Zinc and Health: Workshop Summary
Session VI, Zinc and Growth in Specific Disease Entities incorporated
several themes under one session. The importance of zinc and its
protection against oxidant stress was reviewed through work done in animal
models of zinc deficiency. In these models of increased susceptibility
to oxidant stress was measured by hepatic damage, due to particular hepatocellular
toxins, as well as due to increased oxidation of lipoproteins. Guided through
a series of elegant studies, which were designed to unravel the mechanism
for growth failure that is associated with zinc deficiency, it was demonstrated
that providing IGF resulted in no benefit in terms of a growth response
to the zinc deficient animals. In a series of clinical and community-based
intervention trials with zinc supplementation, it was shown that there
was a significant response, both in terms of linear growth and weight gain
to zinc supplementation. A heterogeneity of responses did appear
across studies suggesting that the initial nutritional status and initial
plasma zinc concentrations of the children contributed to the variation
and magnitude in responses.
The role of zinc in HIV infection was reviewed. Studies looking at associations
between plasma zinc concentrations, the severity of HIV infection, and
the progression of disease were reviewed and demonstrated that a negative
correlation did in fact exist. That is, more severe disease and more rapid
progression of disease was associated with lower initial plasma levels
of zinc. Results from zinc supplementation trials in patients with
HIV infection have show that zinc can either reduce the severity of HIV
infection or supplements actually can contribute to a more rapid progression
of HIV. Data was presented to show how subjects with HIV on AZT who
were administered zinc supplements had increased circulating zinc levels,
increased zinc associated thymulin levels, and decreased rates of opportunistic
infections. However, in a follow up study, a similar benefit of additional
zinc supplementation was not demonstrated, but the regimen itself however,
may be protective against zinc deficiency.
Several studies of zinc supplementation in children utilizing the statistical
method of pooled analyses were reviewed to evaluate the outcomes of diarrheal
severity. Consistent across studies was the finding that there was
a decrease in the severity of diarrheal episodes as well as a decrease
in the incidence of diarrheal episodes due to zinc supplementation.
These findings were remarkably consistent in different subgroups with regard
to initial anthropometric status, zinc status, age, and sex. In patients
with malaria, substantial reductions in malaria incidence rates were noted
in response to zinc supplementation.
Lastly, results from a meta-analysis study performed on zinc intervention
trials for upper respiratory infections were presented. The results of
ten studies were pooled and reviewed. Five studies showed a positive benefit
of zinc administration and five studies seemed to indicate that there was
no benefit of zinc therapy in the reduction of respiratory infections.
However, it was noted that substantial heterogeneity existed across the
trials, the use of multiple forms of zinc preparations, and lack of objective
outcome measures may have contributed to the failure to detect an impact
of the therapeutic regimen.