A newly published review and meta-analysis in The American Journal of Clinical Nutrition has suggested that biological levels of selenium that fall outside a relatively narrow “normal” range may well be associated with increased risk for prostate cancer. However, we wish to emphasize the authors’ clear staement that they do not believe that there is any evidence in support of the use of selenium supplements. Rather, they make the point that a good diet may be a more important fact in assuring “normal” biological levels of selenium. Specifically, one of the authors has been quoted by Reuters (see below) as staing that, “we recommend that selenium [be] provided by foods rich in selenium, not supplements.”
Hurst et al. set out to re-examine the evidence for any relationships between selenium intake, selenium status, and prostate cancer risk. To do this they conducted a systematic review and meta-analysis of randomized controlled trials, case-control studies, and prospective cohort studies published through September 2010. Studies appropriate for review and assessment needed to include reported measurements of selenium intake or status (plasma, serum, or toenail selenium), assessments of prostate cancer cases (number of events), and the relative risk for prostate cancer in the adult population.
Here are the core findings of this review and meta-analysis:
- 12 appropriate studies with a total of 13,254 participants and 5,007 cases of prostate cancer were identified and included.
- The risk for a diagnosis of prostate cancer decreased with increasing plasma/serum selenium levels of up to 170 ng/ml.
- Three high-quality studies included in the meta-analysis of selenium levels in samples of toenail cuttings and cancer risk indicated a reduction in prostate cancer risk (estimated RR: 0.29) with a toenail selenium concentration between 0.85 and 0.94 μg/g.
The authors are also clear that this study is only hypothesis generating and cannot currently be used to make accurate determination about “the right” levels of selenium in serum or other biological specimens to minimize risk for prostate cancer.
Additonal commentary about this study can be found on the Reuters.com web site. In an e-mail to Reuters, the senior author of the study apparently stated their finding that:
- A plasma/serum selenium concentration of 135 ng/ml is associated with
- A 15 percent reduction in total prostate cancer risk
- A 40 percent reduction in risk for advanced prostate cancer
As indicated above, there is clearly more work necessary to establish whether data of this type is truly definitive of risk for localized and advanced forms of prostate cancer over a man’s lifetime (as opposed to at a specific point in time)