Anaemia- iron deficiency in runners (part 2)

Anaemia- iron deficiency in runners (part 2)

This article looks specifically at the differences between a nominal iron deficiency '(sports anaemia' or 'athletic pseudoanemia') and full-blown anaemia.

Should an athlete's red blood cells not contain enough iron then the Sunday training session or race may be extremely hard work. Ranging from a hardly noticeable pre-latent iron deficiency, through to an overt iron deficiency anaemia - a poor iron profile will have definite implications for every endurance athlete, whatever their sport.

Anaemia part 1 explains:


The origin and function of red blood cells and expected normal ranges for a range of haematological indices.
The role of iron stores (ferritin) in the production of immature red blood cells (reticulocytes).
The vital roles of the iron containing compounds, haemoglobin and myoglobin in oxygen supply to working muscles and implications for performance.
Reasons for accelerated red blood cell turnover in athletes detailed and the implications for iron status reviewed.


Should an athlete's red blood cells not contain enough iron then the Sunday training session or race may be extremely hard work

To recap briefly,

Iron demand in athletes  

The red blood cells are subject to oxidative flux, osmotic shifts and also, through the impact of foot-strike when the cells pass through the exposed capillaries of the soles of the feet, a process known as foot-strike haemolysis. These stresses accelerate the ageing process of the cells (senescence). The cells are destroyed and haemoglobin is liberated into circulation. Occasionally this haemoglobin may not be re-gathered and it will be excreted. Small amounts of iron have been shown to be lost through sweating and also through small gastro-intestinal bleeds in conjunction with menstruation in females the above factors elicit a high demand for iron.

Iron deficiency vs. anaemia  

If iron deficiency is unchecked it will gradually develop into a full anaemia, whereby the haemoglobin count will fall to a subnormal level. Following a period of consistent iron store depletion, eventually the haemoglobin count will begin to fall. Bear in mind the correlations between haemoglobin concentrations and performance. Once an athlete's haemoglobin count falls lower than the levels shown below, they are said to be anaemic.

Males < 14g/dl (below fourteen grams per decilitre).
Females < 12g/dl

The likely incidence of a true anaemia is really quite low. The problem stems for an increased iron demand that is not balanced by an increased iron intake. Healthy athletes, discounting an underlying clinical disorder or recent blood loss, will more than likely demonstrate a normal, but accelerated, iron metabolism.

An athlete suffering from iron deficiency anaemia will feel fatigued, lethargic and may struggle to complete training sessions that previously would have been easily completed. Iron deficiency can be identified from a blood test.

If iron deficiency is unchecked it will gradually develop into a full anaemia

Does a low haemoglobin count definitively mean that an athlete has iron deficiency anaemia?

The phenomenon of highly trained elite athletes' blood profiles with lowered red cell count, haemoglobin and haematocrit has often been attributed to plasma shifts associated with high training volumes. This is often termed 'sports anaemia' or 'athletic pseudoanemia' and will not have an adverse effect on performance, as a true anaemia is not present. This explains why a range of other indices are examined within the blood including:

The mean cell volume of the cells (MCV)

Reference interval 80 - 96 fl
This parameter describes the average size of red blood cells. Younger red blood cells are much larger in size than the mature cells. Therefore conditions of increased red cell destruction and consequent increased rates of production are associated with increases in mean cell volume. The evidence to date is that elite athletes may have slightly higher mean cell volume than the sedentary population. It can be raised further in conditions of B12 or folate deficiency and it is decreased in iron deficiency anaemia.

Red cell mean haemoglobin content (MCH)  

Reference interval 27-32pg
This is the average amount of haemoglobin contained per blood cell. Low levels can indicate iron deficiency anaemia and other inherited disorders of haemoglobin synthesis - an example being thalessemia minor. Ii is influenced by plasma shifts.

Red cell haemoglobin concentration (MCHC)

Reference interval 32 - 36 g/dl
This is a mathematically calculated amount of haemoglobin relative to the cellular portion of the blood. This parameter is reduced in iron deficiency anaemia but it is also influenced by blood volume and plasma levels.

Percentage hypochromic red cells  

Reference interval up to 4%
This is the percentage of cells with a low haemoglobin content. The greater the number of cells with a cellular haemoglobin content less than 28g/dl. Should an athlete's iron stores be unable to supply the newly produced cells then the percentage of hypochromic cells will be increased.

Ferritin  

Reference interval
Males 30 -300 ng/ml
Females 10 -160 ng/ml

A diminished ferritin count generally reflects that iron stores are being compromised. However ferritin values can be quite unstable and care must be exercised when interpreting values in athletic populations. Ferritin counts may be increased during response to infections or inflammation.

Stages of iron deficiency  

Stage one - Pre-latent iron deficiency
  • Normal haemoglobin count
  • Blood count normal
  • Serum ferritin low
  • Decreased cellular haemoglobin content in reticulocytes (CHr)
Stage Two - Latent iron deficiency
  • Normal haemoglobin count
  • Serum ferritin low
  • Other iron indicators abnormal
  • Increased production of both hypochromic reticulocytes and mature cells
Stage Three - Overt iron deficiency anaemia
  • Low haemoglobin count
  • Low serum ferritin
  • Other iron indicators abnormal
  • High percentages of hypochromic red cells in circulation
  • This shows why athletes are at risk from compromising their iron stores
How can you actually tell if you are developing an iron deficiency before it is too late?

iron supplementOnce aware that iron stores are depleted (following information provided by having a complete blood count by our physician) the process of returning iron stores will begin. The physician will usually prescribe oral iron supplementation with the aim of returning the ferritin value to the normal range. The topic of iron supplementation and nutritional status in athletes is covered in Anaemia part 3.

Iron deficient erythropoiesis is a gradual process that passes through different stages before an overt anaemia develops. As mentioned above, this situation will have been developing over a long period of time and will have been evident in the erythrocyte precursors (immature red blood cells) known as reticulocytes. By the same token the recovery from the situation will also be equally visible.

The efficacy of any prescribed oral iron supplementation can be monitored by examining the cellular haemoglobin concentration of the reticulocytes (young red cells). This is a highly sensitive marker of a developing iron deficiency and it can also be used to track the expected increase in cellular haemoglobin content. This parameter is the most rapid response index to the newly available iron supplies.

Conclusion
  • Athletes are urged to have a blood profile done when they are performing well.
  • Poor performance may be due to a developing, or true, iron deficiency.
  • Where possible, request that a reticulocyte count be performed in addition to a full blood count and other markers of iron status.
  • This parameter will provide early indicators of a developing problem and subsequently give an idea of the rate of recovery from it.

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