The Nutritional Prevention of Cancer trial revealed that selenium enriched brewer’s yeast offered protection against certain forms of cancer, including prostate cancer.
A new study, published in the Journal of Proteomics, now goes some way to explaining those effects by indicating that selenium enrichment of yeast produces a change in 37 proteins, a number of which were described as being relevant in the carcinogenesis process.
“While the results obtained here are noteworthy because we showed differential protein expression in selenium-rich yeast, the extent to which the active forms of the yeast proteins identified can be transported intact across the intestinal barrier and the biologic effect of such proteins (or the corresponding peptides) must be determined in preclinical animal models and pilot human clinical trials before any conclusions can be made on the potential beneficial effect,” wrote the researchers, led by Professor Karam El-Bayoumy.
“It is expected that this study will stimulate future research aimed at determining how the levels of proteins differentially expressed in SEY change in the blood of human subjects during selenium supplementation.”
Selenium is an essential macronutrient, and is considered to be an antioxidant. High levels of selenium have been inversely associated with risk of developing several cancers, including bladder, prostate and thryroid.
The trace element occurs naturally in the soil and is absorbed by plants and crops, from where it enters the human food chain - either directly or through consumption of meat and other products from grazing animals.
The mineral is included in between 50 and 100 different proteins in the body, with multifarious roles including building heart muscles and healthy sperm. However, cancer prevention remains one of the major benefits of selenium, and it is the only mineral that qualifies for a Food and Drug Administration (FDA)-approved qualified health claim for general cancer reduction incidence.
Importance of selenium
A recent review paper by Joyce McCann and Bruce Ames from the Nutrition and Metabolism Center at Children’s Hospital Oakland Research Institute in Oakland (CHORI) indicated that moderate deficiency in selenium may have long-term detrimental effects (FASEB Journal, 2011, Vol. 25, pp. 1793-1814).
The new study adds to the earlier findings by providing evidence “for the first time” that selenium enriched yeast has different levels of a number of proteins than normal yeast.
The Penn State researchers used two-dimensional difference in gel electrophoresis (2D-DIGE)-tandem mass spectrometry (MS/MS) approach to perform proteomic analysis of regular or selenium-enriched yeast.
The study’s findings were welcomed by Paul Willis, chief executive officer and president of Cypress Systems, Inc., which produces the SelenoExcell branded selenium enriched yeast ingredient.
“We always believed that selenium form does make a difference and felt it is the reason why high-selenium yeast such as SelenoExcell has been effective in cancer prevention clinical trials and why other forms of selenium have not been effective in clinical trials,” he said.
“We suspect that the advantage of SelenoExcell high-selenium yeast is because of its content of multiple forms of selenium, including some that are more direct acting in anti-carcinogenesis,” added Dr Mark Whitacre, chief operating officer and chief science officer at Cypress Systems. “This newly published study from Penn State researchers supports this hypothesis.”
Source: Journal of Proteomics
4 January 2012, Volume 75, Issue 3, Pages 1018-1030
“The effect of selenium enrichment on baker's yeast proteome”
Authors: K. El-Bayoumy, A. Das, S. Russell