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Ann Nutr Metab 2001;45(3):91-101 |
Safety aspects of iron in food.
Schumann K.
Walther-Straub-Institut fur Pharmakologie und Toxikologie, Ludwig-Maximilians-Universitat
Munchen, Deutschland. k.schuemann@lrz.uni-muenchen.de
During the last decades efforts regarding dietary iron supply focused mostly on
the prevention of deficiencies, especially during growth and pregnancy.
Correspondingly, homeostatic mechanisms increase intestinal iron absorption in
iron deficiency, but its downregulation at high intake levels seems insufficient
to prevent accumulation of high iron stores at high intake. There is no
regulated iron excretion in overload. Excess of pharmaceutical iron may cause
toxicity and therapeutic doses may cause gastrointestinal side effects. Chronic
iron excess, e.g. in primary and secondary hemochromatosis, may lead to hepatic
fibrosis, diabetes mellitus and cardiac failure. Chronic intake of 50-100 mg
Fe/day of highly bioavailable iron with home-brewed beer in sub-Saharan Africans
lead to cirrhosis and diabetes. Applying a safety factor of 2 would lead to an
upper safe level of 25-50 mg Fe/day for this endpoint of conventional iron
toxicity. However, beyond this kind of damage iron is known to catalyze the
generation of hydroxyl radicals from superoxide anions and to increase oxidative
stress which, in turn, increases free iron concentration. This self-amplifying
process may cause damage to lipid membranes and proteins, which relates radical
generation and organ damage after ischemia-reperfusion events to available free
iron in clinical and experimental settings. Correspondingly, epidemiological
studies as well as observations in heterozygotes for hereditary hemochromatosis
suggest that the risk of atherosclerosis and acute myocardial infarction is
related to body iron stores, though there is conflicting epidemiological
evidence as well. The most recent and best controlled studies, however, support
the hypothesis that iron stores are related to cardiovascular risk.
Iron-amplified oxidative stress may also increase DNA damage, oxidative
activation of precancerogens and support tumor cell growth. This is supported by
experimental, clinical and epidemiological observations. Due to these mechanisms
high iron stores may present a health hazard. Though this has not been finally
proven, available evidence strongly recommends not toincrease iron intake beyond
physiological requirements. To avoid iron deficiency symptoms, on the other
hand, care must be taken to meet recommended daily intake. Copyright 2001 S.
Karger AG, Basel
Publication Types:
· Review
· Review, tutorial
