Legumes and spinach are good sources of non-haem iron, However, the iron is better absorbed from red meat.
Iron losses through exercise are generally not considered to be of importance. However, examination of sweat from healthy subjects shows that iron losses through perspiration can be around 11.5 μg per litre in sedentary individuals (here) and may be considerably higher during intense exercise. Giving consideration to these losses is therefore worthy of attention, especially to those who may have marginal iron stores prior to a period of intense exercise. The understanding that the skin is a route of excretion for minerals is interesting because it explains some of the increased mineral requirements for those who undertake regular exercise. Coupled to the increased rate of metabolic flux, the exercising individual can increase requirements of vitamins and minerals above that which is possible to attain through food. This calls into question the wisdom of the ‘we get all the nutrients we require from food’ mantra that is regurgitated ad nauseum from the mainstream medical establishment.
When considering iron losses through exercise, most researchers have concentrated efforts on understanding metabolism is female subjects because of the increased likelihood of low iron status in such individuals. This is particularly true of female athletes who would be considered an at risk group for the development of anaemia. In elite athletes this is of considerable importance because iron losses through exercise can decrease performance significantly thorough reductions in work capacity, and even marginal deficiencies can result in poor athletic performance. Research that has assessed the ability of physical activity to affect iron status have reported detrimental changes to iron status through moderate exercise. For example, in one study1 researchers monitored previously untrained female subjects who underwent a 35 minute a day, 4 day per week aerobic style exercise regimen. While none of the subjects developed iron deficient anaemia, changes to iron stores did occur, suggesting that iron repartitioning had occurred as a result of exercise.
Haemoglobin decreased in the exercising subjects compared to the sedentary subject between weeks 6 and 13, after initially rising from weeks 0 to 6. This suggests that the initial improvements in haemoglobin through a training effect were curtailed by compromised iron stores. Data showing a reduction in ferritin and haematocrit levels from weeks 6 to 13, mirroring the decrease in haemoglobin, supports this viewpoint. By week 13, ferritin levels had dropped below baseline levels suggesting iron losses through exercise. The iron, ascorbic acid, protein and energy intakes of all individuals was similar. The changes to the iron status of the exercising groups, coupled to the comparable nutritional intakes of sedentary subjects supports the contention that exercise increases the requirement for minerals. Interestingly in this study, despite no change to energy intake as well as a considerable increase in physical activity, none of the subjects showed improvements in body composition, further disproving the exercise fallacy of weight loss.
Iron losses through exercise and the effects of supplemental iron in athletes have been investigated by other authors. In another study2, researchers supplemented 30 mg of iron to athletes who were iron deficient over a 6 week period. The supplemental iron increased the serum ferritin of the treatment group significantly. In addition, while the iron deficient group displayed a decline in their ventilatory threshold during the 6 week study, those receiving the iron supplement had a ventilatory threshold that did not change. When the authors analysed these two variables (serum ferritin and ventilatory threshold) they found that there was an association between the two. Further, the iron supplemented group also increased their gross energetic efficiency during a submaximal test and changes in serum ferritin were inversely associated with the respiratory exchange ratio during the test. Therefore iron losses through exercise can have a significant effect on performance and supplementation can correct the deleterious effects of poor iron status.
