Brazil nut side effects may include selenium poisoning if you eat too many. Image Credit: Tane4kaChe/iStock/GettyImages

Brazil nuts are a good source of protein, dietary fiber, heart-healthy mono- and polyunsaturated fats, vitamins and minerals. However, they contain a potentially toxic compound that, if ingested in more than the recommended amount, could lead to health risks including poisoning. Learn why you should never binge on Brazil nuts!

Danger of Selenium Content

Brazil nuts contain a high content of the trace mineral selenium. Although selenium is needed by your body to survive, toxic amounts can be dangerous. Only a minute amount is needed to maintain its important role as an antioxidant to support your immune system and help regulate your thyroid, among other biological functions.

The amount of selenium in Brazil nuts varies slightly according to where they were grown, due to soil and other factors. The U.S. Department of Agriculture states Brazil nuts contain 544 micrograms of selenium per ounce. One ounce of Brazil nuts is equal to six kernels or 28.35 grams. In other words, one Brazil nut contains almost 96 micrograms of selenium.

How Much Selenium Is Safe?

The recommended dietary allowance of selenium for maintaining good health is:

Children, 7 months of age to 3 years, 20 micrograms

Children, 4 years to 8 years of age, 30 micrograms

Children, 9 years to 13 years of age, 40 micrograms

Adults, 14 years and over, 55 micrograms

Lactating and pregnant women, 60 to 70 micrograms

How Much Selenium Is Toxic?

Eating just one Brazil nut will put you over your recommended daily value, contributing 137 percent.

However, although unhealthy, it is unlikely this amount would cause a severe toxic reaction. The National Institutes of Health lists the tolerable upper limit level for selenium from food and supplements combined as:

Children, 1 to 3 years of age, 90 micrograms

Children, 4 to 8 years of age, 150 micrograms

Teens, 9 to 13 years of age , 280 micrograms

Adults, 14 years of age and older, 400 micrograms

NutritionFacts.org suggests that eating as few as four Brazil nuts every day may actually bump you up against the tolerable daily limit for selenium and put you at risk for toxicity. When eating Brazil nuts, take into consideration the other food sources of selenium you eat, such as fish, ham, beef, turkey and eggs. Also, if you take supplements, be sure to check the ingredients for levels of selenium and add that amount to your daily intake.

Symptoms of Selenium Toxicity

Selenium toxicity is a condition known as selenosis. An early indicator of excess intake of selenium is a garlic odor on your breath and a metallic taste in your mouth. The most common clinical signs of high selenium intake include:

Hair and nail loss or brittleness

Lesions of the skin

Nausea

Diarrhea

Skin rashes

Mottled teeth

Fatigue

Irritability

Nervous system abnormalities

More acute symptoms of selenosis are severe gastrointestinal and neurological reactions such as:

Acute respiratory distress syndrome

Myocardial infarction

Hair loss

Muscle tenderness

Tremors

Lightheadedness

Facial flushing

Kidney failure

cardiac failure

Death, in rare cases

Allergic Reactions to Nuts

A tree nut allergy is one of the most common food allergies in children and adults, according to Food Allergy Research and Education. Being a tree nut, Brazil nuts can cause a severe and potentially life-threatening allergic reaction. Even a small number of nuts can cause unpredictable symptoms, ranging from mild to severe, including:

Abdominal pain, cramps, nausea and vomiting

Facial swelling

Diarrhea

Difficulty swallowing

Itching of the mouth, throat, eyes, skin or any other area

Nasal congestion or a runny nose

Nausea

Shortness of breath

Anaphylaxis — a potentially life-threatening reaction that can send your body into shock

A tree nut allergy often lasts a lifetime with fewer than 10 percent of people outgrowing the allergy, says the American College of Allergy, Asthma and Immunology. If you are allergic to tree nuts, avoid Brazil nut toxicity by not consuming any products containing Brazil nuts, including oil and butters.

High Barium Content

Barium is a metal that is taken up into some plants from the soil. Brazil nuts have been found to contain barium in varying concentrations, depending on the geographical location. Barium intoxications are rare and frequently accidental or caused by suicidal ingestion. The result may cause muscle weakness and paralysis, damage to the heart and respiratory failure.

A study was conducted by the Journal of Analytical Toxicology to assess the safety of consuming Brazil nuts relative to the concentrations of natural barium and radium in nuts in various Brazilian regions. Ingesting as little as 0.2 gram of barium salts may be toxic in some cases, but lethal doses in humans usually range from 1 to 30 grams.

Researchers reported the level of radioactivity from radium and barium in the fruit of the Brazil nut tree to be two to four times higher that other foodstuffs in the same region. However, barium is not fully absorbed when the nuts are ingested in your body. Based on the results of the study, the conclusion was that the radioactivity present in Brazil nuts does not pose health risks for a daily ingestion of one nut.

Brazil Nuts Nutrition

Like most nuts, Brazil nuts are high in calories and fat. But if you keep your consumption to a minimum and eat only four to six nuts occasionally, they have a multitude of nutritional benefits. A serving of six Brazil nuts contains 185 calories and 4 grams of protein and only 3.5 grams, or 1 percent, of your daily value for carbs.

Six Brazil nuts also contain 18.8 grams of total fat, 4.3 grams of those being saturated fat. However, the nuts contain 6.9 grams of healthy monounsaturated fat and 5.8 grams of polyunsaturated fat. Dietary Guidelines suggest your total fat intake be limited to 20 to 35 percent of your daily caloric intake — between 44 and 78 grams — and no more than 10 percent of that should be from saturated fat.

Brazil nuts are a good source of dietary fiber, offering 8 percent DV, to help keep your digestive system healthy and contribute to lowering your cholesterol and decreasing your risk for heart disease.

Read more: What Does Fiber Do for Your Body?

More Brazil Nuts Benefits

Brazil nuts contain B vitamins, needed for many metabolic and physiological functions in your body. With 0.2 milligram of thiamine, Brazil nuts supply 12 percent of your daily value in six nuts. Thiamin plays a key role in the proper functioning of your nervous system, muscles and heart.

Brazil nuts contain folate — 2 percent DV in six nuts — especially important for pregnant women to prevent low birth weight and ensure proper development of their baby. Riboflavin helps metabolize carbs, fats and protein in your body, and a handful of six nuts offers 1 percent of your DV. Brazil nuts also provide 1 percent DV per six-nut serving of vitamin B6, crucial for the health of your eyes, heart and brain, and pantothenic acid, which helps your immune and nervous systems.

In addition to the B vitamins, Brazil nuts contain 8 percent of your DV for vitamin E, an important antioxidant to help fight disease.

All the Essential Minerals

Brazil nuts contain an abundance of minerals, in addition to selenium. A rich source of magnesium, Brazil nuts contribute 27 percent of your daily value in six pieces. Magnesium regulates protein synthesis, blood glucose control and muscle and nerve functions in your body.

Also a significant source of copper, providing 25 percent DV per six kernels, Brazil nuts can protect your brain, support your immune system and contribute to bone density. Brazil nuts also provide phosphorus — 20 percent DV — needed for healthy skin, hair, bones and teeth. Other minerals in Brazil nuts are calcium, iron, potassium, zinc and manganese.

Read more: Why Are Minerals Important to Your Diet?

Drug and Medication Interactions

If you are taking certain medications, be cautious and avoid eating too many Brazil nuts that might cause an interaction with the nut's selenium content. Selenium may worsen the effect of:

Anticoagulants

Sedatives

Herbs that inhibit coagulation (such as angelica, clove, ginger)

Selenium in Brazil nuts may weaken the effects of: