Adequate Zinc Vital to Healthy Immune Response

As cold and flu season nears, now is a good time to take stock of zinc intake, because adequate zinc is essential to immune response. In a study funded by the Agricultural Research Service (ARS), a group of older adults with relatively low zinc concentrations boosted their immune function by raising their zinc levels.

Researchers gauged the boost by observing an increase in the number of T cells in blood challenged with a stimulus that mimics infectious agents. T cells are white blood cells that play a key immune role. The researchers noted that the greater the blood zinc concentrations, the greater the increase in T cells.

Simin Nikbin Meydani, director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts, led the ARS-funded study.

A previous study led by Meydani found that many nursing-facility residents had low blood zinc concentrations. There was a 50-percent greater incidence of pneumonia among those with low zinc levels than among those with normal zinc levels.

For the newer study, researchers recruited participants 65 or older from Boston-area nursing facilities. Again, more than 30 percent of participants tested low in zinc.

The researchers divided the zinc-deficient participants into two groups. For 3 months, one group consumed 30 milligrams (mg) of additional zinc via a daily multivitamin supplement, and a control group received a similar supplement that contained 5 mg of zinc. While the recommended dietary intake is 8-11 mg daily, the higher level was used because many volunteers had low blood zinc levels.

The researchers then retested the participants' blood zinc levels and T cell numbers. They found that the participants who took 30 mg of supplemental zinc had higher blood zinc concentrations and higher T-cell counts than those in the control group.

The researchers also challenged the participants' T cells in a test tube with a stimulus similar to a microbial infection. The T cells from the higher blood-zinc group proliferated better when challenged than those from the low-zinc group.

Good sources of zinc include oysters and other shellfish, fortified breakfast cereals, beef, pork, and beans. A personalized nutrient-intake assessment, which includes a zinc-intake audit, is available free from the USDA at www.supertracker.usda.gov.

The study results were published in the March 2016 issue of American Journal of Clinical Nutrition.—By Rosalie Marion Bliss, ARS Office of Communications.

“Adequate Zinc Vital to Healthy Immune Response” was published in the September 2016 issue of AgResearch Magazine.