5 Stages of Digestion
If you’re struggling with fatigue, brain fog, or getting the fitness results you want, you need to troubleshoot your digestive health. Most people have suboptimal digestion and don’t even know what having a healthy digestive system feels like. Matt and Wade personally experienced this themselves back in the 90s. They thought they were already in…
If you’re struggling with fatigue, brain fog, or getting the fitness results you want, you need to troubleshoot your digestive health. Most people have suboptimal digestion and don’t even know what having a healthy digestive system feels like.
Matt and Wade personally experienced this themselves back in the 90s. They thought they were already in tip-top shape, but when they optimized their digestion and tried high-doses of enzymes for 90 days, they gained muscle, lost fat, and experienced massive health improvements. Wade went on to compete in Mr. Universe and Mr. Olympia on a plant-based diet and 85 grams/day of protein, while his competitors needed 250 grams/day!
They also saw many clients who trained hard, ate well, and supplemented. But they didn’t achieve their full potential until they optimized their digestion, grew the right gut bacteria, and increased absorption.
You’re not what you eat, but what you absorb. In order to optimize your health, it’s important to understand the five phases of digestion and how they impact your eventual absorption.
Phase 1: Anticipation
The smell of food makes you salivate and your stomach grows, because your brain is intimately involved with your digestion as much as your gut is. In fact, in order to optimize your digestion, you need to learn how to fully relax in “rest and digest” mode and be mentally engaged with your food.
Studies based on fMRI, which maps function to brain regions based on oxygen consumption, saw that parts of the brain lit up as subjects saw or smell food1. Our brains associate certain flavors with certain nutrition and caloric density of the food. Delicious and calorie-dense foods usually trigger a big dopamine release, which makes you feel rewarded.
The sight and sensation of food also trigger saliva, stomach acid, and digestive enzyme secretions2, 3. These processes happen through the “rest and digest” neurons called the vagus nerve. This is one of the most important neurons for the health and gut-brain communications3.
Chewing serves many important functions.
First, it grinds foods into smaller pieces, making it easier for digestive enzymes to access the food later on in the digestive process.
Second, it mixes the food with saliva, so you can taste the food. Saliva lubricates and binds food into a bolus, so you can safely swallow it4. The saliva also contains white blood cells, antibodies, and lysozyme (a bacteria-digesting enzyme), which kill pathogens that could be in your food5.
Third, chewing stimulates stomach acid and digestive enzymes secretions throughout the digestive tract6. Typically saliva only serves as a lubricant and contains minimal digestive enzymes. But once chewing commences, the salivary glands release digestive enzymes, such as salivary amylase (starch-digesting) and lipase (fat-digesting). In sham feeding studies, chewing food (and spitting them out) was enough to trigger the pancreas to release 50% of total digestive enzymes it would secrete in a meal7.
Fourth, chewing stimulates the vagus nerve, which not only reduces inflammation throughout your body but also helps you relax. So that further stages of digestive function can function optimally8.
It is, therefore, important to take the time to properly chew your food. Rushing your meals and not chewing thoroughly can result in discomfort, indigestion, and perhaps even acid reflux.
Phase 3: Stomach
The stomach is where most of the food breakdown starts. It secretes stomach acid, digestive enzymes, and moves to mix food with the acid and enzymes9.
The stomach acid plays many important roles, including9:
- Signaling the valve between the esophagus and stomach to close, preventing acid reflux
- Preventing infections by killing most microorganisms and parasites
- Activating pepsin, a key protein-digesting enzyme in the stomach
- Loosening up the molecular structure of the foods, allowing easier access to enzymes
- Freeing up minerals such as calcium, magnesium, and iron into absorbable forms
- Freeing up vitamin B12 to mix with intrinsic factor to be absorbed in the large intestine
- When the food travels from the stomach to the small intestine, the acidity of the bolus activates further stages of digestion
Low stomach acid will create an unhealthy ripple effect throughout the body, including reduced appetite, increased risk of gut infections, and deficiencies in mineral, protein and vitamin B12. These tend to happen in the elderly, those under a lot of stress, and those with weak vagus nerves. Small intestine bacterial overgrowth may also occur due to reduced peristalsis, resulting in gas, bloating, and potentially diarrhea or constipation.
Fortunately, taking a betaine HCL supplement, such as HCL Breakthrough, maybe one of the easiest and affordable tips to improve your digestive function.
Phase 4: Small intestine
Once the food reaches the small intestine, your anticipation would have already triggered 50% of the digestive juices. The acidity of the food bolus will trigger the remainder of it. The small intestine is where most of the digestion occurs, including the secretion of:
- Bile to help emulsify fats into smaller droplets, allowing lipase to digest the fat molecules.
- Pancreatic amylase to digest starches.
- Protein-digesting pro-enzymes, which are then activated in the small intestines to digest proteins.
- Sugar-digesting enzymes, such as sucrase, maltase, and lactase to digest sucrose (table sugar), maltose (sugars with two glucose molecules), and lactose (milk sugar), respectively.
