Iron is an essential trace element that has important metabolic functions, including oxygen transport and storage and many redox reactions. Insufficient intake results in the deficiency condition anaemia, adverse outcomes of pregnancy, impaired psychomotor development and cognitive performance and reduced immune function.
Case reports of accidental poisoning with medicinal iron, especially in young children, indicate acute damage of gastrointestinal, hepatic, pancreatic and cardiovascular structures after ingestion of very high doses. An acute oral dose of 60 mg iron/kg body weight can be lethal but oral doses below about 10-20 mg iron/kg body weight do not cause acute systemic toxicity.
Adverse gastrointestinal effects (e.g. nausea, epigastric discomfort, constipation) have been reported after short-term oral dosage at 50-60 mg daily of supplemental non-haem iron preparations, particularly if taken without food.
Iron overload with clinical symptoms, including liver cirrhosis, has been reported in individuals receiving long-term, high-dose medical treatment with iron (160-1200 mg iron/day). Iron overload with clinical symptoms has also been found in subjects homozygous for hereditary haemochromatosis (a genetic disorder of iron storage), even at normal dietary iron intakes. Bantu siderosis, with liver cirrhosis and diabetes, has been attributed to chronic excess intake of highly available iron (50-100 mg iron/day) in beer; however, these adverse effects may be confounded by chronic alcohol intake and possibly by a genetic disorder.
Although a proportion of the population has serum ferritin levels indicative of elevated iron stores (above 200 ?g/L for women and 300 ?g/L for men), the point at which an elevated serum ferritin level becomes associated with an increased risk of adverse effects (such as liver fibrosis) is not known. The risk of adverse effects from iron overload in the general population, including those heterozygous for hereditary haemochromatosis, is considered to be low.
Epidemiological studies have reported associations between high iron intake and/or stores with increased risk of chronic diseases such as cardiovascular disease, type II diabetes and cancer of the gastrointestinal tract. However, these data are conflicting and do not provide convincing evidence of a causal relationship between iron intake or stores and such chronic diseases.
The Panel considered that the available data are insufficient to establish a tolerable upper intake level for iron.
Based on estimates of current iron intakes in European countries, the risk of adverse effects from high iron intake from food sources, including fortified foods in some countries, but excluding supplements, is considered to be low for the population as a whole, except for those homozygous for hereditary haemochromatosis (up to 0.5% of the population). However, intake of iron from food supplements in men and postmenopausal women may increase the proportion of the population likely to develop biochemical indicators of high iron stores. Some groups at special risk for poor iron status, such as menstruating women or children, could benefit from additional iron intake and/or improved availability of dietary iron.