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from the issue of April 17, 2008
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Study raises questions about need for selenium supplements
BY VICKI MILLER, RESEARCH
Selenium's potential health benefits have grabbed attention in recent years, and many multivitamin/mineral supplements contain this trace element. While it's an essential micronutrient, new UNL research raises questions about whether healthy people need supplemental selenium.
Researchers used UNL's PrairieFire supercomputer to genetically analyze selenium levels in mammals, fish and other vertebrates and examine evolutionary trends in selenium use in the body. This study was part of research to identify useful genetic markers, or tools, to assess selenium use and levels in vertebrates but findings highlight broader questions.
Researchers found that fish have higher levels of selenium and associated selenoproteins than humans and other mammals. This suggests that as mammals evolved from fish, their reliance on selenium decreased.
Co-authors Vadim Gladyshev, UNL biochemistry professor and director of the UNL Redox Biology Center; Alexey Lobanov, senior research associate in biochemistry at UNL; and Dolph Hatfield of the National Institutes of Health, reported results in the journal Genome Biology.
"This evolved reduced reliance on selenium raises questions about the need for selenium dietary supplements in healthy people, which is a currently accepted practice," Gladyshev said.
Selenium deficiencies are associated with several health disorders in China and other countries where the soil is low in selenium. However, Americans typically get plenty of selenium in their food, researchers said.
In the U.S. and most countries, foods provide at least the U.S. Recommended Daily Allowance of 55 micrograms. Additionally, 20 percent to 30 percent of Americans take daily multivitamin/mineral supplements, many of which contain selenium.
"Clearly, selenoprotein expression is regulated such that humans do not fully utilize the available dietary selenium," the researchers reported. It appears that the body internally regulates and balances the use of this trace element. Excess selenium is excreted.
"The evolved reduced utilization of selenium-containing proteins in mammals raises important questions in human and animal nutrition," researchers said. "It will be important to establish whether selenium dietary supplements are useful in situations where there is no established predisposition for disease."
GO TO: ISSUE OF APRIL 17
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