Iron deficiency is one of the most common signs of celiac disease—in all likelihood, you also had a deficiency when your celiac disease was diagnosed. Therefore, there are many questions on this topic, especially regarding how the deficiency can best be corrected and why it keeps recurring in some patients. I have looked into these issues and have compiled the most important information for you below.

Why does our body need iron?

Iron is primarily important for enabling our blood to transport oxygen. The red blood pigment hemoglobin absorbs oxygen in the lungs, binds it, and uses red blood cells (erythrocytes) to carry it to our body's cells. However, numerous other processes, including the immune system, also require iron to function correctly.

New red blood cells are formed every day, and our body needs 20–30 mg of iron daily for this purpose. However, the body only absorbs about 1–2 mg from food through the intestines. This is because too much iron is not useful and can even be harmful. The body protects itself against excessive intake because it cannot actively excrete an "excess" of iron.

However, we are very efficient at recycling the iron that is released during the breakdown of old erythrocytes, meaning that in most cases, we only actually need that small amount that the intestines absorb from food.

So, how does the deficiency occur?

If more iron is consistently lost than is absorbed, the stores we have, primarily in the liver, gradually become depleted over time. Once these stores are empty, the deficiency also affects blood formation: fewer and smaller red blood cells are produced. This leads to anemia. Since women repeatedly lose blood—and therefore iron—due to menstruation, their hemoglobin levels are lower than those of men.

How does a deficiency occur in celiac disease?

Depending on the study, 12 - 85% of people with celiac disease have an iron deficiency, and about half of those affected have anemia. Iron deficiency can also be the only sign of celiac disease. Therefore, it should always be considered when there is no other clear cause for it. In more than 10% of people with iron deficiency who do not respond to supplemental iron preparations, the underlying cause is celiac disease. Iron is primarily absorbed in the duodenum – exactly where the most inflammation and mucosal impairment occur in celiac disease. The flattened mucosa provides a significantly smaller surface area for the absorption of nutrients. Celiac patients with iron deficiency anemia often have higher levels of celiac antibodies, greater villous atrophy, as well as lower body weight and poorer bone density. All of this points to a generally more severe course of the disease.

Anemia can be further exacerbated if folic acid and vitamin B12 are not absorbed sufficiently, as both vitamins are also necessary for blood formation. Folic acid, like iron, is absorbed in the upper small intestine, and 20 - 30% have a deficiency at the time of diagnosis. Although vitamin B12 is only absorbed at the end of the long small intestine, 8 - 40% of celiac patients show a deficiency here as well.

A third reason is the chronic inflammation present in the body with celiac disease. This not only affects the intestine, but the inflammatory markers can lead to changes in metabolic processes throughout the entire body. In terms of iron metabolism, they prevent the release of stored iron from the intestinal mucosa and liver cells and reduce the absorption of iron from food.

How do you know if you have an iron deficiency?

Typically, this iron deficiency manifests itself through headaches, fatigue, lethargy, and exhaustion. In children, it can lead to developmental delays, both psychomotor and mental. Hair loss, brittle fingernails, cracking at the corners of the mouth, susceptibility to infections, and a burning tongue are other possible effects. In cases of severe anemia, a rapid heartbeat or even shortness of breath may occur because too little oxygen is being transported in the blood. Many people feel the effects of an iron deficiency well before anemia sets in, because the iron content in individual cells drops beforehand, thereby causing symptoms.

How is an iron deficiency detected?

This is an important question, because unfortunately the correct test is often not performed. Many people are tested for free iron in the blood. However, this is not very informative, as it constantly changes throughout the day and due to other external factors. In quite a few affected individuals, the deficiency is noticed due to the onset of anemia: the red blood cells are too small (MCV value below 80 fl) and the hemoglobin level (Hb value) is too low. To detect an iron deficiency earlier, the ferritin value is a good parameter. If it is too low, it indicates an iron deficiency. According to the WHO, this is the case with a value below 15 mg/l. Others assume a deficit starting at a value below 30 mg/l. If the ferritin value is normal or even elevated, this does not rule out a deficiency. This is because if there is a chronic inflammation or severe infection, the ferritin also rises as a result. Therefore, the inflammation marker CRP should always be tested at the same time. If this is elevated, other tests for iron metabolism should be used. Incidentally, celiac disease usually does not trigger elevated CRP values, even though a chronic inflammation is present.

Another, albeit more expensive, option is the examination of the soluble transferrin receptor (sTfR). This value is independent of inflammation and can therefore detect a deficiency very reliably.

How can you fix your iron deficiency?

Diet with iron-rich foods

The first thing that certainly comes to mind is incorporating more foods with a higher iron content into your diet. This is fundamentally a very good idea, even for the long term, to ensure the body has enough iron available. It is also the most natural method, allowing the body to decide for itself how much it wants to absorb. However, correcting an iron deficiency takes quite a long time this way, as iron absorption is, as already mentioned, very limited. During this time, symptoms would not improve very quickly either.

Dietary supplements

To replenish iron stores more quickly, dietary supplements or medically prescribed medications are often used. It is actually sensible to wait about 3 months after switching to a gluten-free diet, as the inflamed mucous membrane does not absorb iron at all. And the flattening of the mucous membrane plays a role as long as it persists. Iron supplements taken as tablets or liquid can also cause side effects in some people, such as abdominal pain, constipation, or loss of appetite. This means there is a large overlap with the symptoms of celiac disease. Consequently, it is difficult to distinguish what is triggering the symptoms or whether celiac symptoms are improving with a gluten-free diet. However, you can influence this by choosing the right preparation: supplements with iron gluconate have fewer side effects than those with ferrous sulfate. Newer formulations such as so-called sucrosomial iron are also better tolerated. In this case, the iron is particularly well "packaged," causing fewer digestive complaints.

Iron infusions

A third alternative is iron infusions. This is used especially when there is severe anemia that must be corrected quickly. With the infusion, the iron bypasses the intestine, enters the body directly, and can be utilized. Today's infusion preparations are significantly better tolerated than those in the past. Since they often had strong side effects, iron infusions are still administered rather reluctantly. Nevertheless, there are situations in which it represents the best option.

What could be the reason for recurring iron deficiency?

While many affected individuals recover well from iron deficiency through therapy and a gluten-free diet, about half still show signs of anemia after one year. There are several possible reasons for this:

• The mucous membrane has not yet sufficiently recovered, which is common in adults. This impairs iron absorption in the gut. You should review your gluten-free diet to see if any hidden sources of gluten are still present. A nutritionist can help determine if your diet contains enough iron and if it is being absorbed effectively. Beverages like tea and coffee, as well as calcium and certain dietary fibers, hinder iron absorption. Furthermore, plant-based (non-heme) iron is absorbed less efficiently than animal-based (heme) iron. In this case, a glass of orange juice (or another source of Vitamin C) or even meat with your meal can help improve the absorption of plant-based iron.

• As long as there is inflammation in the mucous membrane or anywhere in the body, less iron is absorbed from the gut, and its release from storage is also reduced.

• In cases of persistent or recurring anemia, it should be investigated whether there is hidden blood loss in the body, for example in the abdomen, urinary tract, or, in women, due to gynecological causes.

• What is often overlooked are tiny changes on the surface of the intestinal lining cells (epithelial cells). Each individual cell has a so-called brush border, which further increases the absorptive surface area. These ultrastructural and molecular changes can—if at all—only be seen with an electron microscope. However, this is ultimately only available for research purposes and is not a routine examination.

• Genetic factors can also affect proteins in iron metabolism in a way that impairs iron absorption. This would be independent of celiac disease.

Iron metabolism in our body is a very complex process, so I would like to summarize the most important aspects for you, especially in relation to celiac disease: