Selenium deficiency in subtropical littoral pampas: environmental and dietary aspects

Se deficiency has a critical effect on human health. The littoral near Patos Lagoon in the south of Brazil is composed of Quaternary sandy deposits and nutrient-deficient soils, which contribute to Se deficiency in the surrounding environment. The average concentration of Se in littoral soils is six times lower than the metalloid deficiency threshold of 0.5 mg kg^-1 and is close to that in countries where Keshan disease is registered. The sediments in the Patos Estuary are also notably lower in Se than near-shore marine sediments. Foodstuffs produced in the littoral pampas are characterised by extremely low Se concentrations compared with the same alimentary products reported worldwide. The total daily dietary intake of Se in the region is 24 μg day^-1, which is half the Estimated Average Requirement for adults. Black beans in the local diet provide over 40% of daily Se intake. Prescriptive addition of Se to prevalent products seems the most effective solution to the problem of metalloid dietary deficiency in the region. Similar environmental conditions and significant concentration of the population in the littoral zone suggest that the problem of Se deficiency probably affects a large proportion of the population along the Atlantic coast of Brazil.