Reaching 160 feet tall and living up to 700 years, Brazil nut trees produce fruit in pristine forests, native to regions such as the Guianas, Brazil, Peru, and Venezuela. Native Amazonians cherished these behemoths for their delicious nuts, which provided them much-needed protein, fats, and other essential nutrients.

Indeed, Brazil nuts are calorie and nutrient dense. High in mono- and polyunsaturated fats, including omega-6 fatty acids, a one-ounce (6-7 nuts) serving provides about 185 calories, 5 grams of protein, and a rich supply of magnesium, phosphorous, potassium, and selenium. In fact, Brazil nuts are the highest natural source of selenium (543 mcg in 1 oz.).

A potent micronutrient, scientific evidence to date suggests that selenium might play a role in the prevention or treatment of heart disease, cognitive decline, liver disease, some types of cancer, and thyroid disease. Selenium concentrations are highest in the thyroid gland, and it has a vital role in the functioning of the gland. Just two Brazil nuts a day make it easy for most people to meet their daily selenium requirement.

Don’t go overboard on Brazil nuts—too much selenium in the diet can cause brittle nails, alopecia, rash, upset stomach, and fatigue. The Institute of Medicine of the National Academy of Sciences advises a maximum limit of 45 mcg of selenium for kids and 400 mcg for adults daily. The best way to enjoy Brazil nuts is to combine a few with other types of nuts, seeds, and raisins. Sprinkle on salad, yogurt, or blend into a smoothie.

• National Institutes of Health. "Selenium: Dietary Supplement Fact Sheet." Accessed May 2015.
• National Institutes of Health. "Selenium: Fact Sheet for Consumers" Accessed May 2015.
• Nutrition and You. "Brazil Nuts Nutrition Facts." Accessed May 2015.
• Image:  Hans-Joachim Schneider/bigstockphoto.com