Brazil nuts are native to South America, and their trees grow mostly around the riverbanks of this continent's tropical rainforests.
Like many other nuts, Brazils are very popular for their high content of healthy fats.
According to USDA Nutrient Database, at least 66% of the content of Brazil nuts is made up of fats - saturated, mono-unsaturated and poly-unsaturated. We know that healthy fats are important for the function of our immune and cardiovascular systems, among many other benefits.
These nuts also contain 14% of protein, with a whole variety of essential amino acids. And, of course, they also offer a number of vitamins and minerals: B-complex, vitamin E, calcium, magnesium, iron, zinc, selenium and a lot more. (Ref. 1)
It is interesting to note that Brazil nuts contain an unusually high concentration of selenium - they are possibly its richest dietary source, as compared to other foods. Selenium has been associated with protection against tumour development in laboratory animals. (Ref. 2)
Generally, there are no limitations as to how many Brazil nuts per day you can take.
Just bear in mind that Brazils are high in calories and adjust your intake accordingly.