What Is Lactose Intolerance? Everything You Need to Know

Many people don’t produce enough of the enzyme lactase needed to digest lactose, a type of sugar found in dairy products such as milk, yogurt, and certain cheeses.

This common disorder, known as lactose intolerance, can cause significant digestive symptoms, including gas, bloating, gut discomfort, and persistent diarrhea if not managed properly.

Discover the causes of lactose intolerance and learn how to improve symptoms by making dietary adjustments and opting for lactose-free alternatives.

What is lactose intolerance? 

Lactose intolerance is a digestive condition characterized by the inability or reduced capacity to break down and digest lactose, a natural sugar found in milk products, including yogurt, cream, ice cream, and soft or unripened cheeses.  

When lactose isn’t fully broken down, it passes into the colon undigested, where it’s fermented by gut microbes. This fermentation creates gas and by-products, which can trigger a range of gastrointestinal symptoms.

While lactose malabsorption isn’t inherently harmful, it can contribute to intestinal irritation and inflammation, thereby increasing the risk of poor gut health, impaired nutrient absorption, and chronic immune responses. 

According to research published in StatPearls, it’s estimated that around 65 percent of the world's population has some degree of lactose intolerance, with prevalence varying widely across different regions. 

While up to 90 percent of East Asian adults are believed to be lactose intolerant, only around 15 percent of Northern Europeans appear to be affected, highlighting the strong genetic component of lactose intolerance.

Although there isn’t a cure for lactose intolerance, making dietary adjustments by avoiding dairy foods can alleviate symptoms and help maintain a healthy digestive system.

Watch the video below to learn more about lactose intolerance.

Lactose intolerance symptoms

Symptoms of lactose intolerance are primarily triggered by the bacterial fermentation of undigested lactose in the gastrointestinal tract.

These are common symptoms associated with lactose intolerance:

• Bloating

• Gas

• Diarrhea

• Abdominal cramps or pain

• Nausea

Symptoms typically develop within 30 minutes to 2 hours of consuming milk and dairy products and can vary in severity based on the exact underlying cause of lactose intolerance. 

While some lactose intolerant people may experience only mild digestive discomfort in response to lactose intake, others may suffer more severe symptoms, including diarrhea or even vomiting, in extreme cases.

What causes lactose intolerance?

All cases of lactose intolerance are caused by lack of or insufficient production of the lactase enzyme, which is needed to break down lactose into simple sugars that can readily be digested and absorbed.

However, there are different causes of lactase deficiency, and lactose intolerance can be grouped into several types based on their underlying cause. 

Primary lactose intolerance is the most common form, characterized by a natural decline in lactase production that begins after childhood and is primarily influenced by genetic factors.

Research published in Scientific Reports suggests that this genetic trait, commonly known as lactase non-persistence, is believed to have evolved as humans transitioned away from milk consumption after weaning. This reflects an evolutionary adaptation in populations where milk products weren’t staple food in adulthood.

Secondary lactose intolerance is often associated with gastrointestinal infections, celiac disease, irritable bowel disease (IBD), or Crohn’s disease. These conditions can trigger inflammation in the gut, which impairs the small intestine's ability to produce lactase, leading to difficulty digesting lactose.

In contrast, developmental lactose deficiency primarily affects premature infants whose underdeveloped digestive systems are unable to produce sufficient lactase.

While developmental lactose intolerance can resolve as the digestive system matures, congenital lactase deficiency, also known as congenital lactose intolerance, is a rare and untreatable condition caused by a genetic mutation that results in little to no lactase production from birth. 

How to manage lactose intolerance

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recommends that lactose-intolerant people avoid lactose-containing foods to alleviate digestive discomfort. 

In addition to making dietary adjustments, there are other steps you can take to minimize symptoms of lactose intolerance and enhance the body’s natural ability to process small amounts of milk sugar.

Here are three ways to manage lactose intolerance.

1. Keep a food diary 

For some individuals with lactose intolerance, small amounts of dairy are tolerable, while others must avoid it altogether. 

Maintaining a food diary can help you identify your personal tolerance level by tracking the foods you eat and any symptoms you experience, which enables you to adjust your diet accordingly.

2. Promote a diverse gut microbiome 

Maintaining a balanced and diverse gut microbiome plays a crucial role in digestive health. 

Specific strains of probiotic bacteria, such as Bifidobacterium, naturally produce lactase, which can help digest small amounts of lactose without experiencing digestive discomfort.

Consuming probiotic foods rich in Bifidobacterium, such as kefir, sauerkraut, kimchi, and miso, can support the growth of these helpful microbes and boosts the digestive tract's natural ability to process dairy foods in moderation. 

Research published in Nutrients investigated the role of probiotics in the management of lactose intolerance. The authors concluded, “Bifidobacterium could be an effective approach to managing lactose intolerance symptoms. Bifidobacterium supplementation for a week or less decreased abdominal distress symptoms in lactose intolerant participants.”

3. Support gut healing 

Individuals with secondary lactose intolerance caused by gut irritation and inflammation may benefit from strategies that promote gut healing. 

Avoiding ultra-processed foods and focusing on a diet rich in anti-inflammatory and gut-soothing foods, such as bone broth, fermented foods, and oily fish, can reduce inflammation and help heal the gut lining.

In addition, zinc, omega-3 fatty acids, and L-glutamine are essential nutrients needed for the regeneration of the intestinal lining, which plays a crucial role in lactase production and the digestion of milk sugars.

