What is Deficient in Lactose Intolerance? The Lactase Enzyme Explored

Did you know that an estimated 65% of the world's population experiences lactose malabsorption after infancy? This widespread condition, known as lactose intolerance, is fundamentally defined by a deficiency in one crucial digestive enzyme: lactase.

Quick Summary

Lactose intolerance is caused by a lactase enzyme deficiency in the small intestine, which impairs the digestion of milk sugar, leading to various gastrointestinal symptoms.

Key Points

• Lactase Deficiency: Lactose intolerance is caused by a deficiency of the lactase enzyme, which breaks down milk sugar (lactose) in the small intestine.

• Diverse Causes: The deficiency can be primary (genetic, age-related), secondary (due to illness/injury), congenital (from birth), or developmental (in premature babies).

• Gastrointestinal Symptoms: When undigested lactose reaches the colon, bacteria ferment it, producing gas that leads to bloating, cramps, and diarrhea.

• Not an Allergy: Lactose intolerance is a digestive issue, unlike a milk allergy, which is an immune system response to milk proteins and can cause more severe reactions.

• Effective Management: Symptoms can be controlled with dietary modifications, the use of lactase enzyme supplements, and in some cases, probiotics.

• Calcium and Vitamin D: Managing the condition requires attention to nutrient intake, especially calcium and vitamin D, which are commonly sourced from dairy.

• Professional Diagnosis: Accurate diagnosis by a healthcare professional is important to rule out other conditions with similar symptoms, like celiac disease or IBS.

What is the Lactase Enzyme?

Before delving into the deficiency, it's essential to understand the role of the lactase enzyme. Produced by the lining of the small intestine, lactase is a specialized enzyme crucial for breaking down lactose, the primary sugar found in milk and dairy products. Lactase acts as a molecular scissor, splitting the disaccharide lactose into two simpler, absorbable sugars: glucose and galactose. These simpler sugars are then easily absorbed into the bloodstream, providing energy.

What is Deficient in Lactose Intolerance?

The short and direct answer is the lactase enzyme. Lactose intolerance is not an allergy; it is a digestive condition resulting from the small intestine's insufficient production of lactase. When lactase levels are low, undigested lactose passes through the small intestine and into the colon, where it causes a cascade of uncomfortable symptoms. The severity of symptoms can vary based on an individual's level of lactase production and the amount of lactose consumed.

Types of Lactase Deficiency

Lactase deficiency is not a single condition but can manifest in four distinct forms, each with a different cause.

Primary (Lactase Non-persistence)

This is the most common type and is genetically determined. After infancy, lactase production gradually decreases, a process known as lactase non-persistence. This decline is a normal part of development in most human populations globally, although the rate and timing vary significantly by ethnicity. In many people of African, Asian, or Hispanic descent, lactase activity drops sharply after weaning, while some of European descent may retain higher levels of lactase into adulthood.

Secondary (Acquired)

Secondary lactase deficiency occurs when the small intestine's lining is damaged by an illness, injury, or surgery. Common causes include gastrointestinal infections, celiac disease, or Crohn's disease. Unlike the primary type, this deficiency is often temporary. Once the underlying condition is treated and the intestinal lining heals, lactase levels can recover.

Congenital (From Birth)

An extremely rare inherited disorder, congenital lactase deficiency means infants are born with little to no lactase production. If untreated, this condition can be life-threatening and causes severe watery diarrhea from birth. It is inherited in an autosomal recessive pattern, meaning both parents must carry the gene mutation. These infants require a specialized lactose-free formula for survival.

Developmental (In Premature Infants)

Premature infants, especially those born before 34 weeks of gestation, can have a temporary lactase deficiency because the small intestine does not fully develop lactase-producing cells until the third trimester. This is a temporary condition that typically resolves as the infant matures.

The Process: From Undigested Lactose to Symptoms

When a person with lactase deficiency consumes lactose, the undigested milk sugar travels to the large intestine. Here, the large intestinal bacteria ferment the lactose, producing gasses such as hydrogen, carbon dioxide, and methane. This fermentation is the cause of several classic lactose intolerance symptoms.

• Bloating and Gas: The gasses produced by fermentation build up, leading to a swollen feeling in the abdomen and increased flatulence.
• Diarrhea: The presence of undigested lactose in the colon creates an osmotic effect, drawing water into the large intestine and causing watery stools.
• Abdominal Cramps and Pain: The gas and fluid buildup can cause uncomfortable abdominal pain and cramping.

Diagnosing Lactase Deficiency

Healthcare providers use several methods to diagnose lactase deficiency. A diagnosis is crucial to rule out other conditions with similar symptoms, such as irritable bowel syndrome (IBS) or celiac disease.

• Hydrogen Breath Test: After an overnight fast, the patient drinks a liquid containing lactose. Breath samples are then collected at intervals. High levels of hydrogen in the breath indicate that the colon's bacteria are fermenting undigested lactose.
• Lactose Tolerance Test: This test measures blood glucose levels before and after consuming a lactose solution. If glucose levels do not rise significantly, it suggests the body is not digesting and absorbing lactose.
• Stool Acidity Test: Used for infants and young children, this test checks stool samples for excess lactic acid and other fatty acids, which are byproducts of bacterial fermentation of lactose.
• Elimination Diet: Some doctors may simply recommend a temporary two-week diet free of dairy to see if symptoms improve, followed by reintroduction to confirm sensitivity.

