The Key Enzyme Used to Break Down Dairy: A Guide to Lactase

December 12, 2025 •

3 min read

According to the National Institutes of Health, an estimated 68% of the world's population has some degree of lactose malabsorption. This widespread condition highlights the importance of understanding what enzyme is used to break down dairy: lactase. This article explores how this critical enzyme functions, what happens when it's deficient, and how to manage its effects on your diet.

Quick Summary

This article explains the function of lactase, the digestive enzyme that breaks down lactose in dairy products. It details how a deficiency leads to lactose intolerance and provides comprehensive information on symptoms, causes, management strategies, and supplement options for better digestive health.

Key Points

Lactase: The enzyme that breaks down lactose, the sugar found in dairy products, is called lactase.
Digestion Process: In the small intestine, lactase breaks lactose down into simpler, absorbable sugars called glucose and galactose.
Lactose Intolerance Cause: When lactase is deficient, undigested lactose moves to the large intestine, where bacteria ferment it, causing gas, bloating, and diarrhea.
Lactase Supplements: Over-the-counter lactase enzyme supplements can be taken just before consuming dairy to help with digestion and prevent symptoms.
Management: Managing lactose intolerance involves controlling dietary intake, choosing low-lactose products like hard cheeses, and using supplements.
Types of Deficiency: Lactase deficiency can be primary (age-related), secondary (from illness), congenital (from birth), or developmental (in premature infants).

What is the Enzyme Used to Break Down Dairy?

The enzyme responsible for breaking down the sugar found in dairy products is called lactase. In healthy individuals, the small intestine produces this enzyme, specifically in the brush border lining the intestinal wall. Lactase's primary function is to break down lactose, a complex sugar (disaccharide), into two simpler sugars: glucose and galactose. These simple sugars are then easily absorbed into the bloodstream, providing energy to the body.

The Process of Lactose Digestion

When you consume milk or other dairy products, the lactose travels to your small intestine. Here, lactase acts as a catalyst, splitting the lactose molecule into glucose and galactose. This enzymatic process ensures that the body can efficiently absorb and utilize the sugar, a seamless part of normal digestion for those with sufficient lactase production.

What Happens During Lactose Intolerance?

Lactose intolerance is the result of insufficient lactase production in the small intestine. When this deficiency occurs, undigested lactose travels to the large intestine where it is fermented by natural bacteria. This bacterial activity produces various gases and fatty acids, leading to classic symptoms.

Common symptoms of lactose intolerance include:

Bloating and abdominal cramping
Excessive gas
Nausea
Diarrhea, caused by undigested lactose drawing water into the large intestine

The severity of symptoms depends on the amount of lactose consumed and the degree of lactase deficiency.

Four Types of Lactase Deficiency

Low lactase levels can stem from several causes, leading to four distinct types of deficiency:

Primary Lactase Deficiency: The most common type, where lactase production naturally declines after infancy, often genetically determined.
Secondary Lactase Deficiency: Occurs when the small intestine is damaged by conditions like celiac disease or gastroenteritis, temporarily reducing lactase production. Recovery of the underlying issue can restore lactase levels.
Congenital Lactase Deficiency: A rare genetic disorder where infants are born with almost no lactase. It requires lactose-free formula from birth.
Developmental Lactase Deficiency: A temporary condition in premature babies due to an underdeveloped small intestine, which typically resolves as they mature.

Managing Lactose Intolerance with Lactase

While there's no cure, lactose intolerance symptoms can be managed effectively. The main strategy involves controlling dietary lactose intake, often with the aid of lactase itself.

Strategies for management include:

Dietary Modification: Many individuals tolerate small amounts of lactose. Finding your personal tolerance level and eating dairy with other foods can help reduce symptoms.
Low-Lactose Products: Hard cheeses and yogurt with active cultures contain less lactose and are often well-tolerated.
Lactase Supplements: Over-the-counter supplements provide the missing enzyme. Taken before or with dairy, they can improve digestion.

Lactase vs. Other Digestive Enzymes

Understanding lactase is clearer when compared to other digestive enzymes:


Feature	Lactase Enzyme	Other Digestive Enzymes
Function	Specifically breaks down lactose (milk sugar).	Break down other food components, such as fats, proteins, or starches.
Target Nutrient	Lactose.	Fats (lipase), proteins (protease), carbohydrates (amylase).
Associated Condition	Lactose Intolerance.	General indigestion, malabsorption issues, or specific deficiencies unrelated to dairy.
Source	Produced in the small intestine or from yeasts/molds for supplements.	Produced in the pancreas, stomach, and salivary glands; supplements may derive from plant, animal, or microbial sources.
Supplement Use	Helps digest dairy specifically.	Aids overall digestion or targets other specific food sensitivities.

Conclusion

Lactase is the specific enzyme used to break down dairy by converting lactose into digestible glucose and galactose. A deficiency in lactase causes lactose intolerance and its uncomfortable symptoms. However, through dietary management, using lactase enzyme supplements, and understanding individual needs, managing lactose intolerance is achievable. Recognizing lactase's vital role allows for informed dietary choices and improved digestive comfort.

Frequently Asked Questions

If you are lactose intolerant and consume dairy, undigested lactose passes into your large intestine. Bacteria ferment this sugar, producing gases and other byproducts that cause bloating, cramping, gas, and diarrhea.

You cannot increase your body's natural production of lactase if you have primary or congenital lactose intolerance. However, secondary lactase deficiency may improve if the underlying illness or injury to the small intestine heals.

Yes, over-the-counter lactase supplements are generally safe for managing lactose intolerance symptoms. They provide the body with the enzyme it lacks, aiding in the digestion of dairy products.

No, not all dairy products contain high levels of lactose. Hard, aged cheeses and yogurt with active cultures have significantly less lactose and are often tolerated by individuals with lactose intolerance.

No, lactose intolerance is different from a milk allergy. Intolerance is a digestive issue caused by a lack of the lactase enzyme, while an allergy is an immune system response to milk proteins.

Lactose malabsorption is the physiological inability to digest lactose in the small intestine, while lactose intolerance is the experience of symptoms (gas, bloating, etc.) as a result. All lactose intolerant people have malabsorption, but not everyone with malabsorption has symptoms.

Doctors can test for lactase deficiency using a hydrogen breath test, which measures hydrogen levels after consuming a lactose solution. High levels indicate undigested lactose fermented by bacteria in the colon.