Selenium

[Guest guest]

Walford discusses selenium in BYT20YD. This article discusses how

there is a fine line between too much and too little. Does any

test measure blood levels of selenium? None of mine mention it.

Diane

http://www.nlm.nih.gov/medlineplus/news/fullstory_61552.html

Moderate Selenium Levels Tied to Longer Life

NEW YORK (Reuters Health) - When it comes to the effects of selenium

on health and longevity, you may be able to get too much of a good

thing. While moderate levels of the mineral are associated with

longevity, once selenium levels climb past a certain mark, the odds of

dying from any cause, or from cancer specifically, begin to tip

upward, a new study suggests.

The study, of nearly 14,000 U.S. adults, found that higher blood

levels of selenium were linked to a lower risk of death over 12 years,

at which point the risk appears to increase.

The findings, published in the Archives of Internal Medicine, support

earlier studies linking selenium to lower risks of prostate, lung and

colon cancers. But the study also " raises the concern that high-normal

levels of selenium may be associated with an increased risk of

mortality, " write the researchers, led by Dr. Joachim Bleys of s

Hopkins University School of Public Health in Baltimore.

Selenium is a mineral that people require in small amounts; food

sources include grains, certain nuts and some meats and seafood, such

as beef and tuna.

The body incorporates selenium into proteins called selenoproteins,

which act as antioxidant enzymes; antioxidants, in turn, help

neutralize cell-damaging substances called free radicals. Some studies

have linked higher selenium levels to lower risks of certain cancers

and heart disease.

However, much of the research has been done in countries where

people's selenium levels are often fairly low.

Most Americans, by contrast, get more than the recommended amount of

selenium. While the recommended dietary allowance (RDA) is only 55

micrograms per day, the typical intake in the U.S. ranges from 60 to

220 micrograms daily.

For their study, Bleys and his colleagues used data for 13,887 U.S.

adults who took part in a government health and nutrition study. They

found that as the participants' blood levels of selenium increased,

their odds of dying during the 12-year study period declined -- but

only up to a point.

Once blood levels of selenium surpassed 130 ng/mL, the benefits

stopped accruing; and once they passed 150 ng/mL, the odds of dying

from any cause, or from cancer in particular, began to creep back up.

The findings caution against consuming too much selenium, according to

the researchers.

" Most people in the U.S. obtain adequate selenium from their diet, "

Bleys told Reuters Health, noting that outright selenium deficiency is

rare.

Given this, and the potential for adverse effects from high selenium

levels, Bleys said there is " no rationale " for recommending selenium

supplements to the general public.

It is not clear why high-normal selenium levels were tied to an

increased death risk. But in theory, Bleys explained, excess selenium

that is not incorporated into selenoproteins may actually generate

free radicals rather than fight them.

SOURCE: Archives of Internal Medicine, February 25, 2008.