Known for its high content of selenium, Brazil nuts are a sweet, nutritional snack. Selenium is an antioxidant that has proven to protect against heart disease, and certain forms of cancer. It is also known to stimulate the immune system and slow down the aging process. Most common in the United States and the United Kingdom, Brazil nuts are especially popular during the Christmas season. These healthy nuts are often added to various recipes, and are sometimes ingredients in ice cream, nut mixes, and desserts.