Assessment of Copper Intake in Relation to Tolerable Upper Intake Levels

ABSTRACT

The Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen for mattrygghet, VKM) has, at the request of the Norwegian Food Safety Authority (Mattilsynet; NFSA), evaluated the intake of copper in the Norwegian population in relation to tolerable upper intake levels (ULs). VKM has also conducted scenario calculations to illustrate the consequences of amending maximum limits for copper to 1, 2, or 3, mg/day in food supplements. The existing maximum limit is 4 mg/day. Copper is a micronutrient essential for energy utilisation, brain function (neurotransmitter regulation), soft tissue and bone (collagen synthesis), nutrient metabolism (especially iron) and antioxidant defence against free radicals. Foods account for 90% or more of copper intake in adults when the copper content in drinking water is low (< 0.1 mg/L). If the copper content is higher (> 1-2 mg/L), water may account for up to 50% of total intake (EFSA, 2015). We reviewed four risk assessments undertaken by the Institute of Medicine (IOM), Scientific Committee on Food (SCF), Expert Committee on Vitamins and Minerals (EVM), and the Nordic Nutrition Recommendations (NNR). Liver damage was selected as a critical endpoint from which to derive a UL because it was judged to be the most reliable marker and consequence of a long-term chronic high copper intake. However, copper-related liver damage is observed almost exclusively in patients with genetic predispositions of copper accumulation. VKM suggest to use the UL at 5 mg/day (NNR Project Group, 2012; SCF, 2003). This UL was derived from human studies.In the light of the evidence, SCF decided that an uncertainty factor (UF) of 2 was adequate to allow for potential variability within the normal population, whereas the Institute of Medicine (IOM) applied a UF of 1. VKM find the higher UF suitable because human data is limited, the uncertainty of the copper content of drinking water and the potential severe and irreversible adverse effects. According to the scenario calculations, adults and 13-year-olds with high copper intakes from regular foods (95 th percentile) will exceed the ULs with supplemental copper at doses of 3 mg/day or higher. 9-year-old children will exceed the UL with use of 2 mg supplemental copper per day. For younger children the ULs will be exceeded in more than 5% without adding supplemental copper. In our calculations, copper from drinking water is not included. Copper concentrations in annual samples from waterworks are in general below 0.1 mg/L (Nordheim et al., 2016).