Zinc fights infections in seniors

A new study finds that seniors who take zinc supplements are at significantly less risk of infections, in part because of zinc’s antioxidant and anti-inflammatory effects, both of which improve immune function.

“Dietary zinc intake declines with advancing age,” said Ananda S. Prasad, MD, PhD, MACN, and lead author of the study, which was published in the American Journal of Clinical Nutrition. “Deficiency in zinc makes elderly people more susceptible to infection, in part because cell-mediated immunity depends on the mineral.”

“Zinc also functions as an antioxidant and thus can play a role in stabilization of cell membranes,” Prasad added.

In previous papers, Dr. Prasad describes how zinc affects multiple aspects of the immune system: it is involved in production of chemical messengers that affect immune function (cytokines), the development of antibody-producing white blood cells that mature in the bone marrow (B lymphocytes), and the function of natural killer cells (a type of white blood cell that attacks and kills tumor cells and protect against a wide variety of infectious organisms). These and other immune cells are negatively affected by zinc deficiency.

Prasad’s latest study was a randomized, double-blind, placebo-controlled trial in which 50 seniors (ages 55 to 87) received either zinc gluconate supplements (providing 45 mg of elemental zinc per day) or a placebo for 12 months. In addition to tracking the incidence of infections, such as colds and flu, they also tracked the blood levels of immune cells, oxidative stress markers, and plasma concentrations of zinc.

Compared with a group of younger adults, when the study started the older subjects had significantly lower blood levels of zinc, higher generation of inflammatory cells, and higher oxidative stress markers in their blood. The incidence of infections, generation of inflammatory cells, and oxidative stress markers were significantly lower in the zinc group than in the placebo group.

“We hope that our results will stimulate larger zinc trials in the elderly,” Prasad said. “Deficiency of zinc is very widespread in all ages throughout the world and may even be as prevalent as iron deficiency anemia, affecting nearly one billion people.”

It should be noted that zinc inhibits copper absorption, and can cause anemia and bone-marrow suppression if taken long-term in large amounts without copper. People taking zinc more than a few weeks, with the exception of those with Wilson’s disease, should also take a copper supplement providing 2 or 3 mg per day.

(Am J Clin Nutr 2007;85:837–44)

Jeremy Appleton, ND, CNS, is a licensed naturopathic physician, certified nutrition specialist, and published author. Dr. Appleton was the Nutrition Department Chair at the National College of Naturopathic Medicine, has served on the faculty at Bastyr University of Natural Health Sciences, and is a former Healthnotes Senior Science Editor and a founding contributor to Healthnotes Newswire. He has worked extensively in scientific and regulatory affairs in the supplement industry and is now a consultant through his company Praxis Natural Products Consulting and Wellness Services.

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