Clark’s seminal paper (here) showing a 50 % reduction in cancer mortality from 200 µg per day selenium yeast has been followed by a number of other studies suggesting that selenium deficiency might be a cause of cancer. Cancer is of concern because cases are increasing and survival from treatment using Western allopathic medicine is low. Increasing dietary selenium shows the potential to prevent many forms of cancer because selenium deficiency is common. This low selenium status in many individuals is the result of changes to dietary and agricultural practices over recent decades. Traditionally whole grains were rich sources of selenium, with some crops able to provide considerable intakes of the mineral. However, over farming has depleted soils, and modern refining processes remove what little selenium is present. Therefore plasma selenium levels are falling, with the possible result that susceptible to cancer is increasing.
Prostate cancer is of concern because it is the most common form of cancer in many Western nations. That a low plasma selenium status may play a role in prostate cancer development was highlighted in a recent study published in the American Journal of Clinical Nutrition. Researchers1 performed a review of the literature on previous studies that reported on selenium status and prostate cancer incidence, and used the data contained within the papers to perform a meta-analysis. The 12 studies that matched the criteria of the researchers for the meta-analysis included 13,254 subjects and 5007 cases of prostate cancer. The results showed a dose response protective effect of selenium plasma levels against prostate cancer at plasma concentrations up to 170 ng/mL Use of studies measuring toenail selenium concentrations showed a protective effect of selenium between 0.85 and 0.94 µg/g from toenail cuttings.
These results suggest that selenium is protective of prostate cancer and support other studies that show a reduction in cancer risk with increased plasma selenium concentrations. The study data showed that reductions in the risk of prostate cancer were seen with plasma selenium concentrations of ~135 ng/mL to 170 ng/mL, but above this range no additional benefits were seen. Selenium may be protective of cancer because it is required as a co-factor for the glutathione peroxidise enzyme. This enzyme is pivotal in cellular antioxidant defences, and low intakes of selenium are known to rapidly decrease cellular levels of glutathione peroxidise. Cancer may be initiated by free radical damage to cellular components including the genetic material, and adequate glutathione peroxidise status may be necessary to reduce the effects of this damage. The low availability of selenium in the Western diet necessitates the taking of selenium supplements to achieve optimal plasma levels.
RdB
