Brazil nuts are technically seeds, not nuts, but their brown nut-like casings have led most people to call them nuts. They are produced by a South American tree which tends to grow in undisturbed rain forests. Brazils are a good source of the mineral selenium, which we need to produce the active thyroid hormone. Selenium also supports immunity and helps wounds to heal. You only need three or four Brazil nuts a day to get all the selenium you require. In addition to being marketed on their own as nuts, Brazil nuts are also pressed to yield oil. The oil is rich, creamy, and very flavorful.