Good Dirt
You could call it the “vitamin E helper.”
In the e-Alert “Twilight’s Last Gleaming?” (7/13/04), I told you how a metallic trace element called selenium boosts the antioxidant power of vitamin E. And if that were all selenium did, that would be reason enough to make sure you’re getting plenty of it in your diet. But there’s much more to selenium than just being one of E’s best friends.
In previous e-Alerts I’ve told you about studies that show how selenium helps reduce the risk of prostate, liver, colorectal and esophageal cancers. In addition, selenium has superior antioxidant properties that may also help manage insulin levels.
Now a new study from the UK confirms research that reveals selenium to be an important factor in maintaining a strong immune system.
Granting immunity
The selenium content of grains, fruits and vegetables depends on the amount of selenium in the soil they’re grown in. Because the level of selenium in the soil throughout the UK is low, researchers at the University of Liverpool designed a study to examine the effect of selenium supplements on the immune system.
As reported in the current issue of the American Journal of Clinical Nutrition, the Liverpool team recruited 22 subjects who had low concentrations of plasma selenium. Over a period of 15 weeks, subjects received supplements of 50 micrograms (mcg) of selenium, 100 mcg of selenium, or a placebo.
Six weeks into the trial period, each subject was given an oral vaccine containing live attenuated poliomyelitis virus. By measuring certain systems that react to viruses (such as an increase of T cells and cytokines), researchers determined that immune response was significantly boosted in those subjects who received selenium supplements, compared to the placebo group. In addition, subjects who took selenium cleared the virus from their bodies faster than the placebo subjects.
In the conclusion to their study, the researchers state that even though supplements were effective in raising selenium to helpful levels – a daily supplement of more than 100 mcg may be necessary to provide optimal immune system response.
Highs and lows
As I’ve mentioned in previous e-Alerts, selenium comes with a warning about overdoing intake of this nutrient. And while it’s true that mega-dosing might create problems, a toxic dose of selenium is actually hard to come by.
The U.S. RDA for selenium is 55 mcg for women and 70 mcg for men, but the average diet probably falls far short of that amount. I say “probably” because selenium levels in farmland soil are often deficient. In the U.S., selenium is highly concentrated in the soil of only six states: North and South Dakota, Utah, Colorado, Montana and Wyoming. Anyone who lives in these states and eats ample amounts of locally grown fruits and vegetables daily is probably getting a good selenium intake. But the rest of us are probably not, unless we’re taking a selenium supplement.
Research into the cancer-preventive qualities of selenium indicates that a daily intake needs to be around 200 mcg to insure adequate prevention. This is well over the RDA, of course, but you would have to get more than 2,500 mcg of selenium per day for an extended period to receive a toxic amount, so the chances of getting a dangerous dose are extremely slim.
Besides fruit and vegetables, bread, fish, and meat all contain selenium. The real selenium powerhouse, however, is the Brazil nut, delivering more than 800 mcg of selenium per ounce.
UK dilemma
In the two e-Alerts I sent you earlier this week about the European Union Directive on Dietary Supplements, I told you that many key nutrients will soon not be available in supplement doses sufficient to produce a therapeutic effect. So selenium presents a perfect example of how the EU directive could impact the health of European Union citizens.
According to NutraIngredients.com, the selenium content of UK soil is so low that the selenium levels in bread-making wheats are as much as 10 to 50 times lower than similar wheats in the U.S. and Canada. In other words, most UK citizens aren’t getting nearly enough selenium in their diets. For the time being, they have the option to supplement with as much selenium as they please. But in August 2005 their government will prohibit access to large doses of selenium.
This so-called “protection” will simply make it more difficult to help prevent cancer and improve immune defense.
Sources:
“An Increase in Selenium Intake Improves Immune Function and Poliovirus Handling in Adults with Marginal Selenium Status” American Journal of Clinical Nutrition, Vol. 80, No. 1, July 2004, ncbi.nlm.nih.gov
“Lack of Selenium May Impact Immune Response” NutraIngredients.com, 6/23/04, nutraingredients.com
