Posted by Larry Hoover on March 4, 2007, at 8:40:43
In reply to Re: What are some zinc rich foods?, posted by Meri-Tuuli on March 4, 2007, at 6:00:21
> Interestingly, (and I sort of knew this already, but I just did the calculations for it) a single brazil nut provides 57.5mcg of selenium, which is apparently around the recommended daily intake. I'd only need to eat 6 to get up to the 400mcg used in the acne study Nolvas quoted. Hmmm.
Not so fast. The selenium content in Brazil nuts is highly variable, and often well below published values. N.b.: a) the variability in this study (0.03 through 512.0 ppm); and b) it is remarkable that both samples (mean values) fall well below the published values I've seen in yet other analyses.
Chemosphere. 1995 Feb;30(4):801-2.
Selenium content of Brazil nuts from two geographic locations in Brazil.
Chang JC, Gutenmann WH, Reid CM, Lisk DJ.
Toxic Chemicals Laboratory, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853-7401.Brazil nuts (Bertholletia excelsa) natively contain very high concentrations of selenium. Since dietary selenium, including Brazil nuts, have been associated with protection against tumor development in laboratory animal studies, it was of interest to determine the selenium content of the nuts from different nut-growing regions of Brazil. In the work reported, 162 nuts from each of two regions (Acre-Rondonia and Manaus-Belem) were individually analyzed for selenium. The average +/- standard deviation and range of selenium concentrations in ppm, fresh weight for nuts from Acre-Rondonia and Manaus-Belem regions were, respectively, 3.06 +/- 4.01 (0.03-31.7) and 36.0 +/- 50.0 (1.25-512.0). The toxicology of Brazil nut consumption is discussed.
The great thing about Brazil nuts is that the selenium content is not free mineral ions. Apparently, it is in the most biologically useful forms as substituted amino acids, selenomethionine and selenocysteine.
J Agric Food Chem. 2002 Sep 25;50(20):5722-8.
Characterization of selenium species in Brazil nuts by HPLC-ICP-MS and ES-MS.
Vonderheide AP, Wrobel K, Kannamkumarath SS, B'Hymer C, Montes-Bayon M, Ponce De Leon C, Caruso JA.
Department of Chemistry, University of Cincinnati, Ohio 45221-0172, USA.Brazil nuts have been classified as the foodstuffs that contain the highest level of unadulterated selenium, an essential trace element that appears to prevent cancer. To date, characterization of the selenium species in brazil nuts has not yet been investigated. In this work, various sample preparation approaches, including microwave extractions and enzymatic treatments, are examined with the goal of species preservation and subsequent selenium speciation; of these approaches, an enzymatic treatment with Proteinase K proved most effective. High-performance liquid chromatography (HPLC) separation strategies and inductively coupled plasma mass spectrometry (ICP-MS) detection schemes will also be presented. Extracts are evaluated against available standards for the commercially obtainable seleno-amino acids, selenomethionine (SeMet), selenoethionine (SeEt), and selenocystine (SeCys); selenomethionine was demonstrated to be the most abundant of these seleno-amino acids. Further characterization of unidentified selenium-containing peaks is attempted by the employment of several procedures, including electrospray-mass spectrometry (ES-MS). A peptide structure was identified; however, this was considered a tentative proposal due to the large background produced by the extremely complicated brazil nut matrix.
Best,
Lar
poster:Larry Hoover
thread:738120
URL: http://www.dr-bob.org/babble/alter/20070201/msgs/738140.html