Estudio de la toxicidad producida por la suplementación continua de hierro. Pautas nutricionales en niños y jóvenes para una correcta optimización de la actividad física saludable

Abstract

Iron supplementation is common in many sportsmen and teenagers. Although the positive effects of a continuous iron supplementation for anaemic people or people with iron deficiency are well known, the negative effects of an unnecessary iron supplementation are still uncertain, even though in fact sportsmen have normal levels of iron. In order to asses the possible toxicity of different doses of iron (3 mg/kg weight and 6 mg/kg weight) a model with animal experimentation have been used. Thirty Charles River rats have been divided into 3 groups: control group, group of 3 mgFe/kg weight and group of 6 mgFe/kg weight. After 10 days of adaptation to the new life conditions, half of the animals of each group were fed with an iron supplement during 45 days and the other half was fed with the supplementation until 90 days. Once the animals were slaughtered following the protocol proposed by the Ethics Committee and Scientific Council of the Faculty of Sports Science of the University of Oporto and the National Institute of Health, the ultra-estructural disorders in various myocardial cells and cells from the soleus muscle were analysed. A biochemical study was done as well, consisting in the logging of the number of leukocytes and haematites besides different metabolic aspects of the animals: weight, water and food ingestion, etc., were registered. The statistical program Spss 17.0 for Windows was used for the data treatment. In the cytological test a transmission electron microscope Zeiss EM 10a to 60 Kvolts was used. The results show a decrease in the number of leukocytes in the groups fed with an iron supplement and a light increase in the number of haematites. Apart from this, a lower weight gain was registered in the rats that were iron supplemented, especially for the group of 6 mgFe/kg weight. The existence of oedemas, lipid inclusions and giant mitochondrias were detected through the microscopic analysis, being this damage greater in the myocardial cells than in the soleus muscle. Other sign of the existence of damage and oxidative stress was found by means of the analysis of the CS, GSH and GSSG, resulting in a decrease of the CS and GSH values in the groups with an iron supplement of 6 mgFe/kg and 90 days of duration comparing with the control group, and therefore an increase in the GSSG values, that indicates the presence of a high level of oxidative stress. Finally, although there is an increase in the number of haematites that initially could favour the oxygen transference and enhance the yield of the sportsman, there are many parameters that indicate that also a high level of oxidative stress and toxicity are produced by this supplementation, therefore cost might be greater than benefits. It might be in our best interest continue with this research area, since nowadays many trainers and sport technicians are suggesting iron supplementation to their sportsmen without a previous blood analysis.