Combination of Selenium and Green Tea on bowel health

INTERVENTION: 30 healthy volunteers (>50yrs) at‐risk for CRC by virtue of age and /or other standard risk factors will be recruited to participate in a randomised, three cohort dietary intervention study. with a parallel design to test the effects of Se and green tea alone and in combination on molecular biomarkers for CRC prevention in the normal rectal epithelial cells. They will be instructed to maintain their usual diet during the study but to avoid supplementation with any green tea‐related food or drink (limited to <3 cups of black tea per day), and Se‐rich foods such as octopus, crab and tuna, liver and kidney or additional Brazil nuts or other nuts (except those Brazil nuts and green tea extract prescribed by us). The study will consist of dietary intervention period of 6 weeks, preceded by a run in period of 4 weeks. The volunteers will be randomised (randomisation will be computer generated) into one of three groups of 10, receiving 1) Se, supplied as Brazil nuts (6 Brazil nuts daily will provide 48micrograms Se/day); 2) Green tea, supplied as a green tea extract capsule (4 capsules daily will provide 800mg EGCG/day); and 3) Se + green tea (6 Brazil nuts daily + 4 green tea extract capsules daily (will provide 48micrograms Se/day and 800mg EGCG/day). Six Brazil nuts has been chosen because the average Se concentration (2.7 micrograms Se/g) in Brazil nuts (supplied from Charlesworth, Australia) is relatively low compared to that of the report by Thomson et al, where the Se concentration is 6.4micrograms Se/g, and average weight for one nut is 4g, 2 nuts provided 53 micrograms Se/day (Am J Clin Nutr 2008;87:379‐3840). Since the average weight of one Brazil nut (supplied from Charlesworth, Australia) is 3g, 6 Brazil nuts daily will provide 48micrograms Se/day, similar to the dose of 53micrograms Se/day. The green tea dose depends on the concentration of epigallocatechin‐3‐gallate (EGCG) per capsule, one green tea extract capsule containing 200mg of EGCG is supplied by NOW Foods, USA, 4 capsules of green tea has been chosen because it is equivelant to 4‐6 cups of green tea, which could be achieved in humans. Intake of a green tea extract capsule containing 400mg EGCG up to 2,000mg EGCG is safe in human trials (J Clin Oncol. 2009 Aug 10;27(23):3808‐14). The intervention period is 6 weeks to replicate the intervention period of our previous Se human trial (Br J Nutr. 2011 Aug;106(4):572‐582). Also 6 weeks is the time when maximum plasma Se level was achieved after supplementation of 2 Brazil nuts in a clinical human trial, where 2 Brazil nuts daily was shown to be as effective for increasing Se status as 100micrograms selenomethionine (Am J Clin Nutr 2008;87:379‐3840). Our previous studies and others have also shown that 4‐6 weeks of dietary intervention proved to be suitable to reveal changes in biomarkers in rectal biopsies (Br J Nutr 2007;98:525‐534). Immediately prior to the allocated dietary intervention and subsequently after 6 weeks of dietary intervention, blood samples will be collected and rectal biopsies (four biopsies are taken during each procedure) will be taken by sigmoidoscopic examination performed without bowel preparation. The biopsies will be performed by an experienced proceduralist who has performed these procedures previously. An initial 4 week pre‐treatment assessment period will precede the supplementation. The first blood sample will be taken at the start of this period and it will be assayed for Se to determine if the entry criterion for plasma Se is met. Brazil nuts (Berholletia excelas, family Lecythidaceae) are the richest known food source of selenium, with mean concentrations reported in the literature between 8‐83 micrograms Se/g CONDITION: Bowel Cancer SECONDARY OUTCOME: 1. Effect of combination diet (Se + green tea) on plasma Se and EGCG levels. The Brazil nut is a large nut that comes from the castanheiro de para tree in Brazil's rainforests. Each serving of about six to eight nuts contains 4 g of protein and 7 grams each of monosaturated and polysaturated fat. PRIMARY OUTCOME: Effects of combination diet (Se + green tea) on biomarkers of Wnt pathway (catenin), inflammation (COX‐2) and DNA repair (MGMT) in rectal epithelium. Rectal biopsies will be collected and examined by RT‐PCR and immunohistochemistry for the expression of these biomarkers at gene and protein levels ; We expect the combination diet will increase plasma Se and EGCG levels, increase Se levels is associated with reduced cancer risk, whereas EGCG is an bioactive compound found in green tea, that has anticancer activity. The interaction between Se and green tea might increase the bioavailability and biological activity of both Se and EGCG 2. Effect of combination diet (Se + green tea) on rectal selenoprotein expression (SeP, GPx‐1, GPx‐2mRNA). ; DNA from the rectal biopsies will be extracted, transformed to cDNA, PCR will be conducted to measure these selenoprotein gene. INCLUSION CRITERIA: Participants will be age >50 years & <75yrs Healthy, with no active bowel disease (previous history of adenoma removal >6 months ago is allowable) Plasma Se at or below 106 microgram/dL (to ensure that people with a high background Se status for whatever reason are not included in the study) Potential participants will be offered a faecal immunochemical test kit ( an “FIT”, the latest technology FOBT) to screen for the possibility for CRC. If positive, we would assist them to get follow‐up and they would not be eligible for the study while this was being clarified.