Iron deficiency is a condition of insufficient iron stores within the body. Iron deficiency anaemia occurs when the condition reaches the point that it begins to reduce the production (or number) of red blood cells (RBCs).
Iron is involved in the production of RBCs and plays a vital role in helping them transport oxygen throughout the body. Iron deficiency occurs when iron losses, or physiological requirements for iron, exceed the amount of iron absorbed by an individual.
Commonly, people attribute a diagnosis of iron deficiency to an individual’s lack of dietary iron intake. However, there are several other possible causative factors of iron deficiency, including the following.
Excessive blood loss most typically occurs due to some degree of physical trauma, including injury and internal trauma/ bleeding. Infection with intestinal parasites can cause blood loss through the gastrointestinal tract. In females, monthly menstrual bleeds are an unavoidable cause of blood loss and are of particular concern where the menstrual bleeds are heavy or prolonged.
Malabsorption of iron is caused by an apparent reduction in the absorptive capabilities of the gastrointestinal tract mucosa. This may be a result of damage to the gastrointestinal tract mucosa or due to exogenous agents that bind to iron in the gastrointestinal tract and inhibit their bioavailability (ability to be absorbed). Examples of exogenous agents that inhibit the bioavailability of iron include compounds such as tannins and some medications, including antibiotics.
Malabsorption of iron may also be caused by low stomach acid levels. High levels of stomach acid create an acidic environment within the stomach which enhances the solubility and therefore absorption of iron through the gastrointestinal mucosa. Furthermore, a number of nutritional co-factors are required for the gastrointestinal absorption of iron, including vitamin C. Where there is a lack of nutritional co-factors available, iron absorption is reduced.
In some circumstances, certain individuals may have an increased physiological demand for iron. Most commonly we see this in pregnancy, where the demand for iron increases significantly due to the expansion of maternal RBCs and foetal growth. Increased physiological demand for iron is also typically seen in elite athletes due to their high training (exercise) load. High training loads stimulate an increase in RBCs within the body, which increases the demand for iron.
During infection, one of the body’s non-specific defence mechanisms to inhibit pathogenic bacteria growth is to reduce serum iron levels. In response to infection, the body’s temperature rises and, subsequently, serum iron levels drop. Once the body’s temperature is raised to ‘fever’ level and iron levels have dropped low enough, the growth of pathogenic bacteria is inhibited. Therefore, ongoing or chronic infections can negatively impact an individual’s iron levels.
Typical signs and symptoms of iron deficiency include:
- fatigue or extreme fatigue
- pale skin and mucous membranes
- shortness of breath
- irregular heartbeat
- intolerance to cold
- cold hands and feet
- poor concentration
- impaired cognitive function
- dizziness and lightheadedness
- brittle nails.
In the case of suspected iron deficiency or iron deficiency anaemia, it is important to conduct thorough investigation through pathology testing. Routinely, individuals will be sent for ‘iron studies’, which are a set of tests that measure different aspects of iron in the body. Some of these are outlined below.
A serum iron test measures how much iron is in the serum (liquid component) of the blood.
Ferritin is a protein that stores iron. A ferritin test measures the amount of iron stored in the body, or more specifically the liver.
Transferrin or Total Iron Binding Capacity (TIBC)
Transferrin is the main protein that transports iron throughout the body. A transferrin or TIBC test measures how much and how well the body transports iron. Your body makes transferrin in relation to your need for iron. When iron stores (ferritin) are low, transferrin levels increase.
Transferrin saturation is a calculation between serum iron and transferrin or TIBC that represents the percentage of transferrin that is saturated with iron.
While iron studies are most helpful in determining iron deficiency, in addition, individuals will typically also be sent for a ‘Full Blood Count’, which helps to further determine or rule out iron deficiency anaemia.
Where a diagnosis of iron deficiency or iron deficiency anaemia is made, treatment will depend largely on the cause and severity of iron deficiency. However, almost always treatment of iron deficiency and iron deficiency anaemia will include dietary modifications (increasing iron-rich foods and co-factors for absorption) and iron supplementation.
Heme vs. non-heme iron
The iron obtained from our diets comes in two main forms: heme and non-heme iron. Heme iron comes from animal-based sources, such as beef, pork, chicken, kangaroo, lamb, seafood and other meats. Non-heme iron comes from all other food sources, typically plant-based sources, such as leafy green vegetables, beans and other legumes, nuts and seeds etc. Generally speaking, non-heme iron sources are less bioavailable and not as easily absorbed in the gastrointestinal tract as heme iron sources. For this reason, it is recommended that individuals combine heme and non-heme iron sources where possible.
The tables below list examples of heme and non-heme iron sources and their iron content based on typical serving sizes. The recommended dietary intake (RDI) of iron for adult males is 20 mg per day and adult females is 18 mg per day.
Non-Heme Sources of Iron
|Serving Size||Iron Content|
|Kidney beans||1 cup||3.1mg|
|Green lentils||1 cup||3mg|
Heme Sources of Iron
|Food Source||Serving Size||Iron Content|
In addition to increasing heme and non-heme iron sources in the diet, there are several other dietary modifications that can be made to help maximise the absorption of iron in the gastrointestinal tract, including:
- combining heme and non-heme sources of iron (see above)
- consuming vitamin C-rich foods together with iron-rich foods. Vitamin C enhances the body’s absorption of iron.
- consuming any dairy products away from iron-rich foods and meals. Calcium found in dairy competes or interferes with the absorption of iron in the gastrointestinal tract.
- avoiding the consumption of tea/coffee close to main meals. Certain constituents in tea and coffee can inhibit the absorption of iron in the stomach.
- cooking non-heme sources of iron. This increases the bioavailability of the iron.
- cooking in cast iron cookware. Iron from the cookware leaches into the food, boosting the iron content of the food.
In most cases of iron deficiency and iron deficiency anaemia, iron supplements will be recommended or prescribed. Iron supplements vary in terms of the ‘form’ of iron and the amount of iron they contain, and thus it is important to speak with your health care practitioner about which iron supplement is best for you. There are certain risks associated with taking iron supplements where iron deficiency is absent and therefore it is advised that they only be taken under the supervision of a medical or qualified health practitioner.
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Written by Perri Baldwin BHSc