Brazil nut

The Brazil nut tree is one of the tallest of the Amazon rainforest, reaching over forty metres. Its fruit is a hard, round, woody pod about the size of a coconut or a grapefruit, which falls to the ground and contains eight to twenty-four nuts packed together like orange segments.

Each nut is a three-sided, curved seed with a hard brown shell and a white, oily, fine-textured kernel. The flavour is creamy, mild and slightly sweet, with a rich buttery quality.

Brazil nuts are sold in-shell, shelled, blanched, chopped, as oil and as milk-like drinks. Nearly all of the nuts come from wild trees in the forest, not plantations.

Bertholletia excelsa is native to the Amazon basin of Brazil, Bolivia, Peru, Colombia, Venezuela and the Guianas. The trees grow in mature, undisturbed forest, and their pollination depends on large-bodied bees, while the agouti, a rodent, opens the pods and spreads the seeds.

Because of these ecological needs, attempts at plantations have had mixed success, and the nut remains a forest product.

The genus name honours the French chemist Claude Louis Berthollet, and the species name excelsa means lofty. The English name Brazil nut points to its origin, while in Brazil it is called castanha-do-Para after the northern state.

Indigenous Amazonian peoples have used Brazil nuts for thousands of years as a food and trade item. European explorers encountered them in the 16th and 17th centuries, and they were exported to Europe and North America via the port of Para from the 19th century on, which gave one of the English names, Para nut.

Gathering them is a seasonal job: from December to March, collectors known as castanheiros walk through the forest, collect the fallen pods and crack them with machetes. In Bolivia and Peru, nut collecting is the economic backbone of many communities, and Bolivia has become the leading exporter of shelled nuts.

Brazil nut harvesting has been promoted as a model of sustainable forest use, since it gives the forest an economic value without logging. However, tree populations are affected by deforestation, and harvest levels have been studied for their effects on regeneration.

The nuts were also a topic of research on aflatoxin contamination, which led to trade regulations in Europe.

Brazil nuts are eaten raw or roasted as a snack, chopped into granola, cakes and chocolate, or ground into nut milk, butter and flour. In Brazilian cooking, they are used in sweets, and a traditional dish uses a creamy sauce made from the nuts.

The pressed oil is used in cooking, cosmetics and haircare, and the empty pods are used as craft items and fuel. The nuts are also used in vegan cheese and dairy-free cream recipes.

Bundles of unshelled nuts can store for months in cool, dry places.

Brazil nuts are one of the richest natural sources of selenium, an essential mineral for thyroid and antioxidant enzyme function. A single nut can supply a good part of a day's requirement, and a few nuts can reach the upper limit. They also provide unsaturated fats, protein, magnesium and fibre.

Some trials show that eating a few Brazil nuts raises blood selenium levels. Evidence for disease prevention is limited.