Selenium for boosting immune system function


You could call it the vitamin E helper. As I’ve mentioned before, the metallic trace element, selenium boosts the antioxidant power of vitamin E… and even if that was all selenium did, it would still 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 vitamin E’s best friends.

Numerous studies have shown how selenium can help reduce the risk of prostate, liver, colorectal and oesophageal cancers. In addition, this trace mineral has superior antioxidant properties that may help manage insulin levels and promote a healthy 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. However, the level of selenium in the soil throughout the UK is very low, which  is why many of people in the  UK may be deficient of this trace mineral without even knowing it… losing out on all its immune-protective properties. This is why  researchers at the University of Liverpool designed a study to examine the effect of selenium supplements on the immune system.

As reported in 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 their conclusion, the researchers said 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 mentioned before, selenium comes with a warning: Mega-dosing might create problems. However, a toxic dose of selenium is very hard to come by.

Research into the cancer-preventive qualities of this trace mineral have shown that a daily intake  of around 200 mcg is needed to ensure adequate prevention. For instance, a 1996 study by Dr. Larry Clark of the University of Arizona showed just how effective selenium can be in protecting against cancer. In the study of 1,300 older people, the occurrence of cancer among those who took 200 mcg of selenium daily for about seven years was reduced by 42 per cent compared to those given a placebo. Cancer deaths for those taking this essential trace mineral were cut almost in half, according to the study that was published in the Journal of the American Medical Association.

Of course, a 200 mcg dose selenium is well over the government recommended daily allowance (RDA) of 55 mcg for adults. However, 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, is the Brazil nut, delivering more than 544 mcg of selenium per ounce… which is above the tolerable upper intake level (UL) of 400 mcg per day, for adults. The UL is set by The Food and Nutrition Board (FNB) of the US Institute of Medicine, which has used extensive data from studies in China to establish the required and safe levels of selenium for humans. Adverse effects were observed at daily dietary selenium intakes between about 600 and 1,600 mcg. The maximum safe dietary selenium intake was calculated to be about 800 mcg/day, but may be as low as 600 mcg in some individuals. In 2000, the FNB set the UL for selenium at 400 mcg/day, which was selected to protect sensitive individuals.

UK dilemma

We’ve been sending you regular updates on the European Union Directive on Dietary Supplements, and have 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, 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 US and Canada.

In other words, most UK citizens aren’t getting nearly enough selenium in their diets. For the time being, you still have the option to supplement with a good quality selenium supplement. However,  if you feel you need more than the RDA, don’t exceed the tolerable UL, which is 400 mcg for adults, 280 mcg for children between  9-13 and  150 mcg for children between  4-8. The UL also includes selenium obtained from food, which averages about 100 mcg per day for adults.

Disclaimer: Bear in mind the material contained in this article is provided for information purposes only. We are not addressing anyone’s personal situation. Please consult with your own physician before acting on any recommendations contained herein.


** Article first published in December 2004. Updated: November 2011 **

Prospective study of serum selenium concentrations and esophageal and gastric cardia cancer, heart disease, stroke, and total death, published, American Journal of Clinical Nutrition, Vol. 79, No. 1, 80-85, January 2004

Effects of Selenium Supplementation for Cancer Prevention in Patients With Carcinoma of the Skin: A Randomized Controlled Trial, published JAMA: 12/24/96

Micronutrient Information Center: Selenium, published online at The Linus Pauling Institute,

The New Recommendations for Dietary Antioxidants: A Response and Position Statement by the Linus Pauling Institute, published online,


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