Digestive Enzymes: Types and Function
What Are Digestive Enzymes?
Digestive enzymes are released when we:
- Anticipate eating
- Smell and taste food
- Go through the digestive process
Some foods require certain digestive enzymes to break down the specific nutrients they contain.
A variety of health conditions, especially those that affect the pancreas, can lead to deficiencies in digestive enzymes. This is because the pancreas secretes several key enzymes.
Often these deficiencies can be fixed by changing your diet. You can avoid certain foods or eat foods containing naturally occurring digestive enzymes. You can also take prescription or over-the-counter (OTC) enzyme supplements.
Types of Digestive Enzymes
Each of the many different digestive enzymes targets a specific nutrient and splits it up into a form that can eventually be absorbed.
The most important digestive enzymes are:
Amylase is important for digesting carbohydrates. It breaks down starches into sugars.
Amylase is secreted by both the salivary glands and the pancreas. The measurement of amylase levels in the blood is sometimes used as an aid in diagnosing various pancreas or other digestive tract diseases.
High levels of amylase in the blood may mean you have:
- A blocked or injured duct of the pancreas
- Pancreatic cancer
- Acute pancreatitis, which is a sudden inflammation of the pancreas2
Low levels of amylase may mean you have chronic pancreatitis (ongoing inflammation of the pancreas) or liver disease.
The small intestine releases maltase, which is responsible for breaking down maltose (malt sugar) into glucose (simple sugar). The body uses glucose for energy.
During digestion, starch is partially transformed into maltose by amylases. The maltase enzyme then changes maltose into glucose. This sugar is then either used immediately by the body or stored in the liver as glycogen for future use.
Lactase (also called lactase-phlorizin hydrolase) is an enzyme that breaks down lactose, a sugar found in dairy products. It turns lactose into the simple sugars glucose and galactose.
Lactase is produced by cells known as enterocytes that line the intestinal tract. Lactose that is not absorbed is fermented by bacteria in the gut. This can cause you to have gas and an upset stomach.3
Lipase is responsible for the breakdown of fats into fatty acids and glycerol (simple sugar alcohol). It’s produced in small amounts by your mouth and stomach, and in larger amounts by your pancreas.
Also called peptidases, proteolytic enzymes, or proteinases, these digestive enzymes break down proteins into amino acids. They also play a role in numerous body processes, including:
- Cell division
- Blood clotting
- Immune function4
Proteases are produced in the stomach and pancreas. The main ones are:
- Pepsin: Pepsin is secreted by the stomach to break down proteins into peptides, or smaller groupings of amino acids. Those amino acids are then either absorbed or broken down further in the small intestine.
- Trypsin: Trypsin forms when an enzyme secreted by the pancreas is activated by an enzyme in the small intestine. Trypsin then activates additional pancreatic enzymes, such as carboxypeptidase and chymotrypsin, to help break down peptides.
- Chymotrypsin: This enzyme breaks down peptides into free amino acids that can be absorbed by the intestinal wall.
- Carboxypeptidase A: Secreted by the pancreas, it splits peptides into individual amino acids.
- Carboxypeptidase B: Secreted by the pancreas, it breaks down basic amino acids.
Sucrase is secreted by the small intestine, where it breaks down sucrose (the sugar in table sugar) into fructose and glucose. These are simpler sugars that the body can absorb.
Sucrase is found along the intestinal villi. These are tiny hair-like structures that line the intestine and absorb nutrients into the bloodstream.
Digestive Enzyme Deficiencies
There are a variety of health conditions that can interfere with the secretion of enough digestive enzymes to fully digest foods. Some are inherited genetic conditions while others develop over time.
Lactose intolerance occurs when you aren’t able to digest lactose because of insufficient production of lactase by the small intestine. When you consume dairy products, you may experience:
- Abdominal pain
There are several forms of lactose intolerance.
Congenital Lactase Deficiency
Congenital lactase deficiency (also called congenital alactasia) is a rare inherited form of lactose intolerance. It happens when newborns are unable to break down lactose in breast milk or formula. They get severe diarrhea if they aren’t given a lactose-free alternative.
Congenital lactase deficiency is caused by mutations in the LCT gene that provides instructions for making the lactase enzyme.5
Lactase non-persistence is a common type of lactose intolerance that some people develop as adults. It affects around 65% of people, and it’s caused by decreased expression (activity) of the LCT gene. Symptoms typically begin 30 minutes to two hours after eating or drinking dairy.3
Most people with lactase non-persistence keep some level of lactase activity and can continue to include a small amount of lactose in their diets. This may be in the form of cheese or yogurt since both tend to be tolerated better than fresh milk.
Secondary Lactose Intolerance
Secondary lactose intolerance develops when lactase production is reduced because of diseases that can damage the small intestine. These diseases include celiac disease or Crohn’s disease as well as other illnesses or injuries that affect the intestinal wall.
Exocrine Pancreatic Insufficiency
The pancreas produces the key digestive enzymes amylase, protease, and lipase. People with exocrine pancreatic insufficiency (EPI) have a deficiency of these enzymes. As a result, they are unable to digest food properly, especially fats.
The health conditions that affect the pancreas and are associated with EPI are:
- Chronic pancreatitis: An inflammation of the pancreas that can permanently damage the organ over time
- Cystic fibrosis: An inherited genetic condition that causes severe damage to the lungs and digestive system, including the pancreas6
- Pancreatic cancer
Foods High in Digestive Enzymes
A variety of foods, especially tropical fruits and fermented vegetables, are naturally high in digestive enzymes that might speed up the digestion of certain nutrients.
It’s best to eat them raw since heat can lessen or destroy these plant enzymes.