Understanding Why Should Celiacs Avoid Dairy: Reasons Beyond Lactose

October 6, 2025 •

5 min read

According to Beyond Celiac, as many as 50% of newly diagnosed celiac disease patients with malabsorption experience lactose intolerance. This makes it a common challenge to understand why should celiacs avoid dairy, especially during the initial gut healing phases of a gluten-free diet. While not all dairy needs to be eliminated permanently, the reasons for temporary removal are crucial for managing symptoms and promoting recovery.

Quick Summary

Newly diagnosed celiacs often temporarily remove dairy due to intestinal damage impairing lactase production, causing lactose intolerance. Some may also have sensitivities to milk proteins like casein or experience cross-reactivity.

Key Points

Secondary lactose intolerance is frequent in newly diagnosed celiacs because intestinal damage reduces lactase production.
Gut healing can resolve this intolerance, allowing many celiacs to reintroduce dairy after a few months on a strict gluten-free diet.
Casein sensitivity is another potential issue, where some celiacs react to milk proteins rather than lactose, possibly requiring long-term dairy avoidance.
Cross-reactivity is a theory suggesting the immune system may mistake dairy proteins for gluten, leading to continued symptoms in some individuals.
Alternative calcium and vitamin D sources are essential when avoiding dairy to prevent nutritional deficiencies and support bone health.
Gradual dairy reintroduction should be done carefully and methodically after the gut has healed, starting with low-lactose items.
Distinguishing lactose intolerance from a dairy protein issue is critical for personalized dietary management and effective symptom control.

Secondary Lactose Intolerance and Gut Healing

For many people with celiac disease, the need to avoid dairy is directly linked to the state of their small intestine. When a person with celiac disease ingests gluten, their immune system mounts a response that damages the villi lining the small intestine. These tiny, finger-like projections are responsible for nutrient absorption and, crucially, for producing the lactase enzyme that digests lactose, the sugar found in milk.

When the villi are damaged, the body can't produce enough lactase to break down lactose effectively. This leads to what is known as secondary lactose intolerance. Symptoms often mimic celiac disease itself, including bloating, gas, abdominal pain, and diarrhea. However, once a person with celiac disease adheres strictly to a gluten-free diet, the small intestine can begin to heal. As the villi recover, lactase production often returns to normal, and the ability to tolerate dairy may improve over time. For most, this temporary dairy avoidance is a bridge to better gut health, not a permanent restriction.

The Difference Between Dairy Intolerance and Allergy

It is important to distinguish between lactose intolerance and other adverse reactions to dairy. Lactose intolerance is not an immune-mediated response but a digestive issue caused by a lack of the lactase enzyme. A milk allergy, by contrast, is a true immune response to milk proteins (casein and whey) and can cause more severe symptoms. For some celiacs, especially those with persistent symptoms despite a strict gluten-free diet, a co-existing milk protein sensitivity could be the culprit. This requires a longer, sometimes permanent, avoidance of all dairy products, not just lactose.

Potential Complications from Milk Proteins

Beyond lactose, there is another, more complex reason why some celiacs may react to dairy: milk proteins. Cow's milk contains two main proteins, casein and whey. Some individuals may be sensitive to one or both of these proteins, and the presence of casein, in particular, may continue to trigger an inflammatory response even after gluten has been completely removed from the diet. This is not an autoimmune attack on the intestines like with gluten, but a sensitivity that can prolong symptoms and slow the gut healing process. Anecdotal evidence from celiac forums suggests that for some, cutting both gluten and dairy is necessary to achieve full symptom remission. While the science on the precise mechanisms is still developing, the observed improvements for some individuals suggest it is a valid consideration.

Cross-Reactivity and the Immune System

Some theories suggest a phenomenon called molecular mimicry or cross-reactivity, where the immune system, sensitized by a lifetime of gluten exposure, may mistake similar protein structures in other foods for gluten. While this is a topic with evolving research, and some experts have dismissed anecdotal reports, other celiac sufferers claim to have reacted to non-glutenous foods due to this concept. Cow's milk proteins, especially casein, have been mentioned as a potential cross-reactor. The idea is that an already over-reactive immune system may be unable to distinguish between gluten proteins and similar-looking dairy proteins, causing a flare-up of symptoms and hindering recovery.

Safely Reintroducing Dairy after Gut Healing

For many celiacs, the goal is not permanent dairy elimination but temporary removal to aid intestinal recovery. When considering reintroducing dairy, a slow and methodical approach is best, and should be done in consultation with a healthcare professional or registered dietitian.

