Iron deficiency in female runners is very common. In a 2000 study, 26 per cent of 126 female endurance athletes were iron deficient. For runners – and female runners in particular – iron is a key dietary component. It’s essential for the transportation of oxygen to aerobically-exercising muscles. It’s a very important element of haemoglobin, the oxygen-carrying protein in red blood cells, and is also an essential constituent in myoglobin, which transports oxygen within the muscle cells to the mitochondria (the powerhouse of the muscle cell). Within cells, iron is also an important component in the enzymes and proteins involved in the breakdown of glycogen and other fuel sources to produce energy.
Female runners are at particular risk of depleting their iron stores, as their requirements are higher. Blood lost through menstruation needs to be replaced and iron is required for new red blood cell production. Endurance exercise by itself stimulates red blood cell production and so iron requirements go up. Low dietary iron intake is a common cause so vegetarians and those who eat little red meat are particularly at risk. Iron is contained in red meat and turkey meat, and in green leafy vegetables, lentils and chickpeas. Other common causes of deficiency in runners include celiac disease, caecal slap syndrome (the walls of the gut slap together while you’re running, causing small amounts of blood loss), foot-strike haemolysis (red blood cells travelling through vessels on the soles of the foot get squashed with each foot strike) and inappropriate anti-inflammatory use (this can cause a small amount of bleeding from the stomach).
The main symptoms of a deficiency in a runner are fatigue and poor or reduced performance. You may notice your training times are slightly slower than you would expect. If the iron deficiency is not treated it can progress to frank anaemia (low haemoglobin concentration and red blood cell count). Anaemia causes symptoms of significant fatigue, lethargy and excessive shortness of breath on exertion.
It’s a good idea for all runners who notice fatigue or reduced performance to see their GP for a blood test to check their full blood count and ferritin level (iron stores). This will confirm whether there is any iron deficiency and whether or not there is any evidence of anaemia. A ferritin level lower than 30 mcg/L can cause impaired performance. You should aim to keep your ferritin level above 50mcg/L. For serious runners, a screening blood test to check the ferritin level can be very useful in identifying iron deficiency early and treating it before it becomes a problem. Ideally, have your ferritin level checked every six months, though this may not always be possible for GPs to do, owing to cost.
Iron deficiency can be treated by a high-dose oral supplement. The most commonly prescribed supplement is ferrous sulphate 200mg, which can be taken up to three times daily. Side effects include constipation and nausea and, if this happens, the dosage will be reduced to once or twice daily or an alternative iron supplement used. Typically, a runner with iron deficiency without anaemia (with no other cause for fatigue) should start to feel better within two or three weeks of taking iron supplements, but this depends on how low the iron levels are and how well you absorb iron. Taking vitamin C with the iron supplement helps absorption, and some supplements, such as Ferrograd C, have vitamin C in the same tablet. Avoid slow-release iron preparations, as your body absorbs iron from the first part of the gut. Caffeine, dairy products and calcium supplements can inhibit iron absorption, so supplements should be taken one or two hours either side of these. Iron absorption may be reduced immediately after a run, so time your supplementation or dietary intake away from training sessions.
The best way to prevent iron deficiency is to have adequate red meat in your diet (twice weekly will do the trick). Ideally, have your ferritin level checked every four to six months and, if it is between 30 and 50, then take ferrous sulphate 200mg on alternate days. If it is lower than 30mcg/L you will need a higher dosage in the short term (six to eight weeks) but be careful not to take too much iron, as this can lead to haemochromatosis, with symptoms including fatigue, joint pain and absent periods. If iron supplements are not increasing iron stores there may be an issue with malabsorption, which can be discussed with your doctor. Very occasionally an iron injection is required to treat low iron stores but a specialist in a hospital setting usually does this.
You should feel normal again, with no fatigue and be able to hit the training and racing times that you and your coach would expect.