NEW YORK (Reuters Health) – Plasma selenium concentration within a “relatively narrow” range is associated with prostate cancer risk, according to a new systematic review and meta-analysis.
“Our dose-response meta-analysis showed a decreased risk of prostate cancer over a relatively small range of plasma/serum selenium concentrations, which suggests that there is an optimal range of selenium intake and status associated with prostate cancer risk reduction,” Dr. Susan J. Fairweather-Tait of Norwich Medical School in Norfolk, UK, one of the study’s authors, told Reuters Health.
Several studies have linked selenium status to prostate cancer risk, Dr. Fairweather-Tait and her colleagues explain, “but the dose response or beneficial range of intake or status associated with the risk reduction has not been established.”
To investigate, the researchers looked at 12 studies involving 13,254 participants, including 5,007 with prostate cancer.
Their non-linear dose-response meta-analysis found risk of prostate cancer decreased with increases in plasma or serum selenium up to 170 ng/mL, the authors reported online May 30 in the American Journal of Clinical Nutrition.
Three “high-quality” studies, which looked at toenail selenium and prostate cancer risk, found risk was reduced with a concentration between 0.85 and 0.94 mcg/g.
“A plasma/serum selenium concentration of 135 ng/mL is associated with a 15% reduction in total prostate cancer risk and a 40% reduction in advanced prostate cancer risk,” Dr. Fairweather-Tait told Reuters Health by email. “Further work is required to convert status measures to recommended intakes of selenium; that is the responsibility of risk assessors (e.g., the European Food Safety Authority), and risk managers who devise public health strategies.”
Evidence to date suggests there is a U-shaped relationship between selenium status and cancer mortality, she added, “but further data are required on the high intake end of the curve.”
Low selenium status is believed to be common in the UK and Europe, given the low concentration of the mineral in the soil. “Now that we can use European (soft) wheat for bread we no longer need to import wheat from Canada (which is very high in selenium), so one of our major dietary sources of selenium (wheat flour) is much reduced, and intakes of selenium have fallen over the past 20 years,” Dr. Fairweather-Tait said.
She concluded: “Selenium appears to play a role in modifying the risk of prostate cancer initiation and progression, and when further research has been carried out to clarify dose-response relationships, there may be a therapeutic role for selenium, but for now we recommend that selenium (be) provided by foods rich in selenium, not supplements.”
Am J Clin Nutr 2012.