Celiac disease damages the part of the gut that absorbs most nutrients. That means deficiencies can show up even when a person eats a balanced diet. I'm a mom, not a clinician, so this is what I've learned from reading about celiac nutrition and from living in a gluten-free kitchen. It is education, not medical advice.

What happens inside the small intestine

Celiac disease is an autoimmune condition, not an allergy or intolerance. In response to gluten, the immune system attacks the villi, the tiny finger-like projections that line the small intestine. Think of those villi like a shag carpet. The soft fibers grab nutrients from food as it passes through. Over time the attacks cause the villi to flatten or blunt. Less surface area means fewer nutrients get pulled into the bloodstream. That process is called malabsorption.

Common nutrient deficiencies with celiac disease

The nutrients that come up repeatedly in celiac nutrition guidance are iron, vitamin D, calcium, folate, vitamin B12, and zinc. Fat-soluble vitamins A, E, and K also run low when fat absorption is off.

• Iron: low iron leads to anemia, fatigue, shortness of breath, and brain fog. Iron is absorbed in the upper small intestine, which is often the first area affected.
• Vitamin D and calcium: both support bone health, and low levels often cause no obvious symptoms until a bone density scan shows a problem.
• Folate and vitamin B12: both are involved in red blood cell production. Low levels add to anemia and make tiredness worse.
• Zinc: plays a role in immune function, wound healing, and taste. Deficiency sometimes shows up as poor appetite or slow healing.
• Fat-soluble vitamins A, E, and K: when the gut can't absorb fat well, these vitamins go with it.

This list is not a checklist to self-diagnose. Symptoms overlap with many other conditions. Your doctor checks nutrient levels with blood work, not by matching symptoms to a list.

Why deficiencies can continue after going gluten-free

Going gluten-free is the first step, but it does not flip a switch. The villi need time to heal. While they are healing, absorption remains limited. That is why doctors often recheck nutrient labs months after diagnosis, not only at the first appointment.

Dairy can be tricky early on too. Lactase, the enzyme that breaks down dairy sugar, is made at the tips of the villi. When those tips are damaged, some people become temporarily lactose intolerant. That affects calcium and vitamin D intake, especially if dairy was a main source.

Cross-contact matters too. If small amounts of gluten keep sneaking in through shared cutting boards, toasters, or seasonings, the immune response keeps the gut inflamed. The lining heals more slowly. That is why label reading and a dedicated gluten-free kitchen setup reduce the chance of repeated exposure.

What to ask your doctor or dietitian

When I first learned about this, my biggest shift was understanding that supplements are not a default. Some nutrients, like iron and fat-soluble vitamins, build up in the body if you take them without a known deficiency. Testing first is the safer path. A celiac-informed dietitian can help sort out which foods to add and which supplements, if any, fit your labs and your history.

For iron, that might mean cooking in cast iron, pairing beans or meat with vitamin C from peppers or citrus, and adding leafy greens. For calcium without dairy, fortified plant milks, tofu processed with calcium sulfate, and canned fish with bones help. For vitamin D, fatty fish and fortified foods are common sources, though many people need a supplement based on their labs.

I don't list doses or specific supplement brands because those depend on your own blood work and medical history. That is a conversation for you and your doctor.

Small kitchen swaps that make label reading easier

For our family, one practical piece of healing has been knowing what is in the seasonings and pantry staples we use every week. Bouillon, soup mixes, and spice blends hide gluten, dairy, or soy. I read every label, and I keep a short list of trusted products. Clean Monday Meals seasonings and bouillon are gluten-free, dairy-free, and soy-free, with no fillers or artificial flavors, so I can use them in soups, rice, and ramen without pausing to decode the label.

That isn't a replacement for medical care. It is one less variable in a process that already has enough variables.

To bring it back to the question: celiac disease affects nutrient absorption by damaging the villi that do the absorbing. That is why iron, vitamin D, calcium, folate, B12, and zinc are the nutrients your care team will watch. Healing takes time, labs matter more than symptoms, and you don't have to figure it out all alone. If you are newly diagnosed or supporting a child through this, start with a doctor or dietitian who understands celiac, and keep asking questions. You are doing better than you think.