Researchers from Dartmouth Medical School also report significant risk reductions for moderate smokers and people with a cancer related to a specific gene – p53.
Other studies have already reported similar association between selenium and bladder cancer among women, but the new results, published in the December issue of Cancer Prevention Research, are said to be the first to show an association between selenium and p53 positive bladder cancer.
"Ultimately, if it is true that selenium can prevent a certain subset of individuals, like women, from developing bladder cancer, or prevent certain types of tumours, such as those evolving through the p53 pathway, from developing, it gives us clues about how the tumours could be prevented in the future and potentially lead to chemopreventive efforts," said lead researcher Margaret Karagas.
Selenium levels have been falling in Europe since the EU imposed levies on wheat imports from the US, where soil selenium levels are high.
As a result, average intake of selenium in the UK has fallen from 60 to 34 micrograms per day, leading to calls from some to enrich soil and fertilizers with selenium to boost public consumption. Selenium-enriched fertilizers are used in Finland.
The European recommended daily intake (RDI) is 65 micrograms. The recommended EC Tolerable Upper Intake Level for selenium is 300 micrograms per day.
Karagas and her co-workers measured selenium levels in the toenails of 767 people newly diagnosed with bladder cancer (76 per cent male, average age 62) and 1,108 people from the general population (61 per cent male, average ag 61). While no associations were found between selenium levels and bladder cancer risk for the whole population group, significant reductions in risk were found for women (34 per cent), moderate smokers (39 per cent) and those with p53 positive cancer (43 per cent).
"There are different pathways by which bladder cancer evolves and it is thought that one of the major pathways involves alterations in the p53 gene," said Karagas. "Bladder cancers stemming from these alternations are associated with more advanced disease."
The researchers noted that they hope to replicate these findings on a larger scale in order to examine the connection between selenium and bladder cancer in women and those with p53 tumours, as well as with patient prognosis.
Bladders: Maybe. Prostates: Maybe not
In a new study, published in the new issue of the American Journal of Clinical Nutrition, data from the European Prospective Investigation into Cancer and Nutrition (EPIC) study indicates that blood levels of selenium may not impact on the risk of prostate cancer.
The researchers, led by Naomi Allen from the University of Oxford, performed a nested case-control study with 959 men with incident prostate cancer and 1,059 healthy men who acted as the controls for comparison.
The concentration of selenium in the blood was not associated with the risk of developing prostate cancer. These null associations were also observed when the researchers accounted for the stage or grade of disease, and for the smoking status of the disease.
“Plasma selenium concentration was not associated with prostate cancer risk in this large cohort of European men,” concluded Allen and her co-workers.
Sources: Cancer Prevention ResearchDecember 2008, doi:10.1158/1940-6207.CAPR-08-0046"Selenium and Risk of Bladder Cancer: A Population-Based Case-Control Study"Authors: K. Wallace, K.T. Kelsey, A. Schned, J.S. Morris, A.S. Andrew, M.R. Karagas
American Journal of Clinical NutritionDecember 2008, Volume 88, Pages 1567-1575“Plasma selenium concentration and prostate cancer risk: results from the European Prospective Investigation into Cancer and Nutrition (EPIC)”Authors: N.E. Allen, P.N. Appleby, A.W. Roddam, A. Tjonneland et al.