Brazil nuts can make a tasty afternoon snack, but they can be harmful if eaten in excess.

“Brazil nuts do offer small amounts of protein, fiber, and unsaturated fats to the diet. They also offer a trace mineral—selenium—to the diet,” Dana Hunnes, PhD, a senior dietician at RR-UCLA Medical Center, tells MDLinx.

 

An important nutrient

 

Selenium is an important nutrient that assists with DNA production, thyroid gland function, and protecting the body against damage caused by free radicals and infections.

National Institutes of Health Office of Dietary Supplements. Selenium: Fact Sheet for Consumers. March 22, 2021.

 

But adults only need around 55 micrograms of selenium per day, and Brazil nuts contain significantly more.

“We need very little selenium, hence [it being] called a trace mineral. One Brazil nut contains 68 to 91 micrograms of selenium, and the RDA [Recommended Dietary Allowance] for selenium is 55 micrograms per day, so one Brazil nut contains more than the daily recommendation,” Dr. Hunnes says.

 

 

Toxicity warning

 

Over time, consuming too much selenium can cause a number of health issues, such as nausea, rashes, diarrhea, irritability, discolored teeth, brittle nails or hair