The case for (RDA) zinc supplementation

Doug Skrecky oberonNOSPAM at vcn.bc.ca
Sat Nov 22 14:37:11 EST 2003

	Trends Pharmacol Sci. 2000 Jun;21(6):205-8
	Zinc and immunoresistance to infection in aging: new biological tools.

	Infections can cause mortality when the immune system is damaged.
The catalytic, structural (in zinc-finger proteins) and regulatory roles
of zinc mean that this ion is involved in the maintenance of an effective
immune response. Both zinc deficiency and impaired cell-mediated immunity
combine during aging to result in increased susceptibility to infection.
Dietary supplementation with the recommended daily allowance of zinc for
between one and two months decreases the incidence of infection and
increases the survival rate following infection in the elderly. This
article reviews the biochemical pathways through which zinc might act to
increase immunoresistance to infection in the elderly.

	Int J Immunopharmacol. 1995 Sep;17(9):703-18.
	Reversibility of the thymic involution and of age-related
peripheral immune dysfunctions by zinc supplementation in old mice.

	With advanced ageing the zinc pool undergoes progressive reduction
as shown by the low zinc plasma levels and the negative crude zinc
balance, both in humans and in rodents. It has been suggested that such
zinc deficiency might be involved in many age-related immunological
dysfunctions, including thymic failure. The relevance of zinc for good
functioning of the entire immune system is, at present, well documented.
In particular, zinc is required to confer biological activity to one of
the best-known thymic peptides, thymulin, which is responsible for
cell-mediated immunity. In deep zinc deficiencies, in humans and other
animals, the low thymulin levels are due not to a primary failure of the
thymus, but to a reduced peripheral saturation of thymic hormones by zinc
ions. In aged mice both a reduced peripheral saturation of the hormone
and a decreased production by the thymus were present. Oral zinc
supplementation in old mice (22 months old) for 1 month induced a
complete recovery of crude zinc balance from negative (-1.82) to positive
values (+1.47), similar to those of young animals (+1.67). A full
recovery of thymic functions with a regrowth of the organ and a
partial restoration of the peripheral immune efficiency, as measured by
mitogen responsiveness (PHA and ConA) and natural killer cell (NK)
activity, were observed after zinc supplementation. These findings
clearly pin-point for relevance of zinc for immune efficiency and suggest
that the age-related thymic involution and peripheral immunological
dysfunctions are not intrinsic and irreversible events but are largely
dependent on the altered zinc pool.

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