Zinc Supplementation May Decrease Incidence of Infections in the Elderly

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Zinc Supplementation May Decrease Incidence of Infections in the Elderly

http://www.medscape.com/viewarticle/553524?sssdmh=dm1.254720 & src=nldne

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News Author: Laurie Barclay, MD

Release Date: March 13, 2007

March 13, 2007 — Zinc supplements reduce the incidence of infection in

elderly patients, according to the results of a small, randomized,

double-blind trial reported in the March issue of the American Journal

of Clinical Nutrition.

" Zinc deficiency, cell-mediated immune dysfunction, susceptibility to

infections, and increased oxidative stress have been observed in elderly

subjects (ie, those > 55 y old), " write Ananda S. Prasad, from the Wayne

State University School of Medicine in Detroit, Michigan, and

colleagues. " Zinc is an effective anti-inflammatory and antioxidant agent. "

At a senior center, a group of 49 healthy adults aged 55 to 87 years and

inclusive of all ethnicities were randomized to zinc supplementation

(zinc gluconate, 45 mg of elemental zinc per day) or placebo orally for

12 months. Outcome measures included incidence of infections during the

study; generation of inflammatory cytokines, T helper 1 and T helper 2

cytokines, and oxidative stress markers; and plasma concentrations of

zinc at baseline and after supplementation.

Compared with a group of younger adults, the older subjects had

significantly lower baseline levels of plasma zinc, higher ex vivo

generation of inflammatory cytokines and interleukin 10, and higher

plasma oxidative stress markers and endothelial cell adhesion molecules.

Compared with the placebo group, the zinc-supplemented group had a

significantly lower incidence of infections and ex vivo generation of

tumor necrosis factor–alpha and plasma oxidative stress markers, and

significantly higher plasma zinc and phytohemagglutin-induced

interleukin 2 messenger RNA in isolated mononuclear cells.

The main limitation of this study is the small sample size.

" After zinc supplementation, the incidence of infections was

significantly lower, plasma zinc was significantly higher, and

generation of tumor necrosis factor alpha and oxidative stress markers

was significantly lower in the zinc-supplemented than in the placebo

group, " the authors write. " We hope that our results will stimulate

larger zinc trials in the elderly. "

The National Institutes of Health and Labcatal Laboratories (Paris,

France) supported this study. None of the authors have disclosed any

relevant financial relationships.

Am J Clin Nutr. 2007;85:837-844.

Clinical Context

Dietary zinc declines with advancing age in both developed and

developing countries, and zinc deficiency is associated with increased

susceptibility to infections as well as increased oxidative stress

reflected in inflammatory cytokines, such as tumor necrosis factor–alpha

and interleukin 1-beta. Zinc supplementation in healthy human subjects

has been associated with reduced concentrations of oxidative stress

byproducts. And, animal studies have demonstrated a reduction in

bacterial, fungal, viral, and parasitic pathogens in animals with zinc

deficiency.

This is a double-blind, randomized trial conducted in healthy older

adults at a senior center to determine the effect of 1 year of zinc

supplementation on rate of infections, zinc levels, and levels of

oxidative stress byproducts.

Study Highlights

* Included were healthy senior adults aged 55 to 87 years attending

a senior center and healthy young adults (mean age, 32 years) attending

a university acting as baseline controls.

* Excluded were older adults with life expectancy less than 8

months or with liver, kidney, or cardiovascular disease or cancer or

those who were self-supplementing with zinc.

* At baseline, zinc levels and assays of oxidative stress markers

were conducted in both young and older adults.

* The older adults (n = 49) were then randomized to receive either

1 capsule of zinc gluconate (15 mg of elemental zinc) orally 1 hour

before breakfast and 2 capsules before going to bed (n = 24) or

identical placebo (n = 25) for 1 year.

* Primary outcome was incidence of self-reported infections in the

older adults during 1 year, using a daily pocket calendar.

* Secondary outcomes were plasma zinc levels, percentage of cells

producing cytokines, and oxidative stress markers.

* Infections included were respiratory tract infections: the common

cold, tonsillitis, and bronchitis.

* The diagnosis of common cold was based on the presence of cough,

sore throat, hoarseness, rhinorrhea, sinus tenderness, tachypnea, or rales.

* Subjects recorded their temperatures daily and fever was documented.

* Mean age was 66 years, two thirds were women, one third used

medications, and 15% to 20% smoked or used alcohol regularly.

* Plasma zinc levels were lower in the older than in the young

adults at baseline.

* 35% of the elderly adults were considered zinc deficient at baseline.

* The percentage of cells generating cytokines was higher in

elderly subjects than in younger controls at baseline.

* Oxidative stress markers were significantly higher in older

adults than in the young controls at baseline.

* The mean incidence of infections per subject was significantly

lower in the zinc compared with the placebo group after 1 year (0.29 vs

1.4; P < .01; effect size, 1.46).

* There was a trend toward a lower incidence of the common cold in

the zinc group.

* 17 subjects in the zinc group compared with 3 subjects in the

placebo group had no evidence of infection during 1 year.

* The total number of infections in the zinc group was 7 compared

with 35 in the placebo group during 1 year.

* Plasma zinc levels were significantly higher in the zinc group at

1 year compared with the placebo group.

* Plasma molecular markers of oxidative stress showed greater

decrease in the zinc compared with the placebo group.

* The generation of inflammatory cytokines was significantly lower

in the zinc than in the placebo group.

Pearls for Practice

* Zinc supplementation at a dose of 45 mg daily in older adults is

associated with reduced incidence of respiratory tract infection during

1 year.

* One year of zinc supplementation in older adults is associated

with increased plasma zinc levels and reduced cytokine production and

serum and molecular markers of oxidative stress.

--

ne Holden, MS, RD < fivestar@... >

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