Pilot study to assess the effect of Brazil nuts on plasma selenium levels

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Selenium (Se) - an essential trace micronutrient, and green tea - the most common beverage consumed worldwide, have numerous biological properties that may protect against various cancers, including colorectal cancer (CRC). Despite promising results in preclinical settings, current clinical trial data are not convincing enough to allow general recommendation for using Se or green tea as an effective agent for chemoprevention of cancer in humans. This is a pilot study on the possible effects of Selenium (Se) in preventing bowel cancer in healthy individuals. 3 or 4 of our staff members will take part in this trial, prior to the launch of a full study once results have been gathered from this pilot study. Who is it for? This pilot study on Brazil nuts will be performed on 3 or 4 of our staff. They will take 6 Brazil nuts daily (which will provide 48 micrograms Se/day) for 4 weeks. Their blood samples (on 2 occasions) will be collected at the baseline and after intervention. We believe this pilot study will provide important information as to how many Brazil nuts will be required per day to increase plasma Se levels, as we expand the research into an upcoming, full study. Background Information There is growing evidence that a combination of dietary agents may synergistically or additively improve the chemopreventive efficacy than any single dietary agent. Our previous studies in mouse CRC model have shown that Se activate apoptosis (Cancer Res. 2008 June 15;68(12):4938-44), whereas green tea up-regulates DNA repair enzyme. Our recent animal studies have further shown that combining Se and green tea is more effective in suppressing colorectal oncogenesis than either Se or green tea alone, and is associated with regulation of genetic and epigenetic biomarkers implicated in colonic carcinogenesis (submitted to Clinical Cancer Research). Se and green tea are particularly interesting as a combination not only because they can be co-administered in the diet but also because they have potentially complementary mechanisms of action. We now plan to expand our study to human subjects and determine if a combination dietary supplementation of Se and green tea provides greater health benefits than can be achieved from a single dietary agent of Se or green tea by regulating molecular biomarkers. We have used selenium-enriched milk protein as the Se source in our previous human trials (Br J Nutr 2011 Aug;106(4):572-82). It was our intention to continue using dairy Se product for our upcoming human trial. Unfortunately, the production and supply of selenium-enriched milk protein has been stopped by Tatura Milk Industries (VIC, Australia). We have to seek an alternative Se source from food, and have decided to use Brazil nuts because it is the richest known food source of Se. A previous randomized controlled human trial has shown that 2 Brazil nuts per day (provided 53micrograms Se/day) is as effective for increasing plasma Se status as 100 micrograms Seasselenomethionine during 12 weeks of intervention, reaching maximum plasma Se levels at 6 weeks (Am J ClinNutr 2008;87:379-3840). Se concentration in Brazil nuts (supplied from Charlesworth, Australia) has recently been analysed by National Measurement Institute (Australia Government, VIC), the average Se concentration in Brazil nuts is relatively low (2.7 micrograms Se/g) compared to that of the report by Thomson et al, where the Se concentration is 6.4 micrograms Se/g (Am J ClinNutr 2008;87:379-3840).

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