domingo, 22 de diciembre de 2019

Causes of Anemia

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By Dr. Ananya Mandal, MDReviewed by Sally Robertson, B.Sc.

Anemia is a blood disorder characterized by an inadequate level of hemoglobin in the blood. Hemoglobin is needed to transport oxygen around the body. It is a protein that enables red blood cells to carry oxygen from the lungs to tissues and other organs in the body and to transport carbon dioxide to the lungs from other parts of the body so it can be expelled.

Mechanisms of Anemia

There are several types of anemia; some only cause mild health problems, while others are much more serious. Whichever type of anemia a person has, the condition is caused by one of the following:

The body fails to produce adequate levels of hemoglobin
Hemoglobin is produced, but it fails to function properly
The body does not produce adequate levels of erythrocytes (red blood cells)
Erythrocytes are broken down too quickly in the body

Iron-Deficiency Anemia

Hemoglobin and red blood cells are made by the bone marrow, which requires iron in order to produce them. If iron is lacking, the bone marrow cannot make hemoglobin for red blood cells. The most common cause of anemia is a lack of iron. Reasons why the body’s iron stores may be depleted include the following:

Blood Loss

When a person loses blood as a result of surgery, injury, a blood clotting disorder such as hemophilia or intestinal bleeding caused by an ulcer or cancer, then anemia may develop. The use of blood thinners such as aspirin or heparin can also lead to anemia.

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) can also lead to stomach ulcers and chronic intestinal bleeding. For women, menstruation is another risk factor for blood loss.

Diet Lacking in Iron

For the body to produce adequate levels of hemoglobin, the diet needs to be rich enough in iron. Good sources of iron include wholewheat bread, kidney beans, tofu, tuna, eggs, shrimps, turkey leg, brown rice and leg-of-lamb.

Pregnancy

An unborn baby is reliant on the mother for iron, meaning the level of iron the body needs is increased during pregnancy. Many women therefore take a vitamin supplement that contains iron to decrease the risk of anemia developing.

Vitamin Deficiency Anemia

Aside from iron, the body also requires vitamin B12 and folate to produce red blood cells and hemoglobin. A diet low in levels of these nutrients can decrease the body’s ability to produce healthy erythrocytes that have enough hemoglobin in them. In the majority of cases, people with vitamin B12 or folate deficiency have erythrocytes that are large, underdeveloped and fail to function properly. This is also referred to as megaloblastic anemia.

Foods that are a good source of B12 include meat, fish and dairy products and a diet that includes these is usually adequate to ensure adequate B12 levels. People with a poor overall diet or those following a vegan diet may be at risk of vitamin B12 deficiency anemia.

Examples of foods that are good sources of folate are broccoli, asparagus, chickpeas and brown rice. A folate deficiency may develop if these foods are not eaten regularly.

Other factors that can lead to vitamin B12 or folate deficiency anemia are described below:

Other Causes of Vitamin B12 Deficiency

Pernicious anemia – Some individuals do consume adequate levels of B12, but cannot process the vitamin due to an autoimmune condition called pernicious anemia. Here, the body’s immune system attacks cells in the stomach that produce a protein called intrinsic factor. Intrinsic factor combines with vitamin B12 to form a complex that is then absorbed by the gut. The lack of intrinsic factor seen in pernicious anemia prevents this absorption of vitamin B12. Pernicious anaemia is the most common cause of vitamin B12 deficiency in the UK.

Conditions Affecting the Stomach and Intestine

Certain stomach and bowel conditions or surgeries can affect the body’s ability to absorb sufficient amounts of vitamin B12. An example of such a condition is the inflammatory bowel condition Chron’s disease and an example of such as surgery is gastrectomy – where part of the stomach is removed. Anemia caused by Chron’s disease or other chronic conditions such as kidney disease or cancer is referred to as anemia of chronic disease.

The Use of Certain Medications

Some medications can affect the absorption of B12. Proton pump inhibitors (PPIs), for example, inhibit the production of acid in the stomach. Without this acid, vitamin B12 cannot be released from food in the stomach.

Other Causes of Folate Deficiency Anemia

Malabsorption

Certain health conditions can affect the body’s ability to absorb folate properly. An example of such as condition is a disease of the digestive system called Celiac disease.

Excessive urination

Excessive urination can lead to too much folate being expelled from the body. Examples of problems that can lead to excessive urination include acute liver damage and congestive heart failure.

Medication

Certain medications decrease folate levels or affect the body’s ability to absorb it. One examples is certain types of anticonvulsants used to treat epilepsy.

Need for excess folate

In some circumstances, the body requires more folate than it usually would which can lead to folate deficiency anemia if this excess need is not met. Examples include pregnancy, having a blood disorder, having cancer and having a condition that causes inflammation.

Aplastic Anemia

Aplastic anemia is a condition that decreases the amount of red blood cells because the bone marrow has become damaged and incapable of making adequate amounts of new blood cells. This may be caused by a viral infection, the use of certain medications such as cancer drugs or antibiotics and exposure to some toxic substances. Leukemia and autoimmune diseases also affect the bone marrow’s ability to make red blood cells.

Hemolytic Anemias

Hemolytic anemia is a condition where red blood cells do not last as long as they usually would, which is about 120 days. The bone marrow does not produce enough red blood cells at a fast enough rate to replace the ones being destroyed. Factors that can lead to re blood cell destruction include autoimmune disorders, genetic conditions such as sickle cell anemia and thalassemia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, blood clots, infection and exposure to certain medications, chemicals or toxins.