MONDAY, May 16 (HealthDay News) -- A daily dose of the
antioxidant selenium doesn't appear to elevate "bad" cholesterol
levels, and may in fact prompt a very modest boost in "good"
cholesterol, a new British study reveals.
The finding comes from a six-month examination of the impact of
various dosages of the supplement on the cholesterol levels of
healthy people in England.
"The issue is that there have been an awful lot of studies, about eight, that have looked at blood cholesterol, both good and bad, and have found an association with high blood selenium," said study author Margaret P. Rayman, a professor of nutritional medicine at the University of Surrey in Guildford, England. But an association is only that; it doesn't mean one thing causes another.
"So we looked for whether selenium actually causes cholesterol to rise, and we definitively found that there wasn't an adverse effect," Rayman said. "In fact, we can safely and confidently say that, if anything, selenium had a slightly beneficial effect."
However, the safety of selenium has not been studied, and the
authors said the findings weren't significant enough to recommend
supplementation of the trace mineral. They also noted that the
results can't necessarily be applied to Americans, because of
differences in the food supply and diets of each country.
For the study, published in the May 17 issue of the
Annals of Internal Medicine, the authors focused on about 500 healthy British men and women aged 60 to 74 between 2000 and 2001.
Blood tests determined blood selenium, good cholesterol and bad
cholesterol levels at the start of the study. For six months, some
participants were assigned to take daily selenium yeast supplements
in either low, intermediate or high doses, while others were given
a dummy pill for the duration.
Noting that blood selenium levels were relatively low across the
board at the study's launch, the authors found that selenium levels
did rise as a result of supplementation, while those taking
selenium also experienced a slight drop in both bad cholesterol
(LDL) and overall cholesterol levels. Good cholesterol (HDL) levels
rose a bit solely among those assigned to the highest selenium
dosage. None of the patients experienced any serious side effects
as a result of selenium supplementation.
Rayman and her associates concluded that selenium
supplementation does not appear to have a negative impact on blood
cholesterol levels overall, and may in fact be "modestly
beneficial." High cholesterol levels can increase the risk of heart
However, she cautioned that in general such supplementation has
a minor impact and is not advisable as an effective means to combat
high cholesterol, particularly for people who already have high
blood selenium levels.
She added that the team's observations were based exclusively on
an analysis of British residents, and that the findings may not
necessarily apply in North America.
"In the U.K., people's baseline selenium levels in the blood are considerably lower than they are in the U.S.," she noted. "There are various reasons for that, including the fact that in the U.S. you have a wheat belt that means there is quite a high amount of selenium in the bread staple, which is not the case in the U.K."
"So, we can't extrapolate our findings to the U.S.," Rayman said. "And so I would caution against anybody in the U.S. increasing their selenium intake based on what we found, because we also know there's an increased risk for type 2 diabetes when you increase selenium intake if you are already at a high level of blood selenium levels."
Dr. Gregg C. Fonarow, a professor of cardiology at the
University of California, Los Angeles, said that efforts to gauge
the potential health impact of selenium have not yet demonstrated
any clear benefit attributable to the trace mineral.
"Overall, the evidence is inadequate to establish a protective role of selenium in cardiovascular disease or to recommend selenium supplementation to improve cardiovascular health," he said.
There's more on selenium at the
U.S. National Institutes of Health.