recently started learning about digestion because I was diagnosed with acid reflux. It’s definetly fascinating! I guess my question would be…… How do you know if you have good/bad digestion? Thanks for all you recipes and posts!!!

    • Hi Mercy- great question and a loaded question at that, but I suppose bad digestion can be as obvious as it impacting your daily life or as subtle as bloating and gas OR trying a new way of eating and finding yourself with extra energy and even “better” digestion – feel free to sign up for a consult with me, I’d be happy to go more in depth with you.

  • Michelle

    I loved learning this in my nutrition class, and loved relearning it all reading this post! Can’t wait for part 2!!
    (and can you actually write a post on stress and digestion? that sounds really interesting)

  • Trista

    I understand how stress can effect digestion. My question is: are there any foods you recommend eating (or not eating) when you are going through a stressful time? For instance, during a transitional period like back-to-school, I know I am more stressed out. I try to manage my stress, but I also know that it is somewhat inevitable and things will settle down once the transitional period passes. What kinds of things can I do with my diet to help my digestion during that stressful time?

    • Hi Trista- excellent question and I’ll be answering this in part II more in depth, but in a nutshell try foods that are easy on YOUR system. If that’s more raw food then great, or if it’s more soft cooked veggies and grains that’s great too- it’s all about listening in to how your body works and honoring that 🙂

  • Awesome post 🙂 Digestion is such a complex topic and you present the information in such a great way! Looking forward to reading part 2!

  • Katie

    Thanks so much for this, McKel! I’m on my last semester of my dietetics degree and I have my first test on The Cell and Digestion on Wednesday and I really needed a visual and simplified version so I could picture digestion from start to finish! You’re the best 🙂 -Katie

  • John

    Very interesting article. Thanks for making it easy for us to understand. I have a question in regards to gall bladder malabsorption. Anything that you recommend doing when suffering from this? (Any special vitamin intake?). They seem to recommend a low fat diet but I find it difficult to do when trying to have an active / sport life (high on proteins)

    • Excellent question, John. I’ll make note to answer that in part II! In a nutshell, you may want to look into a digestive enzyme but check with your MD. first

  • McKel, please do write an entire blog post about how stress affects our digestion! I would really appreciate it!

  • elizabeth

    Would you please send me part II basics on digestion that you mention in your article as indicated below:

    Part II will cover ways to improve your digestion, how to eliminate foods that irritate your stomach/digestive system, and any other questions that you all leave in the comment section below!

    Thank you

    • We haven’t covered part II yet! Be sure to sign up for my newsletter, you’ll know the first thing when it launches 🙂

  • Fitness Dietitian Em

    A fellow RD.. woohoo 🙂

    Very informative!

  • Meaghan

    Love this post! You have done a great job of making it easy to understand. I’ve struggled with digestion issues for some time now and trying really hard to get them in check so thank you for your help!

    Love the water color of the stomach. Is it available to download on your site somewhere? Would be a great reminder to always show your guts some love. 🙂

    • McKel Hill

      So glad this was helpful Meaghan! All my watercolors will be turned into prints available for download in the NS shop early next year so be on the look out! xx M


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