THE RELATIONSHIP BETWEEN CANCER AND SELENIUM IN A GLOBAL ENVIRONMENT

Numerous geographical and epidemiological research projects have demonstrated an inverse relationship between selenium levels in soils and crops and cancer incidence and/or mortality. This link was first noted, by Shamberger and Frost, in 1969, in the USA.It was again confirmed by Schrauzer and colleagues in 1977. In the 27 countries tudied by these researchers there was a statistically significant inverse relationship between estimated selenium intake and cancer mortality rates. At least 56 animal studies also have examined this relationship. Of these,49 have confirmed that elevated selenium reduces the development of tumours. More recently, human field trials in China and the United States have produced significant reductions in digestive,lung and prostate cancer incidences using selenium supplements. At least five pathophysiological mechanisms have been put forward to explain the possible protective effect of selenium in carcinogenesis. It is clear, however, that bedrock geology because of variations in levels of selenium and its antagonists (mercury, cadmium and arsenic)has a major impact on local cancer mortality rates.