Digestive Enzymes: Types and Function

What are Digestive Enzymes, and What Do They Do?

Digestive enzymes are specialised proteins secreted by the gastrointestinal system that help catalyse the breakdown of the food we eat into smaller components easily absorbed by our body [1]. Our food contains complex macronutrients (carbohydrates, proteins, fats) and other micronutrients that fuel our daily tasks. The digestive enzymes play a crucial role in enabling our bodies to effectively absorb these nutrients from the complex food we consume.

Different digestive enzymes are secreted by various organs and glands in the digestive system, including:

• Salivary glands in the mouth
• Stomach
• Pancreas
• Small intestine

The enzyme types secreted by these organs work together to ensure that our food is processed into simpler compounds, such as amino acids, simple sugars (monosaccharides), and fatty acids, allowing our body to extract the maximum nutrients [2].

In a healthy human being, the production and secretion of enzymes in the digestive system are regulated by various hormones and other signals. These work in coordination to ensure that the right amount of each enzyme is synthesised and released at the right time.

What Causes Insufficient Secretion of Digestive Enzymes?

When the pancreas cannot synthesise sufficient digestive enzymes to digest food properly, this condition is called Exocrine Pancreatic Insufficiency (EPI) [3]. When the salivary glands in the mouth cannot secrete enough digestive enzymes, this condition is called hyposalivation (dry mouth). In the stomach, Hypochlorhydria or low stomach acid impairs the activation of pepsin, a gastric enzyme, and can hinder overall digestion [4].

These conditions occur due to a variety of factors, including:

• Ageing (as digestive enzyme production can naturally decline with age) [5]
• Injury
• Medications, including proton pump inhibitors (PPIs) and H2 receptor blockers, which can reduce stomach acid
• Alcohol consumption
• Certain medical conditions, such as Sjögren’s syndrome (affecting salivary glands), Cystic Fibrosis, Shwachman-Diamond Syndrome, and chronic pancreatitis or pancreatic cancer [3]
• Surgical removal of the pancreas
• Other factors that lead to insufficient levels of digestive enzyme types include:
• People with gastrointestinal disorders, such as irritable bowel syndrome (IBS), Crohn’s disease, or ulcerative colitis (though the link is complex and symptoms often overlap) [6].

What Are the Symptoms of Digestive Enzyme Insufficiency?

The lack of digestive enzymes leads to various complications, primarily due to maldigestion and malabsorption [7]. Symptoms can include:

• Persistent gastrointestinal discomfort
• Bloating and excessive gas
• Abdominal pain and cramping
• Chronic diarrhoea or constipation
• Foul-smelling, fatty stools (steatorrhea)
• Unintended weight loss
• Signs of nutrient deficiency (e.g., fatigue, weakened immunity)
• In severe cases related to the pancreas, Pancreatitis can occur
• If you are experiencing these symptoms frequently, your body might not be producing enough digestive enzymes. It is essential to consult your doctor for proper evaluation and management to rule out underlying medical conditions [7].

What Are the Various Types of Digestive Enzymes?

There are different types of enzymes in the digestive system, each designed to break down a specific macronutrient. These enzymes are classified as follows:

1. Amylases

• Amylase is the digestive enzyme secreted by salivary glands and the pancreas. It helps break down complex carbohydrates (starch and glycogen) into smaller sugars [1].
• There are two major types of amylase found in our bodies:
• Salivary Amylase (Ptyalin): Secreted by the salivary glands in the mouth, it starts carbohydrate digestion. It breaks down starch into dextrins and maltose (a disaccharide) [8].
• Pancreatic Amylase: Secreted by the pancreas into the small intestine, which continues the breakdown of starch into maltose.
• The deficiency of amylase can lead to carbohydrate malabsorption, causing intestinal gas and diarrhoea.

2. Proteases

• Proteases, also called peptidases, are digestive enzymes secreted by the pancreas and stomach. These help break down proteins into smaller peptides and individual amino acids to be absorbed by the body [2].
• Key proteases involved in digestion include:
• Pepsin: An aspartic protease in the stomach. It is secreted as an inactive precursor (pepsinogen) by chief cells and activated by gastric acid. It begins the breakdown of proteins into smaller peptides [9].
• Trypsin and Chymotrypsin: Serine proteases secreted by the pancreas into the small intestine. They cleave complex protein chains at specific sites to generate amino acids and smaller peptides [2].
• Elastase: Another pancreatic protease that breaks down the protein elastin.
• Carboxypeptidase A and B: Exopeptidases that cleave amino acids from the carboxyl end of the peptide chain.

