Written by Christopher Tack
Iron Intake & The Female Athlete
What do Angelina Jolie, Selena Gomez, Venus Williams and the late singer and drummer Karen Carpenter have in common?
The answer is that they have all suffered the impact of iron deficiency and anaemia. In the case of Venus Williams, whilst hers was a part of a larger auto-immune condition (Sjögren’s syndrome), the impact on her as an elite sports person is distinctly relevant to this article in which we will examine the influence of iron deficiency on female athletes and the potential benefits of iron supplementation. If anaemia did not prevent Venus amassing 7 grand slam tennis titles, then hopefully you will not be inhibited in your pursuit of fitness and sports performance.
What Is Iron & Why Is It Important?
Iron deficiency is likely the most common nutrient deficiency in the western world (1). Iron deficiency anaemia is a condition where a reduction in iron leads to a reduction of red blood cells, and this condition is seen to have a higher prevalence in athletic groups, particularly females (2). The presence of this deficiency has a direct impact on athletic performance in the affected population.
Iron is an important mineral which is used in a variety of our body’s functions. Specifically, iron is required to make new red blood cells and is a component of the haemoglobin in our red blood cells which carries oxygen around the body. Obviously, our tissues (such as brain tissue or muscle) will have a vital requirement of oxygen, and when the amount of oxygen supplied by the blood is diminished, a variety of symptoms can be apparent.
Symptoms of iron deficiency vary but include tiredness (lack of energy) and cardiorespiratory sensations such as shortness of breath and heart palpitations (particularly on exertion). Other symptoms can include headaches, tinnitus, altered taste and hair loss- just to name a few!
What Causes Iron Deficiency?
A reduction in iron is caused by a number of different mechanisms which include iron loss through increased perspiration, plasma expansion during activity, blood loss and malnutrition (1). Additionally, the bodies levels of iron can be diluted in a process called dilutional pseudo anaemia where exercise cause fluid retention.
Iron deficiency has two phases. The first is the depletion phase where the levels of the protein ferritin in the blood reduce to below 12ng/ml (indicating significant reductions in iron). The second phase is where this iron loss transfers to cause abnormal levels of blood haemoglobin, indicated by altered haematocrit readings on blood testing.
You may ask, why this occurs in otherwise healthy athletes. The truth is that the intensity of exercise training and performance can quickly deplete iron stores, leaving athletes at risk of anaemia. Dietary recommendations for iron tend to be increased by 1-2 x the normal requirement, with vegetarians being on the upper limit of this recommendation. Reduced ferritin levels indicative of phase I deficiency are widely reported in endurance athletes (3-7), and this degree of iron loss is more prevalent in females (8-10). Obviously, during intense exercise, the demand for oxygen (and as such iron) is greater. In fact, exercise will increase the number of red blood cells circulating in the blood stream, and this needs to be matched by iron intake. Additionally, if activities lead to blood loss (e.g. contact or combat sports participants) this would mean a higher requirement for iron replacement.
The risk of iron deficiency is obviously also greater in female athletes due to the blood losses during menstruation (1). During the menstruation process, 0.5mg of iron is lost per day, and a loss of 60ml of blood per day are particularly susceptible to iron deficiency. On the other side of this coin are females who are amenorrhoeic, as although they do not suffer the same blood loss, it is likely that their total dietary intake of iron is unsatisfactory.
Impact Of Anaemia?
The reason for worrying about iron deficiency is that iron status is associated with physical performance. In essence, if you are performing with an iron deficiency it is likely that your performance will be hindered.
A study from 2012 (11) examined a group of 48 female competitive rowers, half of which had an iron deficiency (but DID NOT have anaemia). The athletes completed a questionnaire about their diet, physical activity and menstrual status. They were then asked to complete a 4km row at 85% of their VO2max. Blood and respiratory gases were collected throughout the test.
The findings of this study reported that rowers with iron deficiency (phase 1) consumed the same calories and iron intake as those who were not deficient. The deficient group also had 2km personal records which were 18 seconds slower than the non-deficient group, and iron deficiency was associated with a lower VO2max. In the 4km time trial, this meant a 2.8% slower time.
The reasons behind this are likely attenuated by training, as the deficient group also reported that their training schedule was on average 11 minutes shorter than the healthy group, which may explain the lower VO2max readings and slower performance.
Benefits Of Iron Supplementation
It is clear that deficiency in iron stores can cause us to perform both in training and competition sub-optimally. Therefore, it is worth asking what benefit can be made with the provision of iron supplements or an iron-rich diet to a deficient athlete?
A group of researchers published a paper in the Medicine and Science in Sports and Exercise journal which examined this question (12). A group of 18 phase I deficient female endurance runners were recruited, their VO2max and total time to exhaustion were obtained. These subjects were then divided into a supplement group and a control group. The supplement group consumed 160mg of ferrous sulphate equivalent to 50mg of elemental iron twice daily for a period of 8 weeks. The findings showed that supplementation not only raised the serum levels of ferritin but also increased total time to exhaustion by 25.5%.
These benefits of iron supplementation in a deficient athletic population have been confirmed further in studies. Iron deficient endurance cyclists were given 100mg of ferrous sulphate per day over 6 weeks. Results found that they decreased their 15km race time (13). Alongside this, the athletes also improved their running times (14).
A further study (15) examined the impact of a 2 week period of iron therapy in female athletes. These athletes had phase I deficiency with only minimally decreased haemoglobin values. The first findings were that the provision of additional dietary iron raised both iron and haemoglobin levels up to that of the healthy control group. However, this amount of supplementation failed to improve performance on an exercise bike protocol where subjects were pushed to exhaustion.
Despite this finding, another benefit to iron supplementation was apparent. This was that blood lactate levels at maximal exercise capacity decreased in the deficient group by 18%, perhaps indicating that iron supplementation to normal levels can boost its function in oxidative metabolism and reduce lactate accumulation during exercise.
Take Home Message
If you are a female athlete who struggles with fatigue and difficulty sustaining endurance performance, then it may be worth getting a blood test to measure your levels of ferritin and haemoglobin. Even if you are only phase I deficient in iron, the evidence shows that this is sufficient to inhibit your activity and is easily benefited by supplementation with ferrous sulphate. A dose of 100mg per days is enough to boost your capacity to perform; however remember that performance is dependent upon your training.