An estimated 68% of the global population experiences some degree of lactose intolerance, making it one of the most common digestive disorders worldwide. For many, the simple pleasure of consuming dairy becomes a source of anxiety and discomfort. In the long term, lactose intolerance may negatively affect health by increasing the risk of nutrient deficiencies. This is why learning to manage the condition appropriately is essential.
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What Is Lactose Intolerance?
Lactose is a sugar (called a disaccharide, composed of one glucose and one galactose molecule linked together) found naturally in cow's, goat's, and sheep's milk products unless removed.
Lactose intolerance is the presence of digestive symptoms after ingesting lactose due to lactose malabsorption. Lactose malabsorption, which affects 65% of adults worldwide, is the inability to digest lactose in the first portion of the small intestine, called the duodenum, into its constituents due to low levels of the lactase digestive enzyme. While everyone with lactose intolerance has lactose malabsorption, only those with lactose malabsorption and associated digestive symptoms have lactose intolerance. (9, 14)
Lactose Intolerance Signs & Symptoms
When lactase levels are insufficient, undigested lactose travels into the colon. Here, lactose draws water into the colon and undergoes fermentation by the resident bacteria, producing excess gases. The increase of water and gas in the colon leads to the hallmark symptoms of lactose intolerance, which include:
The timing and severity of symptoms depend on a person's sensitivity, intestinal transit time, and the amount of lactose consumed. While symptoms usually present within 30 minutes to two hours after lactose exposure, they can occur up to two days after eating lactose. (2, 14)
Root Causes of Lactose Intolerance
Lactose intolerance is caused by a deficiency in lactase, the digestive enzyme produced by small intestinal cells that breaks down lactose. Lactose intolerance is categorized into four predominant subtypes: congenital, primary, secondary, and developmental.
Congenital lactose intolerance, the rarest subtype, is an inherited genetic condition that presents in newborn babies when they first consume milk.
Primary lactose intolerance is the most common subtype in adults globally and usually presents after childhood. It is associated with aging and the deactivation of lactase genes. Lactase levels decline as these genes are deactivated, and lactose intolerance can develop. Primary lactose intolerance is also referred to as lactase nonpersistence. (2, 8)
Secondary, or acquired, lactase intolerance may develop in small intestinal illness or with certain medications. Small intestinal mucosal damage impairs lactase production, resulting in an enzymatic deficiency. Causes of secondary lactase deficiency include acute gastrointestinal infections (e.g., rotavirus and giardia), Crohn's disease, celiac disease, and small intestinal bacterial overgrowth (SIBO). Medical treatments, such as surgery, chemotherapy, and radiation, can also result in acquired lactose intolerance. Secondary lactose intolerance may not be permanent; lactose tolerance can improve as the small intestine recovers from injury. (2, 14)
Developmental lactose intolerance may occur in premature babies. This differs from congenital lactose intolerance as it is not related to genetics but is secondary to an underdeveloped small intestine. Developmental lactose intolerance usually improves/resolves as the baby ages and the small intestine matures. (14)
How to Diagnose Lactose Intolerance
Lactose intolerance can be diagnosed clinically based on the presence of lactose-related digestive symptoms that resolve with dietary lactose elimination and return with reintroduction.
However, the following steps can be taken to confirm the diagnosis, rule out other conditions that mimic lactose intolerance symptoms, and identify the causes of secondary lactose intolerance.
Step 1: Lactose Intolerance Tests
The lactose hydrogen breath test is the most commonly utilized test to diagnose lactose intolerance in the clinical setting because it is positive in 90% of patients with lactose malabsorption. This test measures hydrogen gas in breath samples collected by the patient at home after they take an oral dose of lactose. A test is considered positive if hydrogen concentrations exceed 20 ppm over baseline within three hours. Recent use of oral antibiotics, recent high colonic enema, and smoking may lead to inaccurate results. (22)
The following lactose hydrogen breath tests are available to order through Rupa Health:
- Lactose Malabsorption Breath Test by Commonwealth Diagnostics International, Inc.
- Lactose Intolerance Breath Test by Aerodiagnostics LLC
- trio-smart Malabsorption Breath Test - Lactose by Gemelli Biotech
Alternatively, the lactose tolerance test involves administering an oral dose of 1-1.5 grams of lactose per kilogram of body weight and measuring serial blood glucose levels over two hours. The test is positive if intestinal symptoms occur and blood glucose increases less than 20 mg/dL (1.1 mmol/L) above the fasting level. This test is less commonly utilized because it has a higher rate of false-positive and false-negative results than the lactose hydrogen breath test. (22)
Step 2: Tests to Investigate the Root Cause of Lactose Intolerance
Patients with secondary lactose intolerance require additional evaluation to identify the primary underlying problem.
Tests that can be considered include those to rule out SIBO, celiac disease, Crohn's disease, and acute gastrointestinal infection. The following labs can help do so:
Step 3: Tests to Customize Lactose Intolerance Treatment Plans
Exclusion of dairy products from the diet can lead to nutrient deficiencies, as dairy is a major source of calcium, phosphorus, choline, riboflavin, vitamin B12, and vitamin A in the United States (7).
The following micronutrient tests help doctors identify nutrient insufficiencies and better recommend appropriate nutritional recommendations for meeting nutritional intake goals:
- Micronutrient Test by SpectraCell
- Cellular Micronutrient Assay by Cell Science Systems
- NutrEva FMV by Genova Diagnostics
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Treatment Plan for Lactose Intolerance
Dietary adjustment is the primary therapy for all patients with lactose intolerance. Treatment protocols should be personalized based on lab findings and patient preferences. The following treatment protocol can be applied to any case of lactose intolerance, regardless of cause.
Step 1: Low-Lactose Diet
Here's Why This Is Important:
A low-lactose diet is the therapeutic dietary intervention recommended for lactose-intolerant people.
How Do You Do This?
Most people with lactose intolerance do not require a completely lactose-free diet and can tolerate up to 12-15 grams of lactose (equivalent to 8-12 oz of milk) daily. Dairy foods are good sources of protein, calcium, phosphorus, potassium, and vitamins A, D, and Bs, and they provide health benefits when incorporated into the diet. As such, part of the treatment plan should include experimenting with various dairy products and serving sizes to test the patient's lactose sensitivity and tolerance levels. (22)
Your doctor may recommend a 4-6 week strict dietary elimination of all lactose-containing foods to observe the resolution of digestive symptoms and make a clinical diagnosis of lactose intolerance. Many plant-based dairy alternatives are commercially available and can enhance elimination compliance. After this, lactose-containing foods are reintroduced every few days to customize the diet according to the patient's tolerance.
The following foods contain high amounts of lactose and are generally eliminated or restricted to small quantities:
- Milk, buttermilk, and cream
- Evaporated and condensed milk
- Cheese spreads
- Ice cream
- Sour cream
- Whey (15)
The following foods contain smaller amounts of lactose and tend to be better tolerated:
- Hard, aged cheeses (e.g., Swiss, parmesan, cheddar)
- Cottage, ricotta, and feta cheeses
- Kefir
- Reduced-lactose milk
- Yogurt with live probiotic cultures (15)
Be mindful of foods with hidden sources of lactose, including (2):
- Bread and baked goods
- Pancake, biscuit, and cookie mixes
- Breakfast cereals
- Instant potatoes, soups, and breakfast drinks
- Margarine
- Non-kosher lunch meats
- Salad dressings
- Candy
Step 2: Nutritional Supplementation
Here's Why This Is Important:
Nutritional replacement, including digestive enzymes, dietary supplements, and probiotics, ensures that individuals with lactose intolerance maintain optimal health and manage their digestive symptoms.
How Do You Do This?
Patients following a low-lactose diet are at a higher risk for calcium and vitamin D deficiencies. Calcium and vitamin D supplementations should be recommended to patients who do not meet the recommended dietary allowance for these nutrients through diet alone. The RDAs for calcium and vitamin D vary depending on sex and age:
Lactase enzyme supplements, such as LACTAID®, can be taken with lactose-containing meals to reduce clinical symptoms. Lactase enzymes support lactose digestion, so elimination from the diet does not need to be as strict, allowing the patient more freedom in dietary choices.
Oral Lactobacillus spp. probiotics, administered in doses ranging from 10 million to 10 billion CFU daily, have been shown to improve lactose hydrogen breath tests and reduce clinical symptoms of diarrhea, abdominal cramping, and vomiting associated with lactose challenges. The most common probiotics used in lactose intolerance protocols include L. acidophilus, L. reuteri, L. rhamnosus, and L. bulgaricus. (16, 19)
Step 3: Treat the Cause
In secondary lactase deficiency, treatment is directed at the underlying cause. Strategies may include:
- Antibiotics or herbal antimicrobials to eradicate SIBO or other gastrointestinal infection
- Gluten-free diet for managing celiac disease
- Anti-inflammatory and immunomodulating modalities to address Crohn's disease
You can check out the Rupa Health Magazine for articles discussing treatment strategies and protocols specific to these conditions.
The Risks of Lactose Intolerance
Eating lactose will not cause any permanent damage to the gastrointestinal tract. However, if not managed properly, one of the primary concerns of lactose intolerance is nutritional deficiency – particularly of calcium and vitamin D. These nutrients are essential for maintaining bone health, and their deficiency can lead to osteoporosis and increased fracture risk. (18)
Misdiagnosis or self-diagnosis of lactose intolerance without professional guidance can lead to overlooking conditions like celiac disease or inflammatory bowel disease, which can lead to permanent gastrointestinal damage and severe complications when not treated appropriately.
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Key Takeaways:
- Lactose intolerance is a common digestive condition characterized by gastrointestinal symptoms caused by a lactase deficiency.
- A holistic approach to treating lactose intolerance includes identifying and (if present) treating underlying causes of lactose intolerance while implementing dietary modifications to limit lactose exposure. Precautions should also be taken to manage digestive symptoms and prevent nutritional deficiencies due to dietary restrictions.
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