Managing Your Lactase Deficiency

There is no cure for genetically based lactase deficiency, but symptoms can be effectively managed through several strategies.

Dietary Adjustments

Limiting or avoiding lactose-containing foods is the most common management strategy. Many people can tolerate small amounts of lactose, and incorporating dairy into meals can slow digestion and lessen symptoms. Many supermarkets now offer a wide variety of lactose-free and lactose-reduced dairy products, including milk, cheese, and ice cream.

Lactase Supplements

Over-the-counter lactase enzyme supplements (pills or drops) can be taken just before consuming dairy products to help the body break down lactose. These are a convenient option for enjoying dairy without discomfort.

Probiotics

Probiotic supplements and fermented foods like yogurt with live and active cultures can help improve lactose digestion in some individuals. Certain bacteria, like Lactobacillus and Bifidobacterium, can produce their own lactase, aiding the process.

Nutrient Supplementation

Since dairy is a primary source of calcium and vitamin D, those significantly reducing their intake should seek alternative sources to prevent nutritional deficiencies.

• Calcium Sources: Fortified plant-based milks (soy, almond, oat), fortified juices, cereals, leafy green vegetables (kale, broccoli), and canned fish with bones (salmon, sardines).
• Vitamin D Sources: In addition to fortified foods, getting sunlight and eating foods like eggs and fatty fish can help maintain adequate vitamin D levels.

Table: Lactose Intolerance vs. Milk Allergy

Feature	Lactose Intolerance	Milk Allergy
Cause	Deficiency of the enzyme lactase.	Immune system reaction to milk proteins (casein or whey).
Body System Involved	Digestive system.	Immune system.
Onset of Symptoms	Generally 30 minutes to two hours after consumption.	Can be rapid, from minutes to hours after exposure.
Type of Reaction	Food intolerance, a digestive issue.	True food allergy.
Potential Severity	Symptoms are uncomfortable but not life-threatening.	Can cause severe reactions, including life-threatening anaphylaxis.
Amount Consumed	Individuals can often tolerate small amounts of lactose, depending on severity.	Even tiny amounts of milk protein can trigger a reaction.

Conclusion: Living with Lactose Intolerance

Ultimately, what is deficient in lactose intolerance is the lactase enzyme, leading to the maldigestion of lactose. However, a diagnosis of lactose intolerance is not a sentence of dietary restriction and discomfort. With modern understanding, management is highly effective, allowing most individuals to enjoy a balanced diet with proper adjustments. By understanding the specific type of deficiency, using lactase supplements, and exploring the many lactose-free alternatives available, those affected can successfully manage their symptoms. Consulting a healthcare provider for an accurate diagnosis and a registered dietitian for dietary guidance is the best approach to developing a personalized and effective management plan. The key is knowledge and empowerment, turning a once-challenging condition into a manageable part of life.

For more information on digestive health, consult the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) website.

References

• Mayo Clinic: Lactose intolerance - Symptoms & causes - https://www.mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232
• National Institutes of Health (NIH) | (.gov): Definition & Facts for Lactose Intolerance - https://www.niddk.nih.gov/health-information/digestive-diseases/lactose-intolerance/definition-facts
• NCBI Bookshelf: Lactose Intolerance - StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK532285/
• Medscape eMedicine: Lactose Intolerance: Background, Etiology, Pathophysiology - https://emedicine.medscape.com/article/187249-overview
• Cleveland Clinic: Lactose Intolerance: Symptoms, Diagnostic Tests & Treatment - https://my.clevelandclinic.org/health/diseases/7317-lactose-intolerance

Frequently Asked Questions

What is the primary cause of lactose intolerance?

The primary cause is a deficiency of the lactase enzyme in the small intestine. This is most often a natural, genetically determined decline in lactase production after infancy.

Can lactase deficiency be temporary?

Yes, secondary lactase deficiency can be temporary. It is often caused by an intestinal illness, infection, or injury, and may resolve once the underlying issue is treated and the small intestine heals.

What happens to undigested lactose in the body?

Undigested lactose travels to the large intestine, where it is fermented by bacteria. This process creates gasses and fatty acids that cause bloating, gas, and pain.

How do doctors diagnose lactase deficiency?

Diagnosis typically involves a hydrogen breath test, which measures hydrogen levels in the breath after consuming lactose. Other methods include a lactose tolerance blood test and, for infants, a stool acidity test.

What are good sources of calcium for someone with lactose intolerance?

Excellent non-dairy sources of calcium include fortified plant-based milks, fortified cereals and juices, leafy green vegetables like kale and broccoli, and canned fish with edible bones.

How do lactase enzyme supplements work?

Taken before eating dairy products, lactase supplements provide the necessary enzyme to break down lactose in the gut, thereby preventing symptoms. They are available in pill or drop form.

Can probiotics help manage lactose intolerance?

Some research suggests that certain probiotic bacteria, like those with lactase-producing properties found in yogurt with live cultures, may aid in lactose digestion and improve tolerance.

Is congenital lactase deficiency a lifelong condition?

Yes, congenital lactase deficiency is a rare, inherited condition that is permanent. Infants with this deficiency must be fed a lactose-free diet for life.