Natural Variation of Selenium in Brazil Nuts and Soils from the Amazon Region.

The Brazil nut tree (Bertholletia excelsa) is native of the Amazon rainforest. Brazil nuts are consumed worldwide and are known as the richest food source of selenium (Se). Yet, the reasoning for such Se contents is not well stablished. We evaluated genotypic variation on Se contents of Brazil nuts grown in different areas of the Brazilian Amazon, as well as soil Se contents in order to investigate if soil-Se is a major factor driving Se contents in nuts. Soil Se content (µg kg^-1) varied from <65.8 to 1372.8 (average 283.0), whereas Se in nuts (mg kg^-1) ranged from <0.55 to 362.29 (average 37.89). Selenium contents found in Brazil nuts were not correlated to soil-Se contents in the layers evaluated in the present study. Our results suggest that consumption of 1 single nut could provide 16 to 447% of the daily Se requirement for an adult. Further studies are needed to elucidate the factors underlying Se accumulation in Brazil nuts.