Bertholletia excelsa, the Brazil nut, is a common South American tree known for its nut. The tree can reach up to 50 m high, making it one of the largest trees in the rainforest. The fruit can take up to 14 months to reach maturity and is encased in a capsule about the same size as a coconut. Much of the Brazil nut harvest takes place from wild collection, helping towards sustainable management of the forest. The nut is a high energy food and an exceptionally rich selenium (Se) source. The amount of selenium varies, but one-week consumption of 135 g of Brazil nut may result in daily intake of 367 to 492 μg/day, exceeding the recommended value, which is 400 μg/day.

The Brazil nut also contains gallic acid, protocatechuic acid, coumaric acid and other phenolic acids. These are well-known anti-oxidants, and the selenium is also a strong anti-oxidant. A recent clinical study showed that hemodialysis patients consuming Brazil nut effectively control NF-κB and Nrf2 in peripheral blood mononuclear cells.