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Selenium supplements 'bad for heart'

Although many Europeans don't get as much selenium as they should according to nutritionists, it's not a good idea to recommend high-dosed selenium supplements or enrich food with the mineral. Researchers at the British University of Warwick draw this conclusion in the article they published in the Journal of Nutrition. They discovered that a high level of selenium raises the concentration of bad cholesterol in the blood.

The researchers analyzed the blood of over a thousand white Britons aged between 19 and 64. They measured the subjects' selenium and cholesterol levels. They discovered that Britons with high levels of selenium in their blood such as those in the 4th quartile of the table below also have more bad LDL cholesterol in their blood. A raised LDL level is still an important predictor of heart attacks.

Selenium supplements 'bad for heart'

This relationship is shown in the graphs below: more selenium, more bad cholesterol. And the subjects with extremely high selenium levels had even less good HDL cholesterol in their blood.

Selenium supplements 'bad for heart'

The researchers don't know what mechanism is behind the relationship between cholesterol and selenium. They speculate that the body produces more selenoprotein P if it has more selenium available, and that the extra selenoprotein P ultimately causes more LDL cholesterol to be produced. But the exact relationship is not understood.

Even though the mechanism is not fully understood, the results of the study speak for themselves, claim the researchers. "The widespread use of selenium supplements or of any other strategy that artificially increases selenium status above the level required for optimal selenoprotein concentration/activity is unwarranted at the present time", they conclude.

Heavy selenium supplements are popular among natural athletes who want to boost their testosterone level. Although it's not clear whether the British research results also apply to super fit athletes, it might be an idea not to take heavy selenium supplements continuously, but to take them in cycles instead.

J Nutr. 2010 Jan;140(1):81-7.