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].
The decline in gain indicates that some of the supplemented selenium did not replenish the serum component but took another route through the body:
- excretion
- metabolism by the gut biota to forms that reduce the rate of absorption into the circulation
- binding to toxic compounds
- uptake into other tissue including prostate tissue
- the selenomethionine component in the selenized yeast being incorporated into tissue proteins in place of methionine
New Zealand Study Design: Selenium and Prostate Cancer
The researchers gave 200 microg/day selenium as selenized yeast to 481 men for six months. The median characteristic values for the study participants were as follows:
- Age: 55 years
- BMI: 26 kg/m2
- Baseline serum selenium: 110 microg/L
- Baseline PSA level: 1.0 nanog/mL
New Zealand Study Results: Selenium and Prostate Cancer
The study data showed that the GPX1 rs1050450 TT, AKR1C3 rs12529 CG, and SEL15 rs5845 CT alleles were associated with the best correlation between the baseline and post-supplementation serum selenium levels.
This outcome suggested that the individual serum selenium carrying capacity varies with the individual’s genotype [Karunasinghe 2019].
Brief Explanation: Individual Genotype and Selenium Utilization
- Genotype is the scientific term for the genetic make-up of an individual.
- A single nucleotide polymorphism, an SNP (pronounced “snip”), is a variation at a single position in a DNA sequence among individuals.
- Whenever more than 1% of the population has a variation of a nucleotide at a specific position in the DNA sequence, the variation is classified as a SNP.
- Whenever an SNP occurs within a gene, then the gene is described as having more than one allele.
- In an earlier study, Karunasinghe et al study showed that various selenoprotein gene single-nucleotide polymorphisms may affect the efficacy of selenium utilization. These SNPs included the following selenoprotein genes [Karunasinghe 2012]:
- the glutathione peroxidase GPx1 rs1050450 and GPx4 rs713041
- the selenoproteins SEPP1 rs3877899, SEL15 rs5845, SELS rs28665122 and SELS rs4965373
- Several different SNPs in the genes for selenoproteins were seen to modify the relationships between serum selenium concentrations and DNA damage and selenoprotein antioxidant activity, on the one hand, and the requirement for selenium supplementation, on the other hand
[Karunasinghe 2012]. - In particular, the New Zealand researchers saw a significant decrease in DNA damage with increasing serum selenium concentrations among GPx1 rs1050450CC andGPx4 rs713041 TT genotype carriers up to a serum selenium level of 116 and 149 microg/L, respectively [Karunasinghe 2012].
Conclusion: Selenium Supplementation and Prostate Health Benefits
The results of the 2019 New Zealand Study show that the following variables affect the efficacy of selenium supplementation for prostate health benefits:
- age (difference between age 55 and age 69 years)
- diet (especially, intakes of zinc and vitamin B12)
- genetics (different selenoprotein alleles)
- smoking or never smoking
To the extent that it is possible, men should base the dosage of their selenium supplementation strategies on information about their personal characteristics [Karunasinghe 2019].
Lacking access to all of the information that they need, it seems desirable for men to aim for a serum selenium concentration between 100 and 150 microg/L [Karunasinghe 2012; Rayman 2012, figure 3; Rayman 2019, figure 2].
The preferred form of selenium supplement is the selenium-enriched yeast form, which contains numerous species of selenium in addition to the selenomethionine species [Richie 2014].
Sources
Karunasinghe N, Ng L, Wang A, Vaidyanathan V. Selenium Supplementation and Prostate Health in a New Zealand Cohort. Nutrients. 2019; 12(2): doi:10.3390/nu12010002.
Karunasinghe N, Han DY, Zhu S, et al. Serum selenium and single-nucleotide polymorphisms in genes for selenoproteins: relationship to markers of oxidative stress in men from Auckland, New Zealand. Genes Nutr. 2012;7(2):179-190.
Rayman MP. Selenium intake, status, and health: a complex relationship. Hormones (Athens). 2020;19(1):9-14.
Rayman MP. Selenium and human health. Lancet. 2012;379(9822):1256-1268.
Richie JP Jr, Das A, Calcagnotto AM, et al. Comparative effects of two different forms of selenium on oxidative stress biomarkers in healthy men: a randomized clinical trial. Cancer Prev Res (Phila). 2014;7(8):796-804.
The information contained in this review article is not intended as medical advice and should not be construed as such.
15 October 2020