How much iron is too much? New research investigate tolerable intake levels

A new article by the European Food Safety Authority (EFSA) Panel on Nutrition, Novel Foods and Food Allergens (NDA) has recently investigated the tolerable upper intake level (UL) for iron. Commissioned by the European Commission, the researchers conducted systematic reviews to analyze the effects of high iron intake. These reviews focused on three main areas: chronic disease risk, adverse gastrointestinal effects, and potential negative impacts of iron supplementation in infants, young children, and pregnant women.  

While the scientific community recognizes that systemic iron overload can cause organ toxicity, setting a UL for iron proved challenging. In 2004, the EFSA Panel attempted to establish the UL, but due to insufficient data, lacked to do so. The current assessment revisited these findings using advanced methodologies and more comprehensive dataset to arrive at a more robust conclusion. The derived safe intake levels from the EFSA Panel further benefit from comparisons with the findings of other respected risk assessment bodies, including the Institute of Medicine (IOM) and the UK Food Standards Agency's Expert Group on Vitamins and Minerals (EVM). This cross-referencing with established organizations adds an extra layer of context and validation to the UL proposed by the EFSA Panel.

Researchers observed the occurrence of black stools, indicating the presence of large amounts of unabsorbed iron in the gastrointestinal tract. While not adverse in themselves, black stools serve as a conservative marker in the sequence of events that could lead to systemic iron overload. Studies showed that black stools did not occur with supplemental iron intakes of 20-25 mg/day, alongside a background intake of 15 mg/day. Based on this, a safe intake level of 40 mg/day for adults, including pregnant and lactating women, was proposed.  

To determine safe UL for children and adolescents, the panel used allometric scaling based on body weight, accounting for growth-related physiological differences; Infants (7-11 months) 5 mg/day, Children (1-3 years) 10 mg/day, Children (4-6 years) 15 mg/day, Children (7-10 years) 20 mg/day, Adolescents (11-14 years) 30 mg/day, Adolescents (15-17 years) 35 mg/day, Infants (4-6 months) 5 mg/day excluding infant and follow-on formulae.  

The EFSA Panel concluded that a total daily intake of 40 mg of iron is unlikely to cause adverse effects, even for pregnant and lactating women. This conclusion is based on conservative evidence and aims to prevent systemic iron overload, a serious condition where iron accumulates in the body to toxic levels. However, this recommendation differs slightly from a traditional tolerable UL, which defines a specific threshold where adverse effects are more likely. Instead, this recommendation is based on conservative evidence, erring on the side of caution without pinpointing an exact tipping point. This comprehensive assessment highlights the critical importance of monitoring iron intake from all dietary sources, including fortified foods and food supplements particularly for vulnerable populations like infants and pregnant women, who have different iron needs and require closer attention to potential health risks.    

Source:  

EFSA Journal