Selenium: A Mineral Marvel?

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Wednesday July 19 11:24 PM EDT

Selenium: A Mineral Marvel?

MONDAY, July 17 (HealthSCOUT) -- Depending on what you eat and where you live,

you may not be getting enough of a substance that improves fertility and may

even fight cancer and the progression of HIV to AIDS.

A review in the current issue of The Lancet calls for health professionals to

sit up and take notice of selenium, a trace mineral that is proving to play a

role in multiple aspects of health.

Review author Margaret Rayman, a professor of nutritional medicine at the

University of Surrey in Guildford, England, became interested in selenium about

three years ago, when her research into preeclampsia revealed that the pregnant

women she was studying all had low levels of selenium.

Intrigued, she did some more research, and found that selenium levels were

abnormally low in the United Kingdom. Since then, she's also found that levels

in average Europeans are significantly lower than those in North Americans.

Continuing her studies, she found that dietary consumption of selenium had been

halved in the United Kingdom over the last 20 years. That's because the country

has significantly reduced its imports of American and Canadian wheat -- which is

high in selenium -- in favor of selenium-poor European wheat.

Rayman started collecting studies. Her findings sparked interest at

international conferences, and she finally decided to publish a review that

refers to over 80 studies.

Good for HIV patients

The review reports that selenium deficiency is linked to early pregnancy loss,

male infertility, mood problems, insufficient thyroid hormone metabolism and an

increased risk of cardiovascular disease and arthritis.

And that's not all. According to Rayman, selenium's role in viral infections --

particularly HIV -- is one of the most significant lines of research. Laboratory

studies have shown that selenium is a powerful inhibitor of HIV replication, and

a study in humans showed that AIDS patients with low levels of selenium were 20

times more likely to die from an AIDS-related illness than those with healthy

levels of the mineral.

" There are some clinical trials going on at the moment to see whether giving

selenium to people who are HIV-positive can slow or halt the progression of the

disease, " says Rayman. " If that were to be the case, that would give some hope

for treating the condition in parts of the world where they can't afford

expensive drugs.

" Probably the strongest evidence in terms of selenium and health would be the

effect on cancer risk, " continues Rayman. A Harvard-based study involving 34,000

men found that men with the lowest levels of selenium had three times the

likelihood of develop advanced prostate cancer compared to those with the

highest selenium levels.

Supplements are one approach to increasing selenium levels, as well as

selenium-rich foods, like Brazil nuts, kidney, liver, crab and other shellfish.

You can go also directly to the source: the soil. North American soil is rich in

selenium and crops absorb the mineral as they grow.

Rayman is currently raising funding for the Prevention of Cancer by Intervention

with Selenium (PRECISE) trial, a study of 30,000 people in the United States,

United Kingdom, Denmark and Sweden. And in the United States, the National

Cancer Institute has recently approved funding for a 12-year, 32,000-man study

of the effects of vitamin E and selenium supplementation on the risk of prostate

cancer.

Sunde, a professor of nutritional sciences and biochemistry at the

University of Missouri in Columbia, Mo., and an expert on selenium and human

health, says that studies like the PRECISE and prostate cancer trials will

contribute to knowledge about selenium.

" Clearly, some more definitive work is needed, " says Sunde, " both to understand

what the daily dietary allowance should be, and also to understand and clearly

see whether or not additional selenium supplementation above the requirement

really has health-promoting activity. "

What To Do

Most North Americans have little to worry about. Our selenium-rich soil makes it

more likely that we get enough of the mineral.

If you think you aren't, talk to your doctor. But don't start popping selenium

like candy -- too much selenium can be toxic, causing hair loss, loss of nails

and vomiting. The NRC's Tolerable Upper Intake Level (UL) for adults is 400

micrograms per day.

The Selenium Forum provides an overview of research, and Oncolink describes how

selenium may reduce the risk of lung, colorectal and prostate cancers.

What exactly are dietary supplements? The Office of Dietary Supplements can tell

you in detail.