Selenium Supplementation and Prostate Cancer

New Zeland landscape
The New Zealand study results suggest that each of us needs to take personalized selenium supplement dosages based on our individual characteristics rather than have all of us take the same 200 microg/day tablet for prostate health benefits [Karunasinghe 2019].
Demographic, dietary, genetic, and life style factors influence the prostate health effects of selenium supplementation according to New Zealand researchers.

An inverse association between serum selenium concentrations and prostate-specific antigen levels was especially strong in the following sub-groups of study participants [Karunasinghe 2019]:

  • men below the age of 55 years
  • men who never smoked
  • men carrying the GPX1 rs1050450 T allele
  • men with dietary intakes above the recommended daily intake for zinc (11 mg)
  • men with dietary intakes below the recommended daily intake for vitamin B12 (15 mcg)

Moreover, the increase in serum selenium status and the resulting post-supplementation serum selenium status were significantly dependent upon baseline serum status [Karunasinghe 2019].

The overall gain in serum selenium levels from supplementation declined at a rate of 0.828 microg/L with each one microg/L increase in baseline serum selenium level [Karunasinghe 2019]. read more

Selenium Status and Prostate Cancer Risk

The light blue ribbon is the prostate cancer awareness ribbon. Along with skin cancer, prostate cancer is the most common cancer among American men. The American Cancer Society estimates that one man in nine will be diagnosed with prostate cancer during his lifetime. Research shows that blood selenium status within a specific range is associated with reduced risk of prostate cancer.

One of the big challenges in selenium research is the optimizing of the daily selenium intake to reduce the risk of prostate cancer. We need more research results to answer the following questions about the use of selenium supplements to reduce the risk of prostate cancer [Waters & Chiang 2017]:

  • What is the optimal formulation of the selenium supplement?
  • What is the correct daily dosage?
  • What is the range of baseline blood selenium concentrations that indicates a need for selenium supplementation?
  • What is the blood selenium level above which selenium supplementation will not reduce the risk of prostate cancer further?

The idea that selenium intakes and selenium status are an important determinant of prostate cancer risk began to receive considerable attention after University of Arizona Professor Larry Clark published the results of the Nutritional Prevention of Cancer Trial in JAMA in December 1996 [Clark 1996].

High-Selenium Yeast Supplements in the Nutritional Prevention of Cancer Trial

The Nutritional Prevention of Cancer Trial (NPCT) was a supplementation trial using 200 micrograms of a selenized yeast preparation or placebo for an average duration of 4.5 years.  The study participants were 1312 men and women with an average age 63 years. read more

Blood selenium concentrations and high-grade prostate cancer

A 2012 meta-analysis and systematic review has shown an inverse association between plasma/serum selenium levels and prostate cancer advanced prostate cancer in particular. Denmark is in a low-selenium region of the world, and the Danish population as a whole has low selenium intakes and sub-optimal blood selenium levels. Danish researchers have, accordingly, investigated the association between pre-diagnostic selenium levels and the risk of total, advanced, and high-grade prostate cancer. Pictured here: the Dannebrog, Denmark’s national flag.

Higher blood selenium concentrations and higher blood selenoprotein P concentrations are significantly associated with reduced risk of high-grade prostate cancer [Outzen].

The researchers defined “advanced” prostate cancer as ≥T3 or with a Gleason-score ≥7.  They defined “high-grade prostate cancer” as cancers having a Gleason score equal to or greater than 8.

Furthermore, in survival analyses, a higher pre-diagnostic level of plasma selenium is significantly associated with a lower risk of all-cause mortality in prostate cancer patients [Outzen].

Selenium and prostate cancer in the “Diet, Cancer, and Health” cohort

These are the conclusions from an analysis of the data from the Danish “Diet, Cancer, and Health” cohort.  The cohort consists of 27,179 men living in the greater metropolitan areas of Copenhagen and Aarhus who were recruited into the study.  They were aged 50 – 64 years and had no previous record of cancer at the time of recruitment [Outzen]. read more

Selenium and prostate cancer: the toenail evidence

Meta-analyses have shown an inverse association between plasma/serum selenium concentrations and the risk of prostate cancer. The same inverse association has also been seen in three high-quality studies of toenail selenium concentrations and the risk of prostate cancer. The data from the Netherlands Cohort Study clearly show that higher toenail selenium is associated with significantly reduced risk of prostate cancer.

Analysis of data from the Netherlands Cohort Study shows that higher toenail selenium concentrations are associated with a substantial reduction in the risk of advanced prostate cancer.  Men in the highest quintile of toenail selenium had a statistically significant (p=0.001) 63% reduced risk of advanced (stage III-IV) prostate cancer compared to men in the lowest quintile of toenail selenium [Geybels].

Men in the highest quintile of toenail selenium concentrations had a toenail selenium level higher than 0.617 micrograms of selenium per gram of toenail.  Men in the lowest quintile of toenail selenium concentrations has a toenail selenium level lower than 0.469 micrograms of selenium per gram of toenail [Geybels]. read more

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. read more

Serum/plasma selenium status and protection against cancer

In cancer prevention, there seems to be a U-shaped response to selenium supplementation. The threat of adversity is greater at the lower and higher levels of serum/plasma selenium. For example, Emily Chiang and her colleagues posit that the optimal serum selenium level for the reduction of prostate cancer risk is between 119 and 137 micrograms per liter. (Graph for illustration purposes only)

The documentation in various systematic reviews and meta-analyses of selenium and cancer studies shows a significant inverse association between selenium intake and/or plasma/serum selenium status and cancer [Lee; Hurst; Cai].

There is some evidence of a U-shaped relationship between plasma/serum selenium status and protection against cancer [Hurst; Rayman].  Low plasma/serum selenium status clearly correlates with higher risk of cancer.  High plasma/serum selenium status correlates with no increased protective effect against cancer.  The key is to find the supplement doses and subsequent plasma/serum status that give the best protection in between the two extremes.

Evaluating the evidence from published studies is complicated.  We need to remember that the following factors affect the relationship between selenium status and/or intake and cancer risk: read more

Selenium and the prostate

Next to skin cancer, prostate cancer is the most common cancer in men in the United States. It is a leading causes of cancer death among men of all races and ethnic backgrounds. Low selenium status is associated with increased risk of prostate cancer.

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]. read more

Prostate cancer risk and selenium status

Selenium supplements in the form of organic high-selenium yeast tablets provide the best cancer chemo-protection. These supplements are made using the yeast species Saccharomyces cerevisiae in a selenium-enriched growth medium. The yeast cells that produce the high selenium yeast tablets are rendered inactive. They are killed off by a heating process. Strains of the same yeast species are used to brew beer and bake bread.

Selenium supplementation and the risk of prostate cancer?  What do we know?  We need to be careful in interpreting the research results that we have (and we need more research), but, yes, there is evidence for an inverse association between prostate cancer risk and selenium status [Hurst 2012].

As of this writing (April 2017), the protective effect of selenium supplementation against prostate cancer seems to be found in a relatively narrow range of plasma selenium status [Hurst 2012].  Furthermore, there seems to be a U-shaped relationship between selenium status and protection against prostate cancer.

If the concentrations of selenium in the plasma are too low, there is increased risk of prostate cancer.  This is a serious concern in many regions of the world. read more