Chemistry Reference
In-Depth Information
appropriate to recommend intakes of selenium that
resulted in maximum peroxidase activity, namely
55
6 CONCLUSIONS
g/day. The differences noted in the UL were
a result of applying an UF of 2 to the threshold for
selenosis by WHO (1996) and the IOM/FNB (2000),
whereas the SCF (2000c) thought an UF of 3 was more
appropriate.
As for iron, the bioavailability of dietary and sup-
plemental zinc must be considered in deriving an
AROI. The values in Table 3 are the intakes for adult
men consuming a diet in which zinc was moderately
available (defi ned by WHO [1996] as 30-35%). All
three groups used factorial modeling to determine
the minimal quantity of absorbed zinc required to
replace endogenous losses. The lower boundary of
the SRPMI was based on a CV of intakes of 25%, and
the IOM assumed a 10% CV in requirements to cal-
culate the RDA from the EAR of 9.4 mg zinc/day.
The upper boundary of the AROIs in Table 3 indi-
cate a marked difference between the ULs derived
by WHO and the IOM/FNB and that recommended
by the SCF. The three ULs for zinc are based on the
intake of zinc that affects relevant indicators of cop-
per status as the critical effect. In all studies evalu-
ated, humans were given extremely soluble (highly
bioavailable) zinc supplements while consuming
diets containing approximately 10 mg of zinc. The
IOM/FNB used a study in which 50 mg of supple-
mental zinc was provided to humans for 10 weeks.
Decreased activity of ESOD was noted at this total
intake of 60 mg zinc/day. A UF of 1.5 was considered
adequate to account for interindividual variability
in response and the fact that a LOAEL was used.
The SCF (2003b) evaluated four studies in humans
in which several relevant indicators of copper sta-
tus were measured after zinc supplementation. No
adverse effects were observed at total zinc intakes
between 40 and 53 mg/day for 90 days. An intake of
50 mg zinc/day was considered a NOAEL, and an
UF of 2 was applied because of the small number of
subjects in relatively short-term studies. The recom-
mended UL of 25 mg total zinc/day raises an impor-
tant point mentioned earlier, namely, recommending
intakes without full consideration of nutritional
needs, or as in this case, the fact that thousands of
humans worldwide have daily intakes of zinc well
above the recommended UL without any signs of
adverse health effects. It was mentioned (SCF, 2003b)
that the 97.5 percentile of total zinc intakes of all age
groups are close to the UL. However, it should be
noted that the 95th percentile intake of total zinc
of adult men in the United States is 30.5 mg/day,
pregnant women 39.7 mg/day, and lactating women
46.7 mg/day (IOM, 2001).
µ
From this review, we recommend the following:
1. A set of principles and methods for the assess-
ment of risks from essential metals.
2. The use of these principles and methods for the
development of AROIs for EMs and other nutrients be
expanded globally whenever such risk assessments
are carried out.
3. Nutritional and toxicological information should
be considered in a balanced approach on the basis of
adequate human data.
4. Speciation, bioavailability, and homeostatic
mechanisms should be taken into account.
5. Critical effects of defi ciency and toxicity should
have similar clinical signifi cance.
6. During the risk assessment process for EMs,
greater emphasis should be given to the risk
characterization step to increase the transparency of
the process and to provide guidance to those using the
evaluations of the strengths and weaknesses of each
step in the process.
7. An acceptable range of oral (individual) intakes
(AROI) and a safe range of population mean in-
takes (SRPMI) can be defi ned if adequate data are
available.
References
Alexander, J. (1993).
Scand. J. Work Environ. Health
19(1),
122-123.
Alexander, J., and Meltzer, H. (1995).
In
(A. Oskarsson, Ed.). Risk
Evaluation of Essential Trace Elements—Essential Versus
Toxic Levels of Intake. Vol. 18. Nordic Council of Ministers,
Copenhagen.
Baer, M., and King, J. (1984).
Am. J. Clin. Nutr.
39,
556-570.
Barnes, D. G., and Dourson, M. L. (1988).
Regul. Toxicol. Pharmacol
.
8,
471-486.
Borch-Iohnsen, B., and Petersson-Grawé, K. (1995).
In
(A. Oskarsson,
Ed.). Risk Evaluation of Essential Trace Elements—Essential Ver-
sus Toxic Levels of Intake. Vol 18. Nordic Council of Ministers,
Copenhagen.
Bradbear. R. A., Bain, C., Siskind, V.,
et al.
(1985).
J. Natl. Cancer Inst.
75,
81-85.
Chen, X., Yang, G., Chen, J.,
et al.
(1980).
Biol. Trace Element Res.
2,
91-107.
Cunningham, J., Fu, A., Mearkle, P.L.,
et al.
(1994).
Metabolism
43,
1558-1562.
FAO/WHO. (2006). “A Model for Establishing Upper Levels of Intake
for Nutrients and Related Substances: Report of a Joint FAO/WHO
Technical Workshop on Food Nutrient Risk Assessment.” WHO
Headquarters, May 2005. World Health Organization, Geneva.
Frey, H. (1995).
In
“Risk Evaluation of Essential Trace Elements—
Essential versus Toxic Levels of Intake.” (A. Oskarsson, Ed.) Vol
18. Nordic Council of Ministers, Copenhagen.
Hess, F., King, J., and Margen, S. (1977). .
J Nutr.
107,
1610-1620.
IOM (Institute of Medicine). (1998). “Dietary Reference Intakes:
A Risk Assessment Model for Establishing Upper Intake Levels
of Nutrients.” National Academy Press, Washington, DC.