3. Lipases

• Lipases are the digestive enzymes secreted by the pancreas and gastric mucosa. They help break down dietary triglycerides (fats and oils) into fatty acids and glycerol, which are easily absorbed by the body [10].
• The lipases involved in digestion include:
• Gastric Lipase: Secreted by the stomach and responsible for the initial breakdown of short and medium-chain fatty acids (up to 30% of fat digestion) [10].
• Pancreatic Lipase: Secreted by the pancreas into the small intestine. It is the primary enzyme for fat digestion, breaking down complex triglycerides into simpler monoglycerides and fatty acids that are absorbed by the small intestine [10].

4. Lactase

Lactase is the digestive enzyme secreted by the lining of the small intestine (brush border). It helps break down lactose or milk sugar into absorbable simple sugars (monosaccharides) such as glucose and galactose [11]. The deficiency of lactase in the small intestine causes lactose intolerance, a common condition where the body cannot digest milk sugar.

5. Maltase

Maltase is the digestive enzyme secreted by the brush border of the small intestine. It helps break down maltose (a disaccharide) into two molecules of glucose, which is easily absorbed by our bodies.

6. Sucrase

Sucrase is the digestive enzyme secreted by the brush border of the small intestine. It helps break down sucrose (table sugar) into the simple sugars glucose and fructose that are easily absorbed by our bodies.

How to Treat Digestive Enzyme Insufficiency?

The primary approach to treating insufficiency of enzymes in the digestive system is to address the underlying cause. In cases where the cause is a medical condition, the following methods are often employed:

1. Digestive Enzyme Supplements

Supplements are available over the counter and by prescription to help manage the symptoms of bloating, acid reflux, and diarrhoea associated with mild to moderate insufficiency. These are available in the form of powder, oral capsules, or tablets that are taken with meals. These supplements help break down carbohydrates, proteins, and fats, making them easier to absorb.

For those with severe medical conditions, such as cystic fibrosis, chronic pancreatitis, and severe pancreatic insufficiency, Pancreatic Enzyme Replacement Therapy (PERT) is effective [3]. PERT involves taking prescription-strength oral supplements with each meal and snack, as guided by a doctor, to ensure food is digested effectively.

Note: Always consult a doctor or a registered dietitian before taking any of these supplements. Only your healthcare providers can properly diagnose the type and severity of enzyme deficiency and guide you on the appropriate management plan.

2. Dietary Modifications and Natural Sources

Specific foods are naturally rich in digestive enzymes, which can support the digestive process [13]. Incorporating these foods into your diet may promote digestion and better nutrient absorption:

• Pineapples (Bromelain)
• Papayas (Papain)
• Mangoes (Amylase)
• Avocados (Lipase)
• Fermented foods (Kefir, Sauerkraut, Kimchi)
• Raw honey

3. Surgery

In rare and severe cases of underlying conditions (e.g., chronic pancreatitis), surgical procedures may be considered by specialists. For example, in cases of severe, chronic pancreatitis, a total pancreatectomy (removal of the pancreas) may be performed, which is always followed by lifelong PERT to help the body digest food [3]. In some cases, small bowel transplantations can be performed to treat very specific and rare enzyme deficiencies.

Conclusion

Digestive enzymes are vital for nutrient absorption. If you experience persistent and debilitating symptoms such as dehydration, malnutrition, weakness, bloating, foul-smelling stools (steatorrhea), abdominal pain, diarrhoea, and unintended weight loss, it indicates a potential issue with your digestive system [7]. Incorporating naturally enzyme-rich foods may help with minor issues, but it is crucial to seek prompt medical advice for proper diagnosis and treatment of underlying enzyme insufficiency.

Frequently Asked Questions (FAQs)

When should I take digestive enzymes?

The timing depends on the specific product and your individual needs, as advised by your doctor. Generally, if you have difficulty digesting certain foods, you may take them just before or with meals. For those on Pancreatic Enzyme Replacement Therapy (PERT), capsules are typically taken with every meal and snack to ensure the enzymes mix properly with the food [3].

Who should take digestive enzyme supplements?

Digestive enzyme supplements are primarily recommended for individuals with medically diagnosed conditions leading to Exocrine Pancreatic Insufficiency (EPI), such as Cystic Fibrosis, Chronic Pancreatitis, and post-pancreatic surgery [3]. They may also be recommended by a physician for older adults with weak digestion or individuals with specific enzyme deficiencies like lactase deficiency (lactose intolerance).

