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Selenium in Brazil nuts highly bioavailable

Posted Nov 22 2009 10:03pm


By David Liu, Ph. D.

SATURDAY FEB 16, 2008 (foodconsumer.org) -- Brazil nuts are known to have high levels of selenium. Selenium in Brazil nuts is now found highly bioavailable, suggesting the food is a good source of this essential mineral, according to a study led by researchers in New Zealand.

The study in this month's American Journal of Clinical Nutrition showed Brazil nuts boosted serum levels of selenium and glutathione peroxidase (GPx) - an antioxidant enzyme at least as effectively as selenium supplements.

Two Brazil nuts a day raised blood selenium levels in study subjects by about 65 percent, showed the study by Christine Thomson from the University of Otago and colleagues.

In some countries where the soil does not contain much selenium, the mineral is fortified and supplemented in food to increase intake of the mineral, which is believed to be important as an antioxidant agent.

The researchers assigned two Brazil nuts containing actually 53 micrograms of selenium, a supplement with 100 mcg of selenomethionine and a placebo to 59 New Zealanders during the 12-week study. They tested blood samples from the participants.

At the end of study, Thomson and colleagues found blood levels of selenium increased 64.2, 61.0 and 7.6 percent in subjects using the Brazil nuts, selenomethionine and placebo respectively.

Brazil nuts and selenomethionine boosted blood levels of glutathione peroxidase by 8.3 percent and 3.4 percent respectively, compared to 1.2 percent for the individuals using the placebo.

Selenium is involved in many enzymes. Deficiency of selenium can cause Keshan disease - a cardiomyopathy and Kashin-Beck disease - a disease characterized by the degeneration of particular cartilage between joints (osteoarthritis).

Sufficiency of selenium can boost the immune system and help fight against infections and cancers although studies are inconsistent. Selenium may also have something to do with cardiovascular disease and type 2 diabetes.

In addition to Brazil nuts, which contain highest levels of natural selenium, the mineral is also found abundant in shrimp, crab meat, salmon, halibut, pork, chicken and whole wheat bread.

The recommended daily allowance for selenium is 40 mcg per day for children age 9 to 13 and 55 mcg for those aged 14 or older. The RDA is 20 mcg per day for children aged 1 to 3 and 30 mcg per day for those aged 4 to 8. Gender does not make a difference. Pregnant women need 60 mcg per day while breastfeeding mothers need 70 mcg per day.
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