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Study shows zinc absorption drops with age, linked to inflammation

By Hank Schultz , 02-Oct-2012

A study conducted on aged mice outlines the way in which zinc deficiency increases with age and links this dysfunction with increased levels of inflammation and immune system impairment.

Inflammation is linked with a variety of chronic health problems, including cancer, heart disease, autoimmune disease and diabetes. The study conducted at Oregon State University and published in the Journal of Nutritional Biochemistry, suggests that the recommended levels of zinc supplementation might have to be increased in older people in light of the evidence for a steep drop off in utilization.

 “There is a whole family of transporters that help control zinc in the body and how it goes into cells.  There is a family of 24; it is a fairly complex system.  What we found is that are a few of them that are different in an older animal compared to a young one.  If you give an older animal x-amount of zinc, they don’t seem to take it up as well as a younger one.  But we don’t really know why,” Emily Ho, PhD, an OSU professor and one of the study’s authors, told NutraIngredients-USA.

Zinc is involved in numerous aspects of cellular metabolism. It is a part of enzyme activity, plays a role in immune function, protein synthesis and wound healing.  A steady intake of zinc is required as the body has no specialized zinc storage system.

Zinc's link to inflammation

It’s still not entirely clear by what mechanism the dysregulation of the zinc transporters and resulting poor zinc utilization results in increased inflammation, Ho said.  But the link is real.

“This is one of the first studies to establish this zinc transporter mechanism and its potential clear link to inflammatory properties,” she said.

“We found that the mechanisms to transport zinc are disrupted by age-related epigenetic changes,” said Carmen Wong, an OSU research associate and co-author of this study. “This can cause an increase in DNA methylation and histone modifications that are related to disease processes, especially cancer. Immune system cells are also particularly vulnerable to zinc deficiency.” 

How much is too much?

Zinc is one of the nutrients with a clear danger of overdose and toxicity. The current RDA is 11 milligrams a day for men and 8 mg for women, with an upper limit set at 40 mg.  More than that, experts say, can interfere with the absorption of other minerals such as copper. Zinc can be obtained in the diet from seafood and meats but is more difficult to absorb from vegetables and grains.

Research at OSU and elsewhere has shown that zinc is essential to protect against oxidative stress and help repair DNA damage. In zinc deficiency, the risk of which has been shown to increase with age, the body’s ability to repair genetic damage may be decreasing even as the amount of damage is going up. 

Medical tests to determine zinc deficiency are rarely done, scientists say, and are not particularly accurate even if they are done.

Ho said older adults should look first to getting at least a baseline level of zinc in the diet or through supplementation. She went further to say that the RDA and upper safe limit might have to be revisited for older people as a result of the new data.

“The bottom line is it is really important to make sure you are getting enough zinc, especially if you are an older adult. At the minimum you should be sure you are getting the RDA,” she said.

“The thing with zinc is, if you are not absorbing much of it, the upper limit maybe should be different for an older person.”

The research was conducted by researchers in the Linus Pauling Institute at Oregon State University and the OSU College of Public Health and Human Sciences and was supported by the National Institutes of Health.  An abstract of the study can be seen here .

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