What happens when the body doesn’t secrete enough digestive enzymes?

When the body doesn’t secrete enough digestive enzymes, the consequence is maldigestion and malabsorption. This can lead to nutritional deficiencies, gastrointestinal problems (gas, bloating, pain, diarrhoea), unintended weight loss, and in severe, untreated cases, complications like Pancreatitis [7].

How to increase digestive enzymes naturally?

Specific foods rich in digestive enzymes include Pineapples (Bromelain), Papayas (Papain), Mangoes, raw honey, Bananas, Avocados, Kefir, Sauerkraut, Kimchi, and Kiwi fruit. Incorporating a diverse range of these whole, enzyme-rich foods into your diet promotes overall digestion and better nutrient absorption [13].

Are there any side effects of having a digestive enzyme supplement?

Digestive enzyme supplements are generally safe when taken as directed. However, some people can experience mild gastrointestinal side effects, such as diarrhoea, abdominal pain, cramps, or nausea [14]. It is essential to use these supplements under medical supervision to ensure correct dosing and to rule out serious underlying causes for your symptoms.

References

[1] Pandol, S. J. (2010). Digestive Enzymes. In Molecular Mechanisms in the Pathogenesis of Chronic Pancreatitis. Morgan & Claypool Life Sciences. Available from https://www.ncbi.nlm.nih.gov/books/NBK54127/

[2] López-Otín, C., & Bond, J. S. (2008). Proteases: Multifunctional Enzymes in Life and Disease. Journal of Biological Chemistry, 283(45), 30433–30437. https://doi.org/10.1074/jbc.r800035200

[3] Garg, P. K., & Khajuria, V. (2020). Pancreatic enzyme replacement therapy in exocrine pancreatic insufficiency. World Journal of Gastroenterology, 26(34), 5124–5141. https://doi.org/10.3748/wjg.v26.i34.5124

[4] Saltzman, J. R., & Russell, R. M. (1995). The aging gut. Nutritional consequences. Clinics in Geriatric Medicine, 11(4), 687–704. https://doi.org/10.1016/s0749-0690(18)30282-3

[5] Shi, Y., & Li, H. (2022). Influence of aging on the digestive system. Aging and Disease, 13(1), 164–173. https://doi.org/10.14336/AD.2021.0620

[6] Keller, J., & Layer, P. (2014). The Pathophysiology of Malabsorption. Visceral Medicine, 30(3), 150–154. https://doi.org/10.1159/000363242

[7] Singh, R., & Sarmah, D. (2023). Malnutrition. StatPearls Publishing. Available from https://www.ncbi.nlm.nih.gov/books/NBK560871/

[8] Akinfemiwa, O., Muniraj, T., & Zubair, M. (2023). Amylase. StatPearls. StatPearls Publishing. Available from https://www.ncbi.nlm.nih.gov/books/NBK557738/

[9] Shade, K. (2017). The Role of Stomach Acid in the Digestion of Protein. Journal of Sports Science and Medicine, 16(4), 438–445. Available from https://www.jssm.org/vol16/n4/22/v16n4-22text.php

[10] Li, J., & Li, R. (2019). Mechanisms of Lipase Secretion and Action. Comprehensive Reviews in Food Science and Food Safety, 18(4), 1085–1102. https://doi.org/10.1111/1541-4337.12450

[11] Di Rienzo, T., D’Angelo, G., & D’Aversa, A. (2013). Lactose intolerance: from diagnosis to therapeutic options. European Review for Medical and Pharmacological Sciences, 17(suppl 2), 18-25. Available from https://pubmed.ncbi.nlm.nih.gov/24443063/

[12] Cohen, S. A. (2019). Congenital Sucrase-Isomaltase Deficiency: Genetic Variants and Contemporary Management. Journal of Pediatric Gastroenterology and Nutrition, 68(6), 770–775. https://doi.org/10.1097/MPG.0000000000002347

[13] Ianiro, G., Pecere, S., & Pompili, M. (2016). Digestive Enzyme Supplementation in Gastrointestinal Diseases. Current Drug Metabolism, 17(2), 187-193. https://doi.org/10.2174/138920021702160205112227

[14] Ullah, H., Di Minno, A., Piccinocchi, R., et al. (2023). Efficacy of digestive enzyme supplementation in functional dyspepsia: A monocentric, randomised, double-blind, placebo-controlled, clinical trial. Biomedicine & Pharmacotherapy, 169, 115858. https://doi.org/10.1016/j.biopha.2023.115858