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Crohn's Disease and Iron Deficiency

Iron is an important component of the blood where it is found in the hemoglobin and supports the oxygen-carrying capacity of red blood cells. However, intestinal bleeding and malabsorption of nutrients can quickly lead to iron deficiency in Crohn’s disease. This article discusses the complications of iron deficiency anemia, its prevalence and diagnosis and also the treatment options available for patients with Crohn’s disease.
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Nutritional Imbalance in Crohn’s Disease

Crohn’s disease is an inflammatory bowel disease caused by impaired innate immunity.

The disease can cause inflammation and lesions in any part of the alimentary canal. However, most patients with Crohn’s disease have inflamed lesions in the colon and the small intestine (especially in the ileum).

The damage done to the mucosal surface of the gastrointestinal tract can severely affect the absorption of nutrients. For example, damage to the ileum may lead to folate and vitamin B12 deficiencies.

Besides damage to the gastrointestinal tract, other presentations of Crohn’s disease may also cause nutritional deficiencies. For example, diarrhea, a common symptom in patients with the disease, can lead to magnesium deficiency.

In addition, prolonged gastrointestinal bleeding can cause iron deficiency in patients with active Crohn’s disease.

The damage to the mucosal surface often leads to intestinal and stomach bleeding. This bleeding is evidenced by the bloody stool passed by some patients.

The risk of gastrointestinal bleeding is also the reason analgesics such as aspirin and ibuprofen are not prescribed for Crohn’s disease patients. These drugs can cause bleeding ulcers in the gut.

Crohn’s Disease, Iron Deficiency and Anemia

When the inflamed mucosal surfaces of the gastrointestinal tract develop into deep ulcers, the internal bleeding that results may appear in stool or not. When the blood released from the ulcerating mucosal does not get into the stool, a condition known as occult bleeding is diagnosed.

However, in severe cases, the bleeding is serious and ongoing and, therefore, appears in the stool.

Continuous blood loss from gastrointestinal bleeding in patients with active Crohn’s disease can significantly lower the level of hemoglobin in systemic circulation.

Hemoglobin is the oxygen-carrying portion of red blood cells. It is rich in iron and its functions are dependent on this mineral.

When hemoglobin level falls in the body, it causes anemia and iron deficiency.

Although blood stool is indicative of anemia in Crohn’s disease patients and usually reason enough to begin iron supplementation, doctors still need to order some tests to diagnose anemia.

Diagnostic Tests for Anemia in Crohn’s Disease
  • Complete blood count to measure hemoglobin level and hematocrit
  • Fecal occult blood test
  • Colonoscopy
  • Upper gastrointestinal endoscopy

Diagnosing Anemia in Crohn’s Disease

Hemoglobin level

Most of the iron stored in the blood is found in the hemoglobin of the red blood cell. Therefore, a low hemoglobin level indicates iron deficiency anemia.

For males, the normal range of hemoglobin level is 14 – 18 g/dl and 12 – 16 g/dl for females.

Hematocrit

The hematocrit is the portion of the blood made up by red blood cells. Therefore, measuring hematocrit level is another way of determining iron levels.

The normal range of hematocrit is 32 – 43%. In Crohn’s disease, anemia can cause hematocrit level to drop well below this range.

Other parameters measured when taking a complete blood count include the number and size of red blood cells. During iron deficiency anemia, the body produces fewer red blood cells and these are smaller than normal red blood cells.

Fecal occult blood test

The fecal occult blood test is used to investigate signs of internal bleeding. Essentially, it involves your looking for signs of blood in your stool.

Once blood is detected in the stool of a patient with Crohn’s disease, the doctor will use the test discussed below to find the source of the bleeding.

Colonoscopy

A colonoscopy is a means of visually examining deep into the colon. It requires the insertion of a thin, flexible tube with a video camera attached at the end into the anus to see the lower end of the gastrointestinal tract.

With it, a doctor can get a good peek inside the colon and discover the site of the bleeding and the nature of the inflamed lesions or ulcers causing it.

Upper gastrointestinal endoscopy

An upper GI endoscopy is similar to a colonoscopy except the thin, flexible tube with camera is inserted through the mouth.

This kind of endoscopy is used to examine the stomach and upper intestine for signs of bleeding.

