There have been some recent research results relating to selenium supplementation and prostate gland tissue. Researchers in The Netherlands have published results showing that a five-week daily intervention with a high-selenium yeast supplement, 300 micrograms daily, is associated with a down-regulation of genes that are involved with cellular growth and proliferation, with cellular immune response, and with inflammation processes. Also down-regulated by the selenium supplementation is the activity of genes involved with wound-healing [Kok 2017].
The Dutch study was a randomized, double-blinded, placebo-controlled study. Interestingly, the researchers saw the opposite effect in the placebo group. In the placebo group, there was an up-regulation of the genes involved in cellular immune response [Kok 2017].
The design of the Dutch study of selenium and prostate tissue
The researchers randomly assigned 23 men, aged 65 – 73, to an active treatment group receiving a daily selenium supplement (n=12) or to a placebo group (n=11). All 23 study participants were prostate cancer patients scheduled for diagnostic biopsies and subsequent radical prostatectomy or radiation.
The men in the active treatment group received 300 micrograms daily of selenium in the form of selenized yeast tablets (SelenoPrecise® tablets from Pharma Nord, Denmark). The men in the placebo group took non-selenized yeast tablets that did not differ in smell, taste, or appearance from the high-selenium yeast tablets. Neither the researchers nor the patients knew, until the end of the study, which study participants were receiving which preparations.
Five-week intervention with selenium
The researchers chose to do a five-week intervention because five weeks was the average time between a diagnostic biopsy and a radical prostatectomy.
The researchers collected blood samples and non-malignant prostate tissue at the beginning and at the end of the five-week intervention period. On average, the selenium supplementation increased the participants’ serum selenium levels from 81 to 185 nanograms per milliliter (micrograms per liter). The serum selenium levels of the participants in the placebo group did not increase appreciably [Kok].
The analysis of the prostate tissue
The researchers analyzed the prostate tissue for the expression of epithelial and mesenchymal bio-markers. Selenium treatment up-regulated the expression of epithelial bio-markers and down-regulated the expression of the mesenchymal bio-markers. The researchers concluded that the selenium treatment had had an inhibitory effect of selenium on the epithelial-to-mesenchymal transition (EMT).
This is important because the EMT transition enables cancer progression and metastasis.
Furthermore, the selenium treatment was associated with the down-regulation of the expression of genes that are involved in wound healing and inflammation. Both wound healing and inflammation processes are related to the EMT transition.
Conclusion from the selenium and prostate tissue study
The researchers concluded that their data show that selenium treatment on the order of 300 micrograms per day has a positive effect on processes involved in prostate cancer progression.
What the Dutch researchers were doing
Large intervention trials like the Nutritional Prevention of Cancer Trial [Clark 1996] and the Selenium and Vitamin E Cancer Prevention Trial [Lippman 2009] are tremendously expensive to organize and carry out. The Dutch researchers chose, instead, to study the mechanisms by which selenium supplementation affects the development and progression of cancer in the prostate.
They did analyses of five biological pathways that are significantly regulated by an intervention with selenium. They collected prostate tissue before the intervention began and again after five weeks of intervention. Then they compared the changes in gene expression in the tissue samples. The prostate tissue analyses led to the discovery of the inhibition, through the selenium supplementation, of activity associated with the development and progression of prostate cancer.
High-selenium yeast tablets preferred over l-selenomethionine tablets
The selenium preparation that the Dutch researchers used is a very stable patented high-selenium yeast preparation that contains 67% organic L-selenomethionine, selenium-methyl-selenocysteine, and as many as 30 additional organic selenium species. The preparation has a documented 88.7% absorption rate.
SelenoPrecise® tablets were used previously in a randomized, controlled trial of the effect of selenium supplementation on thyroid function in elderly study participants [Rayman 2008]. They are being used in the CATALYST trial, a randomized, controlled multicentre clinical trial of the effect of selenium supplementation in patients with chronic autoimmune thyroiditis [Winther 2014].
Sources
Clark, L. C., Dalkin, B., Krongrad, A., Combs, G. J., Turnbull, B. W., Slate, E. H., & Rounder, J. (1998). Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial. British Journal of Urology, 81(5), 730-734.
Kok, D. G., Kiemeney, L. M., Verhaegh, G. W., Schalken, J. A., van Lin, E. T., Sedelaar, J. M., & Afman, L. A. (2017). A short-term intervention with selenium affects expression of genes implicated in the epithelial-to-mesenchymal transition in the prostate. Oncotarget, 8(6), 10565-10579.
Lippman, S. M., Klein, E. A., Goodman, P. J., Lucia, M. S., Thompson, I. M., Ford, L. G., & Coltman, C. J. (2009). Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA, 301(1), 39-51.
Rayman, M. P., Thompson, A. J., Bekaert, B., Catterick, J., Galassini, R., Hall, E., & … Beckett, G. J. (2008). Randomized controlled trial of the effect of selenium supplementation on thyroid function in the elderly in the United Kingdom. The American Journal of Clinical Nutrition, 87(2), 370-378.
Winther, K. H., Watt, T., Bjørner, J. B., Cramon, P., Feldt-Rasmussen, U., Gluud, C., & Bonnema, S. J. (2014). The chronic autoimmune thyroiditis quality of life selenium trial (CATALYST): study protocol for a randomized controlled trial. Trials, 15115.
Disclaimer: the information presented in this article is not intended as medical advice and should not be construed as such.