However, it’s important to discuss supplement use and dietary changes with a healthcare provider to ensure they align with your specific health needs. 

High and low lactose foods 

Foods with significant amounts of lactose are more likely to trigger severe symptoms in people with lactose intolerance.

High-lactose foods include:

• Milk 

• Cream

• Soft and unripened cheeses

• Ice cream

• Yogurt 

• Buttermilk

• Processed foods containing milk solids or whey

Fortunately, a wide range of lactose-free products are now available, offering suitable options for those with lactose intolerance. 

Some excellent lactose-free alternatives include:

• Hard and aged cheeses such as Parmesan, Swiss, and Gouda 

• Kefir

• Lactose-free milk products 

• Lactose-free yogurt 

• Almond milk and yogurt

• Coconut dairy alternatives 

Milk allergy vs. lactose intolerance: what’s the difference?

Symptoms of lactose intolerance are triggered by undigested lactose in the intestines. 

In contrast, a milk allergy is an immune response to milk proteins, causing systemic reactions such as hives, wheezing, and severe gastrointestinal symptoms, including vomiting and diarrhea.

Unlike lactose intolerance symptoms, milk allergies can be life-threatening and may require strict avoidance of all dairy. 

“There are various proteins in milk and dairy products that can provoke allergic reactions, including casein and whey,” explains Dr. Berg. “A2 milk lacks the A1 beta-casein protein, a common milk-derived allergen, which can help reduce digestive symptoms in some individuals with milk allergies.”

However, those with milk allergies must discuss the use of A2 milk with a healthcare provider to minimize the risk of serious allergic reactions and anaphylactic shock. 

Testing and diagnosis

Information related to lactose intolerance should be discussed with a medical professional to determine suitability based on individual health needs.

There are several tests that a healthcare provider can utilize to diagnose lactose intolerance if symptoms are indicative of lactose malabsorption. 

A lactose tolerance test assesses how well your body digests lactose by measuring blood sugar levels after consuming a lactose-rich solution. If blood sugar levels show only a minimal increase, it indicates that lactose isn’t being broken down and absorbed.

A hydrogen breath test detects hydrogen gas produced when undigested lactose is fermented in the colon, which is a strong indicator of lactose malabsorption. 

For infants and young children, a stool acidity test can be used to measure lactic acid, which is a by-product of bacterial lactose fermentation. 

These tests, combined with evaluating symptoms and dietary habits, can help determine whether digestive symptoms are caused by lactose intolerance or another underlying cause.

Key takeaways

Lactose intolerance is a widespread condition caused by an inability to digest and absorb lactose, a type of carbohydrate found in various dairy products, including milk, yogurt, and soft cheese.

To minimize digestive comfort, it’s crucial that those with lactose intolerance avoid or minimize dairy intake and instead opt for lactose-free products such as kefir, lactose-free milk, aged cheeses, and almond or coconut-based dairy alternatives. 

FAQ

1. What is lactose intolerance?

Lactose intolerance is a widespread digestive issue caused by a lack of or insufficient production of lactase, the enzyme needed to break down milk sugars known as lactose.

When undigested lactose ferments in the intestines, it can cause symptoms such as abdominal distention, gas, bloating, and diarrhea, which are common signs of lactose intolerance triggered by consuming dairy products. 

2. How can I tell if I'm lactose intolerant?

Experiencing digestive issues such as bloating, gas, abdominal pain, or diarrhea within 30 minutes to 2 hours of consuming milk and dairy products can indicate lactose intolerance.

However, it’s crucial to consult a healthcare provider for a thorough evaluation of your symptoms and proper diagnosis. 

3. Can lactose intolerance go away?

Most cases of lactose intolerance are permanent. However, individuals with secondary lactose intolerance, often caused by intestinal infections, gut irritation, or inflammation, may regain some ability to tolerate dairy products as their gut lining heals.

4. Can someone suddenly become lactose intolerant?

Yes, lactose intolerance can develop suddenly, often due to aging, gastrointestinal infections, or conditions such as celiac disease or Crohn's disease that damage the intestinal lining and reduce lactase production.

5. What can mimic lactose intolerance?

Conditions such as irritable bowel syndrome (IBS), Crohn's disease, celiac disease, and cow’s milk allergy can mimic lactose intolerance, as they can cause symptoms such as bloating, diarrhea, and digestive discomfort.

6. What is the best remedy for lactose intolerance?

The best remedy for lactose intolerance is avoiding lactose-containing dairy products such as milk, cheese, ice cream, and other dairy products. 

Certain beneficial gut microbes, such as Bifidobacterium, can break down lactose, and probiotic supplementation has been found to help some individuals tolerate small amounts of dairy without symptoms.

7. Is lactose intolerance the same as a milk allergy?

No, lactose intolerance and milk allergy are two distinct conditions. A lactose intolerance is characterized by the inability to break down and absorb lactose, whereas a milk allergy is an immune reaction to milk proteins.

While both lactose intolerance and milk allergy can cause gastrointestinal symptoms, allergic reactions to milk proteins can also trigger severe and potentially life-threatening symptoms such as hives, swelling, difficulty breathing, and anaphylaxis.

Sources

1. https://www.ncbi.nlm.nih.gov/books/NBK532285/ 

2. https://www.nature.com/articles/s41598-018-23957-4 

3. https://www.niddk.nih.gov/health-information/digestive-diseases

4. https://pmc.ncbi.nlm.nih.gov/articles/PMC10459152/