Implementing food-based dietary guidelines for - United Nations ...

Nutrient risk assessment: Setting upper levels and an
opportunity for harmonization
Peter J. Aggett
Abstract
Upper levels are estimates of the quantity of a nutrient
that can be ingested daily over a lifetime without appreciable
risk to health. The approach to establishing upper
levels for nutrients, nutrient risk assessment, has derived
from the risk assessment of foreign chemicals that are
deliberately added to foods, or are in food as contaminants.
This process of risk assessment is rigorous and
transparent, particularly in dealing with the uncertainty
arising from the data available and their assessment and
extrapolation to human populations. Hazard identification
and characterization, i.e., a dose–response pattern,
as applied to xenobiotics, are discussed first, and then
the difficulties of applying this approach to nutrients are
reviewed. Nutrients, in contrast to foreign chemicals,
have specific and selective metabolic pathways and homeostasis,
as well as specific functions. This is the source
of differences in the nutrient risk assessments produced
by various national and international advisory bodies.
Although the same data are used in such exercises, different
judgments are made about identifying adverse
effects, the nature of uncertainties in the assessment, and
in matching the upper levels with exposure assessments
and dietary reference values. The establishment of different
upper levels for different national and international
communities is a source of confusion in public health
policy and practice and a barrier to trade. It is proposed
that a basis for harmonizing the existing approaches
used in nutrient risk assessment would be the collaborative
development of the model for establishing upper
levels of intake for nutrients and related substances that
has been recently described by a Joint Task Force of the
World Health Organization and the Food and Agriculture
Organization.
The author is affiliated with the Lancashire School of
Health and Postgraduate Medicine, University of Central
Lancashire, Preston, UK.
Please direct queries to the author: Peter Aggett, Lancashire
School of Health and Postgraduate Medicine, University of
Central Lancashire, Preston, PR1 2HE UK; e-mail: pjaggett@
uclan.ac.uk.
Key words: Nutrient risk assessment, upper levels,
adverse health effects
Introduction
This contribution addresses the assessment of the risk
or safety of high intakes or exposure to nutrients and
related substances. I will call this nutritional risk assessment,
although, of course, risk and safety assessment,
and, perhaps, the approaches described in this paper,
could be as readily applied to setting safe lower levels
of intake.
For this overview, an upper level of intake (UL) is
“the maximum level of habitual intake from all sources
of a nutrient or related substance judged to be unlikely
to lead to adverse health effects in humans”[1]. This
definition, in turn, requires at least two more definitions,
setting aside that of defining a nutrient or related
substance.
First, an habitual intake is “the long-term average
daily intake of the nutrient or substance”; second, an
adverse health effect is “a change in morphology, physiology,
growth, development, reproduction or lifespan
of an organism, system, or (sub) population that results
in an impairment of functional capacity, an impairment
of capacity to compensate for additional stress, or an
increase in susceptibility to other influences” [1].
A hazard is the inherent property of a nutrient
or related substance to cause adverse health effects,
depending on the level of intake.
These definitions have been derived from the processes
and definitions that have been applied to the risk
analysis, risk assessment, and regulation of human
exposure to xenobiotics as additives to our food, or
as natural toxicants or environmental pollutants and
contaminants in the food chain.
Since risk assessment approaches to setting ULs for
nutrients have drawn on these more established processes
for nonessential chemicals, this overview will first
describe these processes, and then discuss how such an
approach can be applied to nutrient risk assessment.
Food and Nutrition Bulletin, vol. 28, no. 1 (supplement) © 2007, The United Nations University. S27