Essentiality and Safety of Trace Essential Chemicals : Time for a change of the RDA and RfD concept?

Abstract

In an attempt to promote scientific argument and to attain a consensus on the dietary requirement (RDA) and oral reference doses (RfD) of trace elements, this lecture discusses both the present status of RDA and RfD in Japan and other countries and the background of the need to determine such values, including the methods of determination and their associated problems with an emphasis on how to overcome the confusion observed between essentiality and safety of these elements and other trace chemicals, including dioxins.

As a conclusion, the followings are recommended ; 1. The concept and determination of RDA and RID should be based on both updated scientific evidence and human hazard assessment rather than animal risk assessment. 2. The concept of chronic disease or ageing prevention should be included in the development of future RDA. 3. Greater coordination is need between policy makers in both nutrition and toxicology to avoid unnecessary confusion. 4. The process of translating scientific findings into public policy is urgently needed.