Minimising the population risk of micronutrient deficiency and over-consumption: A new approach using selenium as an example

Background: At the present time the recommended daily intake or allowance (RDA) and the safe upper level (UL) of intake of micronutrients are given as single values. The recommended daily intake is considered to cover the requirements of 97.5% of the population while the safe upper level is a value for the whole population. These values provide only limited guidance to risk managers. 

Aim of the study and methods: A method has been developed recently which models the relationships between intake and risks of either deficiency or excess using an observed incidence for each effect and population distribution characteristics. Using this model it is possible to formulate advice to risk managers on the incidence (prevalence) of adverse effects, due to either deficiency or excess, at different levels of intake. 

Results and conclusions: Application of the model to the data used to derive the RDA and UL for selenium shows that it can predict the impact of changes in nutrient intake on the balance between benefit (absence of deficiency) and risk (development of toxicity). Application of the model has illustrated the utility of this approach, but highlighted the need for a comprehensive evaluation of the data and a critical appraisal of the validity of the relationships that are analyzed. In addition, the derived incidences will usually relate to effects with different biological or health impacts, so that the final balance between benefit and risk should be developed by a dialogue between the risk assessor and the risk manager.