Literature search and review related to specific preparatory work in the establishment of Dietary References Values for Copper (Lot 3)
The objective of this literature search and review was to identify the data from 1990 onwards upon which Dietary References Values (DRVs) for copper may be based. Articles were searched using three databases: Pubmed, Cochrane and Embase. Additional studies were identified by checking the reference lists of relevant reviews. Moreover, reports on DRVs from several countries were also considered as well as one study published in French relating to copper intakes in the French population. The search resulted in a total of 8004 references to screen on the basis of title and abstracts. 246 articles were then assessed from full text publications and 83 were finally included in this review. Because of the lack of specific health outcomes related to copper intake, a large array of diseases was thus considered for the review. Cardiac arrhythmia, cancer, arthritis, cognitive functions, respiratory disease and cardiovascular mortality were considered. No conclusion about the influence of copper intakes could be drawn from these studies. Studies identified also focused on copper status biomarkers as well as on copper metabolism and bioavailability, particularly its absorption and its excretion. Copper balance was sometimes calculated but only faecal and/or urinary copper losses were taken into account and these studies were therefore graded as at high risk of bias. Studies presenting only copper intakes in representative samples of national populations were included. Data concerning Cu intake of representative samples of healthy populations may indeed be useful to define an adequate intake for copper in case it would not be possible to estimate an average requirement due to lack of data, relevant criteria and/or good quality studies. Overall, the majority of studies were at high or moderate risk of bias and it seems that the evidence on which DRVs may be based for copper is poor.