The Brazil nut (Bertholletia excelsa) is a South American tree in the family Lecythidaceae, and is also the name of the tree's commercially harvested edible seeds. It is one of the largest and longest-lived trees in the Amazon rainforest. The fruit and its nutshell – containing the edible Brazil nut – are relatively large, possibly weighing as much as 2 kilograms (4 lb 7 oz) in total weight. As food, Brazil nuts are notable for diverse content of micronutrients, especially a high amount of selenium. The wood of the Brazil nut tree is prized for its quality in carpentry, flooring, and heavy construction.

Eating peanuts and tree nuts (e.g., walnuts, almonds, and pistachios) may reduce the risk of heart disease when consumed as part of a diet that is nutritionally adequate and within calorie needs. Because nuts and seeds are high in calories, eat them in small portions and use them to replace other protein foods, like some meat or poultry, rather than adding them to what you already eat. In addition, choose unsalted nuts and seeds to help reduce sodium intakes.

Yes, Brazil nuts are very high in selenium. But they contain so much selenium that it can be unsafe to eat too many of them.

Like other vitamins and minerals, selenium has a recommended intake and a safe upper limit. Adults should get at least 55 to 70 micrograms (mcg) of selenium, but not more than 400 mcg a day.

One Brazil nut has about 70 to 90 mcg of selenium. So eating one or two Brazil nuts a day is a great way to get enough selenium. But if you eat more than a small handful of Brazil nuts, you could easily go over the upper limit.

Getting too much selenium on a regular basis can cause several problems including an upset stomach, garlic breath odor, hair loss, white blotchy nails, and mild nerve damage.