More support for selenomethionine bioavailability
other studies that selenomethionine is more bioavailable than
selenium selenite and high-selenium yeast.
"This difference in bioavailabilities has implications for formulation of selenium supplements," wrote lead author Raymond Burk in the journal Cancer Epidemiology Biomarkers and Prevention (Vol. 15, pp. 804-810).
Selenium, a trace mineral found in soil, is understood to boost the body's antioxidant immune system detoxifier and may deliver health benefits including reduced risk of some types of cancer and cardiovascular disease and promotion of normal liver function.
The researchers randomly assigned 88 into ten groups: placebo and three doses levels (200, 400 and 600 micrograms) for each type of selenium. Selenomethionine was provided by Sabinsa, selenium selenite was purchased from Kelatron, and the high-selenium yeast was provided by Cypress Systems.
After 16 weeks, the researchers assumed that steady-state metabolism of selenium and selenomethionine was attained, and that urinary excretion was proportional to absorption.
It was found that the subjects taking the selenomethionine had a higher excretion, and therefore absorption (60 percent), than the selenite groups (41 percent), with the yeast being intermediate.
The increases were dose dependent for both selenomethionine and the yeast, but not for the selenite.
"As judged by urinary selenium excretion, selenium in the form of selenomethionine is better absorbed than selenite," concluded the researchers.
The study has been welcomed Dr Vladimir Badmaev, vice president of scientific and medical affairs, Sabinsa: "This study further substantiates the fact that selenium in the form of selenomethionine, specifically our Selenium SeLECT compound, is more available to be absorbed and used by the body.
Additionally, some of the participants had total daily intakes of more than 800 micrograms… well above the recognized safe upper limit set by the Institute of Medicine," said Badmaev.
Indeed, the Vanderbilt scientists also note this last point who said that intakes (dietary and supplementary) in the range of 800 micrograms per day could be used safely in studies of limited duration.
The current upper safe limit set by the IoM is 400 micrograms per day.
The study follows on from similar results, published last year in the American Journal of Clinical Nutrition (Vol. 81, pp. 829-834, April 2005), which reported that selenomethionine was more bioavailable than selenium selenite in a selenium-deficient Chinese population.
But Badmaev told NutraIngredients-USA.com that there were significant differences between last year's study and the new one.
Dr Badmeav noted that the Chinese population was selenium deficient while the US population was selenium replete. Also, the Chinese-based study did not look at high-selenium yeast.
"The other difference between the studies was the dose of elemental selenium. In the 2006 study, the dose was up to 800 micrograms of elemental selenium, which is much higher than the recommended total daily intake of selenium of 200-300 micrograms. However, the dose of 800 micrograms did not produce objective or subjective side effects."
In 2003 the FDA issued a qualified health claim on selenium: "Selenium may reduce the risk of certain cancers. Some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer. However, FDA has determined that this evidence is limited and not conclusive."
