Based on the most current scientific evidence, the European Food Safety Authority (EFSA) has set new safe daily intake levels for iron, in lieu of a tolerable upper intake level (UL), which could not be established. The newly determined safe intake levels can help inform risk managers involved in the production of iron supplements and iron-fortified food products.

Iron is an important nutrient, but excessive intake over time can lead to negative health impacts, especially on the liver. Additionally, high-dose iron supplements may also cause adverse effects in the gastrointestinal tract. Based on the available data, EFSA has set a safe level of total iron intake at:

  • 40 milligrams (mg) per day for adults, including pregnant and lactating women
  • 10–35 mg per day for children 1–17 years old, with intake increasing by age
  • 5 mg per day for infants aged 4–11 months, including iron intakes from fortified food and food supplements, excluding that from infant or follow-on formula.

When assessing the safety of nutrients, no risk of adverse effects is expected unless a threshold intake is exceeded. The identification of this threshold is used as a basis to establish a UL. In 2004, EFSA’s Panel on Nutrition, Novel Foods, and Food Allergens published a scientific opinion on the UL for iron, at which time the data were insufficient to establish a UL for iron.

In response to a request from the European Commission, EFSA reviewed the 2004 scientific opinion on iron. In the case that the data were insufficient to set a UL, the Commission asked EFSA to advise on the safe level of intake, which is the maximum amount that confidently poses no risk of adverse effects in the general population. As opposed to ULs, safe levels of intake are not based on an identified threshold of intake above which the risk of adverse intake starts to increase, and intake levels above the safe levels of intake do not necessarily mean that there is a risk of adverse effects. Additionally, safe intake levels cannot be used to characterize the proportion of the population at risk of adverse effects.

EFSA commissioned the University of Copenhagen, the University of Oslo, and the Karolinska Institutet to carry out a literature review, which the agency used to assessed the potential negative impact on health related to high iron intake. The information collected was insufficient to define a UL, mainly because toxicity data were mostly in the form of individual case reports. Regardless, toxicity in the case reports was observed to be solely a result of iron overload from excess iron intake. Therefore, liver toxicity was observed even in people without underlying diseases that affect iron absorption, and is generally present in patients with liver failure and liver cancer.

The new UL was based on the occurrence of black stool, which in itself does not indicate harm to human health, but points to high unabsorbed iron levels in the gastrointestinal tract.