The oxidative stress and the in vivo consequences caused by free iron (reactive iron species) have been studied in detail. Many of the deleterious effects of hemochromatosis and other chronic iron overload conditions can be attributed to free iron. Some cancers, aging, neurodegenerative diseases and atherosclerosis can also be contributed to reactive iron species. The effects of iron excess can be generalized and chronic intake of supplements containing high amounts of iron can be a cause of iron overload.
In a recent study, iron-normal and iron-deficient rats were subjected to twice daily iron supplementation for 24 days providing a total daily dose 10 times their normal food iron intake(comparable to 120mg/d doses in humans). Initially the rats absorbed 10% and 21% of supplemental iron respectively. By day 7 of supplementation, in both groups of rats, absorption declined to 6%. When the rats were killed on day 24, it was found that levels were elevated above the levels absorbed in normal unsupplemented rats. In duodenal mucosa, iron levels were elevated 5-6 times; in ileac mucosa 2-4 times and an elevation of 3-4 times in the liver. Liver iron was slightly above normal as seen on supplementation day 3, after which the previously iron-deficient rats always showed higher liver iron levels that continued to increase beyond normal levels. These results support the fact that a fraction of supplemental iron is continuously absorbed beyond normal rates resulting in excessive liver iron levels, particularly in the previous deficient animals. This raises the question of whether iron-deficient pregnant women are moresusceptible to oxidative stress resulting from excessive iron absorption, particularly when givendaily pharmacological doses of iron.
It has been found that both generalized iron excess as well as deficiency, are situations where free radical damage has been observed and can lead to functional disturbances and genetic alterations.However, excessive oral iron supplementation during pregnancy cannot produce permanent whole body iron overload unless the person receiving the supplements has genetic alteration inthe regulation of iron absorption and metabolism. Chronic ingestion of bio-available daily doses in clear excess of the upper tolerable intake level (45mg) can induce iron overload, although this condition is rare. However, temporary iron overload could be produced if passive diffusion of soluble iron molecules are transported to the liver.
A study was carried out to assess the effect on the outcome of pregnancy of iron overdose. 51 patients were included in the study. Two were reported not pregnant and 49 were reported as pregnant patients, all took iron overdoses. Of the 49 pregnancies, 43 resulted in live babies, two had spontaneous abortions and four had elective terminations. Of the live babies, three were premature, and three other babies were born with abnormalities.
Balanced iron nutrition and hematological status are clearly critical throughout pregnancy for both the mother and fetus.
Resources:
1. Casaneuva E, Viteri FE. Nutrition as a Preventive Strategy Against Adverse Pregnancy Outcomes. Iron and Oxidative stress. J Nutr. 2003;133:1700.
2. Sungthang R, Mo-Suwan L, Changsuvivatwong V, Geater AF. Once Weekly and %-days a Week Iron Supplementation Differentially Affecting Cognitive Function but Not School Performance in Thai Children. J Nutr. 2004;134:2349-2354.
3. Fellman V, Rapola J, Pihko H, Varilo T, Raivio K. Iron Overload Disease in Infants Involving Fetal Growth retardation, Lactic Acidosis, Liver Haemosiderosis and Aminoaciduria. Lancet, 1998;351:490-493.
4. McElhatton PR, Roberts JC, Sullivan FM. The Consequences of Iron Overdose and Its Treatment with Desferrioxamine in Pregnancy. Hum Exp Toxicol. 1991;10:251-9.
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