Continued coverage of positive results, like the new study published in the International Journal of Urology (Vol. 13, pp. 1180-1184), could help further increase public awareness of a mineral already associated with reducing the risk of prostate and lung cancer, as well as boosting the immune system.
The European market for selenium supplements is estimated to be worth around €40m. This suggests that there is potential for food makers if they can improve consumer understanding of the mineral's benefits, with selenium-enriched products largely ignored by companies, unlike the supplements where a significant number of selenium products are available, both in combination with other nutrients and alone.
The authors, led by Eliane Kellen from the Katholieke Universiteit Leuven, carried out a population case-control study with 178 cases and 362 controls. Blood samples were taken to assess serum selenium concentrations.
After accounting for sex, age, smoking and occupational exposure, the researchers calculated that the risk of bladder cancer was slashed by 70 per cent for those people with blood levels of more than 96 micrograms per litre, compared to those with serum levels of less than 82.4 micrograms per litre.
Serum selenium levels between 82.4 and 96 micrograms per litre were associated with a 52 per cent risk reduction in bladder cancer risk.
Every 10 micrograms per litre increase in serum selenium levels was associated with a 14 per cent reduction in the risk of bladder cancer, a cancer that is diagnosed in about 336,000 people every year worldwide, and that is three times more likely to affect men than women, according to the European School of Oncology.
"This case-control study suggests an inverse association between serum selenium concentration and bladder cancer risk," concluded the researchers.
The study has a number of limitations, particularly being based on case and controls, and dietary consumption of selenium containing foods or supplements may have changed on diagnosis of the bladder cancer. Also, since the study was epidemiological no direct mechanistic study was conducted.
Significant further research is required, including more epidemiological studies and randomised controlled trials in humans, to further confirm these results, as well as investigating the underlying mechanism of how selenium appears to offer protection.
European selenium levels have been falling 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.
The European recommended daily intake (RDI) is 65 micrograms.