Overview
Coeliac disease (CD) and lactose intolerance (LI) are two different yet connected conditions that affect the digestive system, and disrupt the daily lives of many people. Although the two conditions have different underlying causes, they share similarities in how they impact digestive health and dietary management.
This article will explain CD and LI, including their causes, symptoms, diagnosis, and treatment options. Read on to find out about the relationship between both conditions and what you can do to manage them simultaneously.
What is coeliac disease (CD)?
CD is an autoimmune illness triggered by gluten consumption. Gluten is a protein found in rye, barley, and wheat. When those with CD consume gluten, an immune response is triggered, attacking and damaging villi (tiny hair-like cells on the lining of the small intestine) which promotes nutrient absorption. Over time, damage and inflammation to the villi means nutrients cannot be absorbed properly into the body, this is known as malabsorption.
What is lactose intolerance (LI)?
LI is a digestive disorder characterised by the body’s inability to break down or digest lactose, a recurring sugar found in dairy products. LI occurs due to a deficiency of lactase, a digestive enzyme produced by the small intestine. The role of lactase is to break down lactose in food so that the body can absorb it. A lack of lactase production in the body means that lactose remains undigested in the digestive tract, leading to uncomfortable symptoms after lactose consumption.
It is important to note that LI is different to having a milk allergy, which is caused by casein and whey proteins found in milk.
Understanding coeliac disease
Causes and risk factors
The exact causes of CD are unknown. However, it is believed to result from a combination of genetic and environmental factors.
CD can occur in genetically predisposed individuals.1 The chances of developing CD increase to 10% if a first-degree family member also has it, such as your parents or siblings.
Studies have identified that mutations to HLA-DQ genes, which are used to detect which cells belong in your body increase your risk of developing the condition.2 However, these mutations are increasingly common, suggesting that environmental factors may trigger changes in the small intestine, including:
- Having an infection in your digestive system during early childhood
- Introducing gluten-containing foods too early in the infant diet – it is typically recommended to wait until your child is 6 months old
- Not being breastfed when gluten is introduced into the diet
Other autoimmune conditions that can increase your risk of developing CD may include:2
Understanding lactose intolerance
Causes and types
LI is the inability to digest lactose due to decreased lactase production and can occur in children and adults. LI is categorised into the following three types.3
Primary LI
This is the most common type, often referred to as adult-type lactase deficiency. It occurs when lactase production in the small intestine declines with increasing age due to changes in the lactase gene.
Secondary LI
This type of deficiency arises when your small intestine produces less lactase due to damage, such as illness, injury or surgery. Diseases associated with secondary deficiency include infections, CD, and Crohn’s disease.
Congenital LI
This is an extremely rare form of lactose deficiency caused by an absence of lactase production from birth.
Both primary and congenital LI are autosomal recessive. This means both mother and father must pass on the same gene variant for the child to develop LI.
What is the relationship between coeliac disease and lactose intolerance?
Coexistence of coeliac disease and lactose intolerance
LI occurs frequently in CD patients, with an estimated 10-50% in adult patients.4 It is common for those with CD to have LI, particularly upon diagnosis. This is because, at the time of diagnosis, the lining of the small intestine is still damaged due to gluten consumption, resulting in the body’s inability to produce lactase. As LI in coeliac patients arises from damage to the small intestine, it is classified as secondary LI.5
When lactose is not broken down by lactase in the small intestine, it gets fermented by bacteria in the large intestine instead. This leads to uncomfortable symptoms, often similar to that of CD, such as:1,3
- Stomach pain and cramps
- Diarrhoea, due to malabsorption by the small intestine
- Bloating
- Gas
- Nausea
- Malnutrition, from the inability to digest food
A common symptom associated with CD but not LI is dermatitis herpetiformis, which is a rash linked to eating gluten, present in 25% of patients.1
With LI, symptoms usually develop between 30 minutes and 2 hours. Although those with CD may experience uncomfortable symptoms shortly after eating gluten, they typically develop over 48-72 hours.
However, LI in CD patients may be temporary. Once gluten is removed from the diet, the lining of the intestine can heal, and normal lactose absorption can be restored.6
As a result of an overlap in symptoms, CD is often underdiagnosed, whilst LI is overdiagnosed.5
Challenges in diagnosis
Due to an overlap in symptoms between both conditions, it is important that they are correctly diagnosed. Doctors may conduct specific tests to be able to accurately diagnose both conditions.
Diagnosing CD
Diagnosing CD can often involve the following tests:
- Clinical and physical exam to learn about your symptoms
- Blood test to test for specific antibodies produced by the immune system in response to gluten
- Biopsy where a sample of the small intestine will be collected to check for inflammation and abnormal villi
You will need to eat gluten during these tests to ensure accurate results. Only after CD is diagnosed should you start a gluten-free diet (GFD).
Diagnosis of LI
Testing for LI may involve:3
Hydrogen breath test
In this test, you will drink a liquid containing lactose and the quantity of hydrogen gas in your breath when you exhale is measured. High levels of hydrogen in your breath signify LI.
Lactose tolerance test
This test will detect how your digestive system absorbs lactose. It involves not eating or drinking 8 hours prior to the test as during the test you will drink a lactose-containing liquid. Blood samples are taken before, during, and after to measure your blood glucose levels. If blood glucose levels do not rise, it can indicate intolerance.
