Lactose Intolerance

Many people newly diagnosed with coeliac disease notice that dairy causes problems — bloating, cramping, loose stools — even after they’ve gone gluten-free. This isn’t a coincidence, and it doesn’t necessarily mean they have a permanent dairy problem. Secondary lactose intolerance is a common and usually temporary consequence of coeliac-related gut damage.

Why Coeliacs Often Develop Lactose Intolerance

Lactose is the sugar in milk and dairy products. To digest it, your gut needs an enzyme called lactase. Lactase is produced by the cells that line the tips of the intestinal villi — the same villi that coeliac disease destroys.

When villous atrophy is active, lactase production drops. Without enough lactase, lactose passes into the large intestine undigested, where gut bacteria ferment it — producing gas, cramping, and diarrhoea. The symptoms can be significant and are easily confused with ongoing gluten exposure, which makes troubleshooting post-diagnosis harder.

This is called secondary lactose intolerance — secondary because it’s caused by another condition (coeliac disease) rather than being a primary genetic inability to digest lactose. The distinction matters because secondary lactose intolerance is typically reversible.

As the gut heals on a gluten-free diet, villi regenerate and lactase production recovers. For most people, dairy tolerance returns within 6–24 months of strict gluten-free eating. Some people find they tolerate hard aged cheeses (which are naturally very low in lactose) before they tolerate milk or soft cheese, because the lactose content varies considerably across dairy types.

A small number of coeliacs also have primary (genetic) lactose intolerance, which existed before the coeliac diagnosis and won’t resolve with gut healing. And separately, some coeliacs do have a true dairy allergy or a reaction to the casein protein in milk — this is different from lactose intolerance and won’t improve over time.

If you’re eliminating dairy as well as gluten post-diagnosis, it’s worth reassessing dairy tolerance after 12–18 months of a strict gluten-free diet, ideally with guidance from a dietitian.

What This Means for You

If dairy is causing symptoms right now, cutting it out temporarily makes sense while your gut heals. But don’t assume it’s a permanent restriction. Give the GF diet time to work, then reintroduce dairy gradually. Most people find it comes back without issue.

Related in the Coeliac Alphabet: Enteropathy · Intestinal Villi · Villous Atrophy · back to the full A–Z.