Intestinal villi and celiac disease: what gluten does to your gut

Intestinal villi are tiny, finger-shaped folds in your small intestine. They enlarge the surface that absorbs your food. In celiac disease, your immune system treats gluten as a threat.

That reaction can gradually flatten the villi. As a result, your gut absorbs nutrients less well.

I think 'villi' often gets explained far too abstractly. So here I walk through the mechanism step by step.

Good news up front: villi can recover in many cases. That makes this a story with perspective.

What are intestinal villi?

Intestinal villi are microscopically small projections on the inner lining of your small intestine. Each villus is full of tiny blood vessels that take up nutrients from your food. According to the Voedingscentrum, the Dutch nutrition institute, they hugely enlarge the absorbing surface so your gut takes up vitamins and minerals well.

Without villi, your small intestine would be a smooth tube. With villi, the absorbing surface is many times larger.

On each villus sit even smaller hairs, the microvilli. These make the absorbing surface finer still.

The healthier the villi, the better your body pulls nutrients from your food.

Each villus is only about a millimetre long. Yet these small structures largely decide how well you absorb food.

Some estimates compare the total surface of a healthy small intestine to a tennis court.

In celiac disease, this fine surface gets damaged. A smoother lining absorbs less efficiently.

What does gluten do to your villi in celiac disease?

In celiac disease, your immune system sees gluten as an intruder. Gluten is a protein in wheat, rye and barley. Your body then makes antibodies that also hit your own gut tissue, so the villi can gradually flatten over time, a process called villous atrophy.

Researchers discovered in 1997 that an enzyme plays a key role here, tissue transglutaminase, or tTG for short (Dieterich, 1997). Your immune system makes antibodies against this own enzyme.

These anti-tTG antibodies are exactly what a blood test looks for. Want to know how that works? Have a look at which blood values indicate celiac disease.

In short: gluten triggers an immune reaction. That reaction damages the gut tissue. In people without celiac disease, this does not happen. The difference lies in the inherited predisposition and the immune system.

The inflammation and flattening usually happen gradually. Symptoms can therefore stay mild or vague for a long time.

Gluten is not only in bread. It also turns up in pasta, biscuits, beer and many ready-made products.

Not everyone with celiac disease notices clear gut symptoms. Sometimes fatigue or deficiencies stand out instead. That is why celiac disease is sometimes called a chameleon among conditions.

The Marsh classification: grades of villous damage

Doctors often grade the damage to villi with the Marsh classification. It runs from normal mucosa (Marsh 0) to fully flattened villi (Marsh 3c). The scale simply describes how far inflammation may have progressed, summed up below in plain language.

A higher stage usually points to more flattening. The classification is a tool for doctors, not a diagnosis on its own.

The stages are not always a straight line. Two people with the same diagnosis can show different pictures. A doctor therefore looks at the whole picture, not at one number.

Only a doctor can judge the stages properly, usually with a small piece of tissue from the gut. That is called a biopsy.

From villous atrophy to deficiencies in your blood

Flattened villi have far less surface to absorb food. So deficiencies can arise in iron, vitamin B12, folate and vitamin D. Because the damage often starts in the upper part of the gut, anaemia is sometimes the first signal.

Anaemia from iron deficiency is a known sign of celiac disease (Halfdanarson, 2007). Sometimes it is even the reason someone gets investigated for the first time.

A shortage of vitamin B12 or folate can disturb the making of red blood cells. That can show up as fatigue or paleness.

How iron deficiency develops and which values give insight, you can read in our piece on iron deficiency and anaemia. For the broader approach to vitamin deficiency symptoms, there is a separate article.

Which deficiencies appear exactly differs per person. One person mainly notices fatigue, another mainly breathlessness on exertion.

Vitamin D and calcium can also be absorbed less well with long-term damage. Over time that can affect the bones. Links like these show why celiac disease is more than gut symptoms alone.

Deficiencies are often quiet signals. They build up slowly and sometimes only show up in a blood test.

Do intestinal villi recover?

Yes, villi can very often recover on a gluten-free diet. Once gluten drops away, the inflammation calms and the villi gradually grow back. In adults that recovery can take months to years, and not always fully in everyone (Rubio-Tapia, 2010).

In a large study of adults with celiac disease, the mucosa recovered over time in many people, but not in everyone (Rubio-Tapia, 2010). Consistent gluten-free eating and patience seem to help here.

According to Thuisarts.nl, the Dutch GP information site, the gut can recover once gluten disappears from the diet. In children this often goes faster than in adults.

That capacity to recover is the hopeful part of this story.

Recovery does not mean eating a bit less gluten. Even small amounts can sometimes flare the inflammation again. Many people find that consistently sticking with it makes the difference.

For many people, follow-up with a GP or dietitian is part of the path. That way you keep an eye on how your body responds.

What stands out to me most: the story of villi is one of damage and recovery. The gut has a remarkable ability to renew itself.

Do you have long-term gut complaints or unexplained anaemia? Some people choose to have this checked with a blood test. Read how a celiac disease test works, or go straight to get a celiac disease test with us.

Take the first step today: write down your complaints and discuss them with your GP.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

References

• Dieterich W, et al. Identification of tissue transglutaminase as the autoantigen of celiac disease. Nat Med. 1997. PMID 9212111.
• Rubio-Tapia A, et al. Mucosal recovery and mortality in adults with celiac disease after treatment with a gluten-free diet. Am J Gastroenterol. 2010. PMID 20145607.
• Halfdanarson TR, et al. Hematologic manifestations of celiac disease. Blood. 2007. PMID 16973955.
• Voedingscentrum. Coeliakie en glutenvrij eten.