Treating Iron Deficiency Anemia in Crohn’s Disease

Before low iron levels become severe iron deficiency, patients with Crohn’s disease should include more iron-rich foods in their diets.

As long as diarrhea is not present, dietary and supplemental sources of iron can help raise blood iron levels.

Food sources of iron include plants such as lentils and soybeans as well as meat. Meat contains heme while plants are non-heme sources of iron. Heme iron is more readily absorbed in the body than plant-sourced iron. This is the reason why iron deficiency is more common among vegetarians.

However, consuming vitamin C-rich foods (or taking vitamin C supplements) can improve absorption of non-heme iron.

Dietary Sources of Iron
  • Clam
  • Pork liver
  • Lamb kidney
  • Beef
  • Soybeans
  • Lentils
  • Spinach

Iron supplements may be recommended after iron deficiency anemia has been diagnosed. The recommended dose of these supplements is 325 mg taken 1 – 3 times daily.

In severe cases of anemia caused by extensive blood loss, patients with Crohn’s disease may be given iron injections and even blood transfusions.

The common forms of iron in over-the-counter iron supplements are ferrous and ferric. The ferrous form is more easily absorbed.

Iron supplementation should be closely monitored especially in children with Crohn’s disease.

Free iron in the blood is toxic and high dose of iron supplements can cause cramping, constipation and black stool.

Studies on Iron and Crohn’s Disease

Prevalence and Diagnosis of Iron Deficiency in Crohn’s Disease

In a 1978 study published in the journal, The American Journal of Digestive Diseases, a group of researchers determined the prevalence of iron-deficiency anemia among 105 patients with inflammatory bowel disease.

Out of this pool of participants, 64 patients had Crohn’s disease while 41 patients suffered from ulcerative colitis.

The researchers found out that 36% of the ulcerative colitis patients and 22% of the Crohn’s disease patients suffered from iron deficiency. In addition, 32% of the former and 2% of the latter suffered from impaired erythropoiesis (impaired red blood cell production).

Among the Crohn’s disease patients, 51% had anemia even though the iron store in their bone marrows were normal.

The researchers found out that measuring serum ferritin was the best way to predict iron deficiency among patients with inflammatory bowel disease.

A 1973 study published in the journal, Gut, also reached similar conclusions.

The researchers found out that although most patients with Crohn’s disease present with symptoms of iron deficiency, only half of them have sub-optimal iron stores in their bone marrows. Therefore, true iron deficiency is only about half as common in Crohn’s disease patients as routinely believed.

Of the laboratory techniques used to determine iron deficiency, the researchers believed that total iron-binding capacity or TIBC is the most useful.

In conclusion, the researchers stated that the impaired production of red blood cells caused by iron deficiency in Crohn’s disease patients is most likely due to the extensive inflammation characterizing the disease.

Lastly, the authors of the study recommended the examination of bone marrow samples to fully diagnose iron deficiency in Crohn’s disease.

Dietary Iron Intake and Crohn’s Disease

A 2004 study published in the British Journal of Nutrition investigated the link between iron intake and dietary changes among Crohn’s disease patients.

Earlier and preliminary studies indicated that people with Crohn’s disease usually change their diets to help relieve abdominal symptoms. The new diets may interfere with iron absorption and cause low iron intake.

The study involved 91 patients with Crohn’s disease and another 91 healthy controls.

By studying their food consumption over a week, the researchers found out that fewer patients than controls met the recommended daily iron intake.

From the food diaries kept by the study’s participants, the researchers found that the reason for lower dietary iron intake among patients with Crohn’s disease is adoption of low-fiber breakfast cereals that were not fortified with iron.

While low-fiber diets may reduce abdominal pain and the chances of renewed internal bleeding in the gastrointestinal tract, they can lead to low iron levels in patients and increase the risks of iron deficiency and anemia.

Therefore, the researchers recommended that iron supplements may be needed to make up for the low iron content of recommended Crohn’s disease diets.

Iron Absorption in Crohn’s Disease

A 2006 study published in the journal, Inflammatory Bowel Diseases, investigated the effect of inflammation on iron absorption in Crohn’s disease.

For this study, the researchers recruited 19 participants with active and inactive Crohn’s disease.

For each patient, the researchers measured serum iron and hemoglobin levels as well as markers of inflammation after an overnight fast.

The results showed that the participants with active Crohn’s disease had impaired oral iron absorption while those with inactive disease had normal iron absorption.

