Zinc, an important mineral in human
health, appears to affect how the immune system responds to stimulation,
especially
Zinc deficiency could play a role in
chronic diseases such as cardiovascular disease, cancer and diabetes that
involve inflammation. Such diseases often show up in older adults, who are more
at risk for zinc deficiency.
"When you take away zinc, the
cells that control inflammation appear to activate and respond differently;
this causes the cells to promote more inflammation," said Emily Ho, a
professor and director of the Moore Family Center for Whole Grain Foods,
Nutrition and Preventive Health in the OSU College of Public Health and Human
Sciences, and lead author of the study.
Zinc is an essential micronutrient
required for many biological processes, including growth and development,
neurological function and immunity. It is naturally found in protein-rich foods
such as meat and shellfish, with oysters among the highest in zinc content.
Approximately 12 percent of people in
the U.S. do not consume enough zinc in their diets. Of those 65 and older,
closer to 40 percent do not consume enough zinc, Ho said. Older adults tend to
eat fewer zinc-rich foods and their bodies do not appear to use or absorb zinc
as well, making them highly susceptible to zinc deficiency.
"It's a double-whammy for older
individuals," said Ho, who also is a principal investigator with the Linus
Pauling Institute.
In the study, researchers set out to
better understand the relationship between zinc deficiency and inflammation.
They conducted experiments that indicated zinc deficiency induced an increase
in inflammatory response in cells. The researchers were able to show, for the
first time, that reducing zinc caused improper immune cell activation and
dysregulation of a cytokine IL-6, a protein that affects inflammation in the
cell, Ho said.
Researchers also compared zinc levels
in living mice, young and old. The older mice had low zinc levels that
corresponded with increased chronic inflammation and decreased IL-6
methylation, which is an epigenetic mechanism that cells use to control gene
expression. Decreased IL-6 methylation also was found in human immune cells
from elderly people, Ho said.
Together, the studies suggest a
potential link between zinc deficiency and increased inflammation that can
occur with age, she said.
The findings were published recently
in the journal Molecular Nutrition & Food Research.
Co-authors are
Carmen P. Wong and Nicole A. Rinaldi of the College of Public Health. The
research was supported by the Oregon Agricultural Experiment Station, Bayer
Consumer Care AG of Switzerland, and OSU.
Understanding the role of zinc in the body is
important to determining whether dietary guidelines for zinc need to be
adjusted. The recommended daily intake of zinc for adults is 8 milligrams for
women and 11 milligrams for men, regardless of age. The guidelines may need to
be adjusted for older adults to ensure they are getting enough zinc, Ho said.
There is no good clinical biomarker
test to determine if people are getting enough zinc, so identifying zinc
deficiency can be difficult. In addition, the body does not have much ability
to store zinc, so regular intake is important, Ho said. Getting too much zinc
can cause other problems, including interfering with other minerals. The
current upper limit for zinc is 40 milligrams per day.
"We think zinc deficiency is
probably a bigger problem than most people realize," she said.
"Preventing that deficiency is important."
Understanding why older adults do not take in zinc as well
is an important area for future research, Ho said. Additional research also is
needed to better understand how zinc works in the body, she said.
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