Anaemia is when you have a lower-than-normal number of red blood cells in your blood. The most common cause of anaemia is not having enough iron available to make red blood cells (iron deficiency).
Iron deficiency is the most common dietary deficiency in the world and typically causes fatigue and weakness. It mainly affects children and women (particularly pregnant women).
In New Zealand, studies suggest that about 10% of women (compared with 1% of men) and 14% of infants and toddlers have iron deficiency, a proportion of whom will show signs of anaemia.
Red blood cells perform the important task of carrying oxygen (attached to a protein called haemoglobin or ‘haem’) around the body. Anaemia can occur as the result of reduced production, or an increased loss, of red blood cells.
The body requires three essential elements – iron, vitamin B12, and folic acid – to produce red blood cells.
The main causes of iron deficiency anaemia are:
- blood loss
- insufficient iron in the diet
- poor absorption of dietary iron from the digestive tract
Babies are born with sufficient iron supplies to last for approximately six months of feeding with milk (breast or formula) alone. After this time babies need iron rich or fortified foods gradually added to their diets to meet their bodies' iron requirements.
Children and teenagers go through spurts of rapid growth, which require a great deal of iron. A balanced diet with adequate amounts of iron is important at these times.
Iron deficiency anaemia occurs frequently among women of childbearing age. In women who are not pregnant the cause may be due to heavy loss of blood during menstruation. In pregnant women, iron stores have to serve the increased blood volume of the mother, as well as the needs of the growing baby. If sufficient iron intake is not maintained (either in the diet or in the form of iron supplements), the body can become deficient in iron over time, eventually leading to iron deficiency anaemia.
In adults, iron deficiency anaemia can occur as the result of blood loss from the digestive tract arising from long-term use of some medications (such as aspirin and NSAIDs), gastric ulcers, duodenal ulcers or bowel cancer. Bowel screening is offered free for people aged 60–74 years to detect bowel cancer at an early stage when treatment is more likely to be successful (for more information call free on 0800 924 432).
Conditions that affect the absorption of iron by the digestive tract – such as coeliac disease (gluten intolerance) and Crohn's disease – and conditions that cause chronic inflammation – such as systemic lupus erythematosus and rheumatoid arthritis – may also lead to iron deficiency.
Signs and symptoms
The symptoms of iron deficiency anaemia become apparent once the body's stores of iron have been depleted. Symptoms tend to appear gradually and may include:
- paleness of the skin, gums, and nail beds
- reduced ability to fight infections
- an inflamed and sore tongue that has a smooth shiny appearance
- difficulty concentrating
- shortness of breath when exercising
- angina (heart related chest pain).
Changes to the hair and skin, and abnormal growth of the fingernails, may occur in cases of severe iron deficiency. There may also be dryness of the mouth and throat, and inflammation of the tongue. Long-term iron deficiency may lead to developmental and learning problems in children.
An assessment of symptoms and blood tests are used to diagnose iron deficiency anaemia. Blood tests will determine the number, size, and colour of red blood cells, haemoglobin level, and the iron stores in the body. When it is suspected that there is blood loss from the digestive tract, tests to detect blood in the bowel motions may be recommended. Diagnostic tests (e.g., colonoscopy, gastroscopy) to investigate the digestive tract for the source of any blood loss may be performed. It is important that the underlying cause of the deficiency is identified, as iron deficiency may be the first symptom of a more serious disorder.
Dietary supplements containing iron in tablet or liquid form and/or a change in diet may be recommended. Taking iron supplements for several months or longer may be required to replenish iron stores.
In people whose iron deficiency is severe, intravenous iron infusions or a transfusion of red blood cells is used for rapid replacement of iron and haemoglobin.
However, treatment of iron deficiency anaemia appears to be shifting to increased use of intravenous therapies since they provide rapid iron repletion with fewer adverse effects relative to oral therapies.
Other treatment may be recommended depending on the underlying cause of the deficiency (e.g., medication or surgery if blood loss from the digestive tract is the underlying reason for iron deficiency).
The risk of developing iron deficiency anaemia can be reduced by having sufficient iron in the diet. There are two main types of dietary iron: haem iron and non-haem iron.
Haem iron is readily absorbed by the body and is found in liver, red meat, chicken, and fish.
Non-haem iron is not so easily absorbed and is found in whole grain cereals, leafy green vegetables, fruits, nuts, and peas, beans, and lentils. To assist the body to absorb non-haem iron more easily:
- include a source of vitamin C with a meal
- consume meat with non-haem iron food
- avoid tea and coffee at mealtimes.
The recommended daily dietary intake of iron is:
- Infants 7–11 months: 11mg
- Children 1–8 years: 9–10mg
- Children 9–13 years: 8mg
- Teenage girls 14–18 years: 15mg
- Teenage boys 14–18 years: 11mg
- Women 19–50 years: 18mg
- Pregnant women 14–50 years: 27mg
- Breastfeeding women 14–50 years: 9–10mg
- Women over 50 years: 8mg
- Men over 19 years: 8mg
To put these quantities in perspective, a 250g beef steak may contain around 10mg of iron, a baked potato with skin around 2mg, and a chicken leg between 1 and 2mg. Eating plenty of foods that contain iron is particularly important for children and pregnant or menstruating women.
People who are strict vegetarians (particularly vegans) and people on weight reduction diets or rigorous exercise programmes also need to make sure they are getting a good source of iron in their dietary intake and/or in the form of iron supplements.
Elstrott, B., et al. The role of iron repletion in adult iron deficiency anemia and other diseases. Eur J Haematol. 2020 Mar;104(3):153-161.
Grant, C.C., et al. (2007). Population prevalence and risk factors for iron deficiency in Auckland, New Zealand. J Paediatr Child Health. 2007;43(7-8):532-8.
Mayo Clinic (2022). Iron deficiency anaemia (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. http://www.mayoclinic.org/diseases-conditions/iron-deficiency-anemia/home/ovc-20266507 [Accessed: 07/12/22]
Ngan, V. (2016). Iron Deficiency (Web Page). Hamilton: DermNet New Zealand Trust.
http://www.dermnetnz.org/topics/iron-deficiency/ [Accessed: 07/12/22] New Zealand Nutrition Foundation (2022). Iron (Web Page). Auckland: NZ Nutrition Foundation. www.nutritionfoundation.org.nz/nutrition-facts/minerals/iron [Accessed: 02/12/22]
University of Otago and Ministry of Health (2011). A Focus on Nutrition: Key findings of the 2008/09 New Zealand Adult Nutrition Survey. Wellington: New Zealand Ministry of Health. 2011. Available from: https://www.health.govt.nz/publication/focus-nutrition-key-findings-2008-09-nz-adult-nutrition-survey. Last Reviewed: September 2023
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