Peristalsis moves the food bolus along as the food gets digested and absorbed. Nutrient absorption also depends on the integrity of the mucosal barrier, the single-cell lining of the gut, and villi structure, finger-like structures that maximize the absorptive surface. The mucosal barrier and villi structure are often compromised in untreated celiac disease, inflammatory bowel disease, gut infections, and other sources of gut inflammation 10-12.
Incomplete digestion can result in partially digested peptides, carbohydrates, and fats. Peptide and carbohydrates may get fermented by the gut bacteria in the large intestine, whereas the fat tends to get excreted as fat in the stool. Protein fermentation may create metabolites such as hydrogen sulfides, ammonia, and phenol. Which smell bad and contribute to colon cancers and ulcerative colitis.13
Incompletely digested proteins are the most dangerous because partially digested peptides may cause inflammation and interfere with other bodily functions14,15. In individuals with genetic susceptibility, antibodies against gliadin, and a partially digested peptide of gluten, may contribute to autoimmunity or autism16. Beta-casomorphin-7, a partially digested peptide of A1 milk, can cause gut inflammation17.
Therefore, one of the most important steps to fixing chronic inflammation is to ensure that your protein digestion is optimal. Most people with chronic inflammation also have reduced stomach acid and enzymes, so supplementation is often beneficial. Proteases are the most expensive ingredient of any digestive enzyme products, so many manufacturers cut corners on them. MassZymes has the highest dose of active protease on the market, which can help ensure that you absorb all the nutrients your body needs and reduce inflammation from incomplete digestion.
Phase 5: Large intestine and elimination
Here, most of the digestive functions are complete. The large intestine is where most of the water, electrolytes, and vitamin B12 are absorbed. In addition, this is where your gut microorganisms take the stage.
To learn more about gut bacteria and digestive health, and how to optimize your gut bacteria with probiotics supplements, check out this article.
- Dagher, A. Functional brain imaging of appetite. Trends in Endocrinology and Metabolism vol. 23 250–260 (2012).
- Pedersen, A. M., Bardow, A., Jensen, S. B. & Nauntofte, B. Saliva and gastrointestinal functions of taste, mastication, swallowing and digestion. Oral Diseases vol. 8 117–129 (2002).
- Katschinski, M. Nutritional implications of cephalic phase gastrointestinal responses. in Appetite vol. 34 189–196 (Academic Press, 2000).
- Tiwari, M. Science behind human saliva. Journal of Natural Science, Biology and Medicine vol. 2 53–58 (2011).
- Fábián, T. K., Hermann, P., Beck, A., Fejérdy, P. & Fábián, G. Salivary defense proteins: Their network and role in innate and acquired oral immunity. International Journal of Molecular Sciences vol. 13 4295–4320 (2012).
- Lashley, K. S. Reflex secretion of the human parotid gland. J. Exp. Psychol. 1, 461–493 (1916).
- Anagnostides, A., Chadwick, V. S., Selden, A. C. & Maton, P. N. Sham feeding and pancreatic secretion. Evidence for direct vagal stimulation of enzyme output. Gastroenterology 87, 109–14 (1984).
- By gum, it might be good for you – Harvard Health. (2006) //www.health.harvard.edu/newsletter_article/By_gum_it_might_be_good_for_you Date accessed: 03/27/2020.
- Keller, J. & Layer, P. The pathophysiology of malabsorption. Viszeralmedizin: Gastrointestinal Medicine and Surgery vol. 30 150–154 (2014).
- Stein, J. & Schuppan, D. Coeliac disease-new pathophysiological findings and their implications for therapy. Viszeralmedizin: Gastrointestinal Medicine and Surgery vol. 30 156–165 (2014).
- Blander, J. M. Death in the intestinal epithelium—basic biology and implications for inflammatory bowel disease. FEBS Journal vol. 283 2720–2730 (2016).
- De Medina, F. S., Romero-Calvo, I., Mascaraque, C. & Martínez-Augustin, O. Intestinal inflammation and mucosal barrier function. Inflammatory Bowel Diseases vol. 20 2394–2404 (2014).
- Evenepoel, P. et al. Evidence for impaired assimilation and increased colonic fermentation of protein, related to gastric acid suppression therapy. Aliment. Pharmacol. Ther. 12, 1011–1019 (1998).
- Chakrabarti, S., Jahandideh, F. & Wu, J. Food-Derived Bioactive Peptides on Inflammation and Oxidative Stress. Biomed Res. Int. 2014, (2014).
- de Punder, K. & Pruimboom, L. The dietary intake of wheat and other cereal grains and their role in inflammation. Nutrients vol. 5 771–787 (2013).
- Vojdani, A. et al. Heat shock protein and gliadin peptide promote development of peptidase antibodies in children with autism and patients with autoimmune disease. Clin. Diagn. Lab. Immunol. 11, 515–524 (2004).
- Brooke-Taylor, S., Dwyer, K., Woodford, K. & Kost, N. Systematic Review of the Gastrointestinal Effects of A1 Compared with A2 β-Casein. Adv. Nutr. An Int. Rev. J. 8, 739–748 (2017).