Here is a common strategy for reintroducing dairy:

Start small: Begin with products that are naturally low in lactose, such as hard, aged cheeses (e.g., parmesan, cheddar).
Monitor symptoms: Keep a detailed food and symptom diary to track any adverse reactions.
Gradual progression: If hard cheeses are tolerated, move on to yogurt, which contains beneficial live cultures that help break down lactose.
Introduce higher-lactose products: Only after tolerating lower-lactose options should you try higher-lactose dairy like milk and ice cream.
Consider lactose-free products: For those who find permanent lactose intolerance, lactose-free dairy options are widely available.

Important Nutritional Considerations

Dairy products are significant sources of calcium and vitamin D, both essential for bone health, especially for celiacs who are already at risk for nutritional deficiencies and osteoporosis. If you must avoid dairy long-term, it's vital to find alternative sources to prevent nutrient shortfalls.

Calcium-fortified alternatives: Opt for plant-based milks (almond, soy, rice) fortified with calcium and vitamin D.
Dairy-free sources: Include other calcium-rich foods such as canned sardines with bones, fortified tofu, leafy greens (like kale and broccoli), and nuts.
Consider supplements: Work with a doctor or dietitian to see if calcium and vitamin D supplements are necessary.

Conclusion

Understanding the nuanced relationship between celiac disease and dairy is key to effective management and gut healing. While secondary lactose intolerance is a common, often temporary issue for newly diagnosed celiacs, other factors like casein sensitivity and potential immune cross-reactivity can necessitate longer-term dairy avoidance for some. Working with a healthcare team to identify individual triggers is crucial. By managing the gut healing process strategically—with careful elimination and mindful reintroduction—many can enjoy a wider dietary scope and continue their path toward better health.


Aspect	Secondary Lactose Intolerance	Casein Sensitivity / Cross-Reactivity
Cause	Gluten-induced damage to intestinal villi, reducing lactase enzyme.	Immune system reaction to milk protein (casein).
Symptoms	Gas, bloating, diarrhea, cramps after consuming lactose.	Can include digestive issues, skin problems, or persistent celiac symptoms.
Timing	Usually temporary, resolves as gut heals on a gluten-free diet.	Can be a permanent issue for some individuals.
Resolution	Improves with time on a strict gluten-free diet; gradual reintroduction of dairy often possible.	Requires complete avoidance of dairy and milk proteins; reintroduction may not be possible or necessary.
Diagnosis	Diagnosed via a hydrogen breath test or an elimination diet trial.	Diagnosed via elimination and reintroduction, potentially in conjunction with specialist evaluation.

Key takeaways

Secondary lactose intolerance is common in newly diagnosed celiacs due to villi damage from gluten.
Intolerance is often temporary, resolving as the small intestine heals on a strict gluten-free diet.
Some celiacs may have a separate, persistent sensitivity to milk proteins like casein, requiring longer dairy avoidance.
Potential immune cross-reactivity with milk proteins could prolong symptoms for some individuals.
Nutrient intake, especially calcium and vitamin D, must be carefully monitored if dairy is eliminated long-term.
Dairy can often be reintroduced gradually after the gut has healed, starting with low-lactose products like hard cheeses.

Frequently Asked Questions

For most individuals with celiac disease, the lactose intolerance is a temporary condition that resolves as the small intestine heals on a strict gluten-free diet. As the villi recover, lactase production returns to normal, allowing for the reintroduction of dairy.

Lactose intolerance is a digestive issue caused by the body's inability to digest lactose due to insufficient lactase. A milk allergy is an immune system reaction to milk proteins, like casein and whey, and can cause more severe, sometimes life-threatening, allergic reactions.

The timeframe varies by individual, but many nutritionists recommend eliminating dairy for a period of several weeks to up to a year to allow the gut to heal fully. Dairy can then be reintroduced slowly to test tolerance.

Yes, for some celiacs, sensitivity to the milk protein casein can cause ongoing symptoms like bloating and digestive issues, even when strictly avoiding gluten. Some people find that eliminating casein resolves these persistent symptoms.

To get enough calcium and vitamin D, celiacs can consume fortified plant-based milks, calcium-rich foods like leafy greens, fortified cereals, and canned fish with bones. Supplements may also be necessary, and consultation with a dietitian is recommended.

Cross-reactivity is a theory suggesting that the immune system, sensitized by gluten, may react to proteins in other foods, like casein, that have similar molecular structures. For some individuals, this may trigger an immune response and prolong symptoms.

After a period of avoidance, it is often recommended to start with dairy products naturally low in lactose, such as hard, aged cheeses and yogurt, which contain cultures that help digest lactose. Monitoring symptoms is key during this process.