Brazil nuts come from a giant evergreen tree with latin name Bertholletia excelsa. The brazil nut tree grows wild in the Amazon forest, and efforts to cultivate it outside of this area have largely been unsuccessful. This is because the brazil nut tree has an unusual reproductive cycle. Brazil nuts are a great source of selenium, and this related largely to the fact that the soils it grows in are rich in selenium. One brazil nut can provide around the recommended intake for selenium, and four or so nuts can therefore provide somewhere close to optimal levels for most individuals. Those nuts grown in the Manaus-Belem region are higher in selenium than those grown in the Acre-Rondonia region. The mineral rich soils on which the brazil nut trees grow also provide high levels of other minerals, notably chromium. Brazil nuts also contain high amounts of polyunsaturated fatty acids, unlike the monounsaturated fatty acids in most other nuts. However, this makes them particularly prone to rancidity.