Diary of Unknown Symptoms

Mystery of the Internal Vibration

Entry for May 20, 2007

Brazil nuts’ selenium storing secrets revealed?

19 October 2006

Brazil nuts are a rich source of selenium, an essential trace element, and now scientists have identified 15 selenium-containing peptides in the tasty treats.

The discovery should help them to understand why Brazil nuts are so good at accumulating selenium.

Selenium is believed to offer protection against heart disease and to help prevent cancer particularly of the prostrate. It is also a powerful antioxidant – meaning that it can protect cells from free radical damage. Brazil nuts are one of the best sources of selenium containing about 2500 times as much as any other nut.

The selenium peptides were by identified by Ryszard Lobinski and colleagues from the University of Pau and the Adour, France, who have detected, fragmented and sequenced 15 new selenium peptides from Brazil nuts.

Lobinski started by breaking down the Brazil nut proteins using the digestive enzyme trypsin. He then used two stages of size exclusion chromatography coupled with ICP (inductively coupled plasma) mass spectrometry (MS) to purify and concentrate the selenium-containing compounds.

In the next step, the researchers used two mass spectrometry techniques in parallel. The first – based on ICP – allowed the researchers to work out how long it took the peptide to pass through a chromatography column. Using this information, the team then used a second technique – electrospray ionisation – to pick out characteristic selenium isotope patterns of the peptides. They could then fragment and sequence these peptides to identify them.

Sam Houk from the Iowa State University, Ames, US, said, ‘this is an excellent example of the value of element-specific information from ICP-MS combined with molecular information from ESI-MS in studies of proteins or peptides with heteroatoms. Neither technique alone could identify these seleno proteins.’

May 20, 2007 Posted by | Health | , | Leave a comment

Entry for May 20, 2007

Brazil nuts: an effective way to improve selenium status

From the Department of Human Nutrition, University of Otago, Dunedin, New Zealand

Background: Brazil nuts provide a rich natural source of selenium, yet no studies have investigated the bioavailability of selenium in humans.

Objective: We investigated the efficacy of Brazil nuts in increasing selenium status in comparison with selenomethionine.

Design: A randomized controlled trial was conducted with 59 New Zealand adults. Participants consumed 2 Brazil nuts thought to provide 100 µg Se, 100 µg Se as selenomethionine, or placebo daily for 12 wk. Actual intake from nuts averaged 53 µg Se/d (possible range: 20–84 µg Se). Plasma selenium and plasma and whole blood glutathione peroxidase (GPx) activities were measured at baseline and at 2, 4, 8, and 12 wk, and effects of treatments were compared.

Results: Plasma selenium increased by 64.2%, 61.0%, and 7.6%; plasma GPx by 8.3%, 3.4%, and –1.2%; and whole blood GPx by 13.2%, 5.3%, and 1.9% in the Brazil nut, selenomethionine, and placebo groups, respectively. Change over time at 12 wk in plasma selenium (P < 0.0001 for both groups) and plasma GPx activity in the Brazil nut (P < 0.001) and selenomethionine (P = 0.014) groups differed significantly from the placebo group but not from each other. The change in whole blood GPx activity was greater in the Brazil nut group than in the placebo (P = 0.002) and selenomethionine (P = 0.032) groups.

Conclusion: Consumption of 2 Brazil nuts daily is as effective for increasing selenium status and enhancing GPx activity as 100 µg Se as selenomethionine. Inclusion of this high-selenium food in the diet could avoid the need for fortification or supplements to improve selenium status.

May 20, 2007 Posted by | Health | , | Leave a comment


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