Like all nuts, Brazil nuts are a rich source of protein, fiber, heart-healthy mono- and polyunsaturated fats, vitamins and minerals. However, their concentration of some compounds is so high, eating them regularly may cause toxicity and pose certain health risks. They may also cause potentially fatal reactions in people with a history of tree nut allergies. If you want to include Brazil nuts in your diet, talk to your doctor about how often you should eat them and how much is safe to consume.
Each ounce of Brazil nuts, about six nuts, contains 544 micrograms of the mineral selenium. The recommended dietary allowance of selenium for healthy adults is only 55 micrograms per day. If you consume more than 400 micrograms daily, the amount set as selenium's tolerable upper intake level, you may develop selenium toxicity, a condition known as selenosis. Symptoms of selenosis include hair loss, nervous system damage, skin sores and rashes, discolored teeth, diarrhea, nausea and nail brittleness or loss. In extreme cases, it may cause kidney damage, heart failure or death.
A study published in 2010 in the Journal of Nutrition reported that, out of over 1,000 research participants, those who had the highest concentration of selenium in their blood were more likely to also have elevated blood cholesterol levels. It's not yet known if excess selenium directly affects cholesterol or if it is part of another biological process that alters cholesterol levels, but the researchers concluded that consuming more selenium than the RDA may increase your risk of heart disease.
Barium is a metal that can accumulate in seafood, grains, dairy products and drinking water, as well as Brazil nuts. The barium concentration in the nuts varies with geographical location, but it may be as high as 3,000 milligrams per kilogram, or 3 milligrams of barium in every gram of Brazil nuts. The upper intake level of barium is set at 200 milligrams per day. Eating 3 ounces of the nuts, an amount equivalent to about 18 to 24 nuts, would supply you with more barium than is considered safe, in addition to toxic levels of selenium. Over time, excess barium intake may contribute to high blood pressure.
As a tree nut, Brazil nuts are a common cause of allergic reactions. Symptoms can range from mild -- nasal congestion and nausea, for example -- to severe vomiting and diarrhea, facial swelling, trouble breathing and anaphylaxis, a condition that may result in death. In addition, a 2007 report published in the Journal of Investigational Allergology & Clinical Immunology identified Brazil nuts as the cause of the first recorded case of a sexually transmitted allergic reaction. If you are allergic to any tree nut, avoid consuming Brazil nuts, Brazil nut oil or any product that may be contaminated with either.
- National Institutes of Health: Selenium
- The Journal of Nutrition: Higher Selenium Status is Associated with Adverse Blood Lipid Profile in British Adults
- IPCS InChem: Barium and Barium Compounds
- Nuts and Seeds in Health and Disease Prevention; Edited by Victor R. Preedy, et al.
- EPA: Basic Information About Barium in Drinking Water
- Food Allergy Research & Education: Tree Nut Allergies
- American College of Allergy, Asthma & Immunology: Tree Nut Allergy
- Journal of Investigational Allergology & Clinical Immunology: Dangerous Liaison - Sexually Transmitted Allergic Reaction to Brazil Nuts