In addition, inflammatory markers especially the interleukin, IL-6, were higher in participants with active disease.

These results suggest that iron deficiency in Crohn’s disease is most likely linked to inflammation in the gastrointestinal tract. Therefore, the inflamed lesions in the intestines may reduce iron absorption.

The researchers concluded that oral iron supplementation may only have limited benefits in patients with active Crohn’s disease.

Iron Deficiency in Children with Crohn’s Disease

The causes and impact of iron deficiency in children with Crohn’s disease were the subjects of a 1992 study published in the Journal of Pediatric Gastroenterology and Nutrition.

The study involved 199 children with various gastrointestinal diseases including celiac disease, milk intolerance, giardiasis, diarrhea, enteritis and Crohn’s disease. The researchers measured the different indices of iron status including total blood count, hematocrit, serum ferritin and transferrin saturation.

The results showed that iron deficiency was common (prevalence of 72%) among children with Crohn’s disease. Also common were intestinal blood loss and iron malabsorption.

The researchers concluded that impaired iron absorption was the major cause of iron deficiency among children with Crohn’s disease.

Oral Iron vs. Iron Injections

Oral iron supplements are routinely prescribed for patients with Crohn’s disease to help restore serum iron levels and treat iron deficiency anemia. However, there are concerns that iron supplementation may worsen the symptoms of Crohn’s disease.

In a 2010 study published in the journal, Gut, a group of researchers investigated the effects of iron in gastrointestinal tract damaged by Crohn’s disease.

For the study, the researchers used mice and induced a Crohn’s disease-like condition known as ileitis in them. Thereafter, they were divided into 2 groups. Over a period of 11 weeks, one group was fed with a diet rich in iron sulfate while the other group got an iron sulfate-free diet but received iron injections.

By monitoring markers of inflammation and disease activity throughout the period of the study, the researchers determined that oral iron supplementation triggered the kind of inflammation associated with Crohn’s disease.

In contrast, the mice given iron injection got better, had no signs of inflammation and were not iron deficient.

Management of Iron Deficiency in Crohn’s Disease

A 2007 paper published in the journal, Inflammatory Bowel Diseases, provided a comprehensive set of guidelines for the diagnosis and management of iron deficiency and anemia in inflammatory bowel diseases.

Some of the study’s results were especially revealing. For example, the researchers identified the various causes of anemia in Crohn’s disease as well as their frequencies.

Causes of Anemia in Crohn’s Disease

Common Causes

  • Iron deficiency
  • Intestinal bleeding

Occasional Causes

  • Vitamin B12 deficiency
  • Folate deficiency
  • Drug-induced impairment of iron/B vitamin absorption and distribution

Rare Causes

  • Genetic disorders of blood cell formation or hemoglobin function
  • Drug-induced organ failure
  • Destruction of red blood cells

The study also identified the specific interventions needed to address iron deficiency and anemia in patients with Crohn’s disease.

The researchers recommended that iron supplementation should begin as soon as iron deficiency anemia has been diagnosed. However, anemia without iron deficiency does not need iron supplementation. In such cases, supplementation with vitamin B12 and folic acid may be required to treat the anemia.

The study also concluded that oral iron supplements are the simplest and first consideration in the treatment of iron deficiency anemia.

The researchers identified that the ferrous iron left unabsorbed in the gastrointestinal tract follow oral iron supplementation may worsen Crohn’s disease by aggravating inflammation in the intestine.

While iron injection may be the better choice in order to avoid worsening the symptoms of Crohn’s disease, it also carries the risk of anaphylactic shock induced by dextran found in intravenous iron preparations.

Lastly, the study showed that erythropoietic therapy (for increasing the population of red blood cells) should be initiated when intravenous iron therapy fails to reverse iron deficiency anemia after 4 weeks or if hemoglobin level falls below 10 g/dL.

Significant blood loss due to gastrointestinal bleeding may require blood transfusion but there is still a need to replace iron or boost the production of red blood cells.

Sources


http://www.netdoctor.co.uk/diseases/facts/crohnsdisease.htm

http://www.health.com/health/gallery/0,,20562810_2,00.html

https://www.quest4health.com/imported/Anemia/Anemia_due_to_chronic_diseases/Article/How-does-anemia-occur-in-crohns_disease_article_ver1.0

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