iron deficiency anaemia

Iron deficiency anaemia

Iron deficiency anaemia is a common health concern, particularly among females of child-bearing age. However, a person can be deficient in iron and not have anaemia. Conversely, not all anaemia cases are caused by iron deficiency. Iron deficiency is the most common nutrient deficiency (1).

What is iron?

Iron is a mineral present in multiple proteins in the human body, such as haemoglobin in red blood cells and myoglobin in muscles (1, 2, 3). Iron-containing proteins are key for oxygen transport, DNA synthesis, generation of energy by mitochondria (1, 3), enzymatic processes (1), immunity and cell signalling (3).

Iron metabolism

The equation below illustrates what happens with iron in our bodies daily.

Iron in body
3-5g (1), 2-4g (3)
= iron intake
1-2mg (1, 3)
+ iron recycling (e.g. breakdown of red blood cells) (4), iron stores iron losses
1-2mg (1, 3)

Iron is not only lost through menstruation but also via sweat, skin, intestines, urinary tract (1, 4) and airways (4).

Causes of iron deficiency anaemia

One of the main causes is inadequate iron intake, due to consumption of foods that are not rich in highly bioavailable iron (1, 3, 5).

Menstrual blood loss is also a major cause of iron deficiency (1, 5).

There are also increased iron requirements in infants, young children and pregnant women to satisfy growth demands (1, 3, 5).

Other causes include:

  • blood loss (e.g. from colon cancer or ulcers) (1, 5, 6)
  • frequent blood donation (1, 5)
  • iron malabsorption (e.g. due to Coeliac Disease or gastric bypass surgery) (1, 3, 5, 6)
  • rare genetic mutations, for which oral iron supplementation is ineffective (1, 3, 5)

In addition, the hormone hepcidin controls the iron availability to tissues (1, 3). Hepcidin is overexpressed when iron concentrations of iron in the liver and plasma are high, but also as a response to inflammation and physical activity. When this happens, hepcidin decreases plasma iron concentrations (1).

Signs and symptoms of iron deficiency anaemia

The most frequent symptoms are fatigue, difficult breathing (1, 6), headache, paleness (1). Other symptoms include heart palpitations (1, 6), alopecia (hair loss), restless legs syndrome, dry and rough skin, dry and damaged hair (1), and weakness (6).

Anaemia can decrease physical performance and work productivity (1, 3). It also increases the risk of mother and child mortality and can impair cognitive and physical development in children.

Treatment for iron deficiency

Doctors normally prescribe iron supplements for patients with diagnosed deficiency. Unfortunately, these can produce side effects such as stomach discomfort, nausea, diarrhoea, constipation and dark stools (1, 5). It is important to know that absorption of iron from supplements is decreased when taken with meals (1).

In practice, iron supplements are effective in increasing haemoglobin and iron stores. They also may improve exercise performance and fatigue in women (5).

Iron in foods

There are 2 types of iron in foods: haem and non-haem. Haem iron contains haemoglobin and is present exclusively in foods of animal origin. Conversely, non-haem iron is present in both plant- and animal-based foods. Haem iron is absorbed 15-35% better than non-haem iron. (1, 4, 6)

Animal foods with the highest content of iron are, in descending order: liver, beef, lamb, pork and pork products, chicken, and fish (2).

The haem iron content in animal foods is highly variable, e.g. 48% in beef mince, 60% in roast/grilled lamb, grilled pork and chicken, 65% in roast/braised beef, 70% in rump steak. Haem iron is lost when cooking (30-35% when roasting/stewing, 10% when grilling/frying). Taking into account usual intake, losses, etc., it is estimated that the haem iron intake in Australia is 60% of total iron intake (2).

The graph below shows the amount of total iron in selected foods (7). Note that this graph does not differentiate haem vs non-haem iron, and that, as mentioned before, they have different rates of absorption.

What affects iron absorption?

Certain plant components such as phytates (in legumes, nuts, wholegrains, etc.) and polyphenols (in tea, coffee, cocoa, red wine, etc.) decrease iron absorption (1, 4, 6). Food preparation methods such as soaking, sprouting and fermenting can partially neutralise phytates (4, 6).

Calcium and non-meat animal proteins (e.g. from dairy or eggs) also inhibit iron absorption (1, 4, 6).

On the other hand vitamin C and intake of meat increase iron absorption (1, 4, 6).

In addition, people who are iron deficient absorb non-haem iron better (4, 6).

The estimated amount of dietary iron that is available to the body is approximately 18% for omnivores and 10% for vegetarians (6).

Recommendations

  • Don’t assume that you have iron deficiency just because you have some symptoms that might suggest it. Ask your doctor to check your iron levels and act accordingly. Iron overload is also a health concern.
  • If you are a woman with heavy periods, or eat a vegan or vegetarian diet or have a condition that affects nutrient absorption (such as Coealic Disease), ask your doctor to check your iron levels.
  • Haemoglobin levels alone are not sufficient for detecting iron deficiency. Your doctor should know how to order an interpret a full iron panel.
  • If you have been diagnosed with iron deficiency, look at increasing iron intake and maximising absorption first before taking supplements, as these can cause undesired side effects. Refer to the previous section.
  • Ask your doctor to re-test periodically to see if the deficiency has been corrected through diet or supplementation.
  • Just because a food is high in iron, it doesn’t mean it’s healthy.

References

  1. Lopez A, Cacoub P, Macdougall IC, Peyrin-Biroulet L. Iron deficiency anaemia. Lancet (London, England). 2016;387(10021):907-16.
  2. Rangan A, W. L. Ho R, Donald Blight G, Binns C. Haem iron content of Australian meats and fish1997. 508-11 p.
  3. Dev S, Babitt JL. Overview of iron metabolism in health and disease: Iron metabolism in health and disease. Hemodialysis International. 2017;21:S6-S20.
  4. Egli I, Hurrell R. Iron bioavailability and dietary reference values. The American Journal of Clinical Nutrition. 2010;91(5):1461S-7S.
  5. Low MS, Speedy J, Styles CE, De-Regil LM, Pasricha SR. Daily iron supplementation for improving anaemia, iron status and health in menstruating women. The Cochrane database of systematic reviews. 2016;4.
  6. Saunders AV, Craig WJ, Baines SK, Posen JS. Iron and vegetarian diets. Med J Aust. 2013;199(4 Suppl):S11-6.
  7. Food Standards Australia New Zealand (2014). AUSNUT 2011–13 – Australian Food Composition Database. Canberra: FSANZ. Available at www.foodstandards.gov.au

Leave a Reply