Selenium and the prevention of prostate cancer: meta-analysis

There are many risk factors associated with the development of prostate cancer: age, family history, geographic region, insulin growth factor, nationality, and race. One risk factor that merits investigation is the relationship between blood selenium concentrations and prostate cancer risk.

Quote: “Selenium most probably has a protective role against the development of prostate cancer and its progression to advanced stages. Therefore, selenium supplementation can be proposed for prevention of prostate cancer.”

These words are taken from the conclusion of a 2018 systematic review and meta-analysis of studies of the association between selenium and prostate cancer [Sayehmiri].

The meta-analysis is based on the data from 38 journal medical articles that included 36,419 prostate cancer cases and 105,293 healthy controls. There were 22 case-control studies, 6 cohort studies, and 10 randomized controlled trials included in the meta-analysis [Sayehmiri].

Selenium levels associated with risk of prostate cancer

The pooled relative risk from the 38 studies of the association of selenium concentration and prostate cancer risk showed a statistically significant 14% risk reduction with higher levels of blood selenium or toe nail selenium.

Of the 38 studies, 10 studies investigated the relation between advanced prostate cancer and selenium. The data from these 10 studies showed a statistically significant 33% risk reduction.

Earlier meta-analyses of selenium and prostate cancer risk

Etminan 2005

The results of the 2018 Sayehmiri meta-analysis re-affirm the results of the 2005 meta-analysis done by Etminan et al.
Etminan’s meta-analysis included the data from 16 studies – 11 cohort studies and 5 case-control studies – and showed a statistically significant 26% risk reduction with moderate intakes of selenium.
The Etminan study showed a dose-response trend when the studies were stratified by disease severity.
The results suggested that selenium intake may reduce the risk of prostate cancer [Etminan].

Hurst 2012

Hurst et al included 12 studies with 5007 cases of prostate cancer and a total of 13,254 participants.
The data derived from plasma or serum selenium concentrations showed that the risk of prostate cancer decreased with increasing plasma/serum levels up to 170 micrograms of selenium per liter [Hurst].
The safest range for potential reduction of the risk of prostate cancer seemed to be the plasma selenium concentration range from 120 to 170 micrograms of selenium per liter [Hurst].

Summary: selenium concentration and prostate cancer

Prostate cancer is now the most common type of cancer world-wide. In the United States, the lifetime risk of this disease is 1 in 6 men [Sayehmiri].
There has been a lack of consensus regarding the efficacy of selenium supplementation in the prevention of prostate cancer largely because of the results of SELECT study in which a synthetic form of selenium was used instead of an organic form [Schrauzer].
Meta-analysis is a statistical technique for combining the results of several studies to arrive at a single result. It is a strategy for finding the common ground among many studies [Sayehmiri].
The present meta-analysis re-affirms the findings of a 2016 meta-analysis of selenium exposure and cancer risk, which found that high selenium exposure decreased the risk of breast cancer, lung cancer, esophageal cancer, gastric cancer, and prostate cancer, but it was not associated with colorectal cancer, bladder cancer, and skin cancer [Cai].

Concluding remarks: selenium and cancer

The last word goes to the Swedish researcher Dr. Mikael Björnstedt, Karolinska University Hospital, Stockholm, Sweden, who says that the selenium-dependent antioxidant enzymes are unique among the antioxidants. Dr. Björnstedt adds that a great body of evidence shows the potential of selenium in the large-scale general prevention of human cancers. Prevention is exerted through several different complex mechanisms and in all stages of the carcinogenic process.

Sources

Cai, X., Wang, C., Yu, W., Fan, W., Wang, S., Shen, N., & Wang, F. (2016). Selenium Exposure and Cancer Risk: An Updated Meta-analysis and Meta-regression. Scientific Reports, 619213.

Etminan, M., FitzGerald, J. M., Gleave, M. & Chambers, K. (2005). Intake of selenium in the prevention of prostate cancer: a systematic review and meta-analysis. Cancer Causes Control, 16, 1125-31.

Hurst, R., Hooper, L., Norat, T., Lau, R., Aune, D., Greenwood, D. C., & Fairweather-Tait, S. J. (2012). Selenium and prostate cancer: systematic review and meta-analysis. The American Journal of Clinical Nutrition, 96(1), 111-122.

Sayehmiri, K., Azami, M., Mohammadi, Y., Soleymani, A. & Tardeh, Z. (2018). The association between selenium and prostate cancer: a systematic review and meta-analysis. Asian Pac J Cancer Prev, 19 (6), 1431-1437.

Schrauzer, G. N. (2009). Selenium and selenium-antagonistic elements in nutritional cancer prevention.
Critical Reviews in Biotechnology, 29, 1, 15.

The information presented in this review article is not intended as medical advice and should not be construed as such.

Milestones in early selenium research

1817 Swedish chemist Jöns Jakob Berzelius discovers selenium

1957 Biochemist Klaus Schwarz shows that selenium in microscopic amounts has a vital importance for mammalian health

1969 Professor J.T. Rotruck discovers that selenium has a biochemical role as a component of the antioxidant enzyme glutathione peroxidase

1969 Professors R.J. Shamberger and D.V. Frost report a possible protective effect of selenium against cancer in humans

1973 Professor J.T. Rotruck identifies the enzyme glutathione peroxidase as a selenium-dependent protein

1977 Professor G.N. Schrauzer publishes cancer mortality correlation studies showing an inverse correlation between dietary intakes of selenium and cancer mortality in 27 countries

1988 Professor G.Q Yang summarizes the lessons learned about the selenium-related endemic diseases Keshan disease and Kashin-Beck disease and about the importance of adequate daily selenium intakes

1989 Professor G.G. Duthie publishes evidence for a role of selenium in the prevention of cardiovascular disease

1993 Researcher W.J. Blot publishes the results of the Nutrition Intervention Trials in Linxian, China, showing that supplementation with a combination of selenium and other antioxidants reduces the risk of cancer

1994 Professor G.N. Schrauzer publishes evidence that selenium is important in the maintenance and therapy of HIV-infected patients

1996 Professor Larry Clark publishes the results of a randomized controlled trial – the Nutritional Prevention of Cancer study -- that shows selenium's cancer-protective effects on colon cancer, lung cancer, and prostate cancer

1997 Professor G.F. Combs summarizes the evidence for the protective effects of selenium against cancer

1999 Professor J.E. Oldfield publishes his Selenium World Atlas, mapping areas of selenium deficiency around the world

2000 Researcher O.A. Levander publishes evidence showing an anti-viral effect of selenium

2002 Researcher R. Gärtner shows that supplementation with selenium reduces inflammation in patients with autoimmune thyroiditis

2002 Researcher Margaret Rayman presents the arguments for increasing selenium intakes to realize selenium’s antioxidant and anti-viral and anti-inflammatory effects as well as selenium’s enhancement of immune function and reproductive success.