Selenium is an antioxidant mineral which plays an important role in thyroid and immune function. Some studies have also shown that selenium may have anti-cancer activity. You can get selenium from Brazil nuts, whole grains, salmon and crab. However, selenium levels among populations tend to be low, so might this be a case for taking selenium supplements, either alone, or in a multi-vitamin formulation?

The recommended intake of selenium in the UK is 75 micrograms a day for men, 60 micrograms for women. Data from the UK Total Diet Study showed that mean intake of selenium is only 48-48 micrograms a day, which is too low.

A new study aims to show what is needed to achieve optimal blood levels of selenium. Therefore a group of 199 men and women aged 50 to 64 years and living in the UK were divided into five groups for a randomized controlled trial. Four groups were given selenium supplements containing 50,100 or 200 micrograms of selenium or a placebo. Another group was given selenium-enriched onions as part of a daily meal, while the last group received the same meal without the selenium. The onions provided 50 micrograms of selenium, the same as one of the supplements. The trial continued for 12 weeks and blood levels of selenium were measured.

In all those who had consumed extra selenium either by supplement or in food, blood selenium levels went up. However, the differences in selenium levels between those consuming onion enriched with selenium and onion not enriched were not significant. By contrast, there was a significant difference in selenium levels between those consuming selenium supplements and those on placebo tablets. Comparing the 50 microgram selenium supplement group with those consuming 50 micrograms selenium through diet showed increases of blood selenium of 28.3% and 8.6% respectively. Therefore, it looks as if it is easier to get selenium into the blood via a supplement than by diet alone. On this evidence, it may be worthwhile considering adding a selenium supplement to the diet. But if you want to rely on diet to top up selenium levels, some experts suggest including 2-3 Brazil nuts a day to get sufficient of this vital mineral. Bear in mind that this is a study just on blood levels of selenium. It does not tell us what impact selenium supplementation or achieving optimal blood selenium levels might have on health and prevention of cancer.

Source:

Hurst R et al Establishing optimal selenium status: results of a randomized, double-blind, placebo-controlled trial Am J Clin Nutr 2010;91:923-31