Stool acidity test
This test is usually for young children to measure acidity in the stool. If your stool contains lactic acid, glucose, and other byproducts, it can indicate that the body is not absorbing lactose, thus intolerance.
How can I manage coeliac disease and lactose intolerance together effectively?
Managing CD and LI together requires changing to a restricted diet and lifestyle, which can be carefully planned and discussed with a dietician.
Gluten-free and lactose-free diet
CD management mainly involves adopting a gluten-free diet (GFD), as this prevents damage to the lining of the small intestine. If you have CD, it is recommended that you adopt a GFD for life, as your symptoms can return on eating gluten and cause long-term damage.
A GFD can be discussed with you by a dietician, who may suggest avoiding foods containing barley, rye, wheat, or oat-containing foods and instead opt for gluten-free (GF) alternatives. GF products are defined as having less than 20 ppm (parts per million) of gluten, including possible contamination.7
Management of LI involves dietary modifications, typically adopting a dairy-free diet and consuming lactose-free options instead. This means avoiding milk, butter, cheese, and cream products. However, some people find that there are certain lactose products they can tolerate in certain amounts over others. Data suggests that adults may be able to ingest 12 g of lactose in a single dose.3
Following these diets, it is vital to focus on eating nutrient-dense foods, including:7
- Fruits
- Vegetables
- Lean proteins
- Gluten-free whole grains, such as millet, rice, and quinoa
Nutritional considerations and potential deficiencies
Nutritional deficiencies are common in those with CD due to the lack of absorption of micronutrients and macronutrients in the small intestine. Approximately 70% of CD patients have reduced bone mineral density, including osteopenia and osteoporosis due to impaired vitamin D and calcium absorption.4 Alongside a calcium-rich GFD, you may require supplements to target other common nutritional deficiencies, such as:
Dairy products also have positive effects on bone health, particularly in bone growth for children. Dairy is a source of calcium, vitamin D, protein, and minerals including magnesium, potassium, phosphorus, and zinc, therefore, the complete avoidance of all dairy products is not recommended.4
Those with LI should instead restrict lactose, rather than avoid it, so that they do not lose the nutritional value of dairy in their diet. Over-the-counter (OTC) lactase supplements may be an option to help you digest lactose-containing products, but this should be discussed with your doctor before trying.
Lifestyle adjustments
Both CD and LI may be managed by adopting some lifestyle adjustments, such as:7
- Checking for cross-contamination when going to restaurants, or when sharing kitchen utensils and appliances
- Checking processed foods for gluten and lactose
- Tracking foods eaten and their symptoms for future avoidance
- Scheduling regular health check-ups to ensure both conditions are being managed effectively to avoid complications
Summary
- Coeliac disease is an autoimmune illness characterised by damage to the lining of the small intestine from gluten consumption, resulting in nutrient malabsorption
- Lactose intolerance is a digestive disorder caused by the body’s inability to break down lactose due to a lack of the digestive enzyme, lactase
- Both conditions can coexist as damage to the small intestine lining from gluten can cause secondary lactase deficiency
- They both display similar symptoms, including stomach pain, diarrhoea, nausea, and bloating, causing difficulty in diagnosis
- Managing both conditions involves adopting a gluten-free and lactose-free diet, ensuring that nutritional deficiencies are targeted and lifestyle adjustments made to maintain overall health
References
- Wu X, Qian L, Liu K, Wu J, Shan Z. Gastrointestinal microbiome and gluten in celiac disease. Ann Med [Internet]. [cited 2024 May 13]; 53(1):1797–805. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8519548/.
- Martina S, Fabiola F, Federica G, Chiara B, Gioacchino L, Francesco DM, et al. Genetic susceptibilty and celiac disease: what role do HLA haplotypes play? Acta Biomed [Internet]. 2018 [cited 2024 May 13]; 89(Suppl 9):17–21. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6502200/.
- Di Costanzo M, Berni Canani R. Lactose Intolerance: Common Misunderstandings. Ann Nutr Metab [Internet]. 2018 [cited 2024 May 14]; 73 Suppl 4:30–7. Available from: https://pubmed.ncbi.nlm.nih.gov/30783042/.
- Alkalay MJ. Nutrition in Patients with Lactose Malabsorption, Celiac Disease, and Related Disorders. Nutrients [Internet]. 2021 [cited 2024 May 15]; 14(1):2. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8746545/.
- Aaron L, Patricia W, Ajay R, Torsten M. Celiac Disease and Lactose Intolerance. International Journal of Celiac Disease [Internet]. 2019 [cited 2024 May 15]; 6(3):68–70. Available from: https://pubs.sciepub.com/ijcd/6/3/8/index.html.
- Usai-Satta P, Lai M, Oppia F. Lactose Malabsorption and Presumed Related Disorders: A Review of Current Evidence. Nutrients [Internet]. 2022 [cited 2024 May 15]; 14(3):584. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8838180/.
- Aljada B, Zohni A, El-Matary W. The Gluten-Free Diet for Celiac Disease and Beyond. Nutrients [Internet]. 2021 [cited 2024 May 15]; 13(11):3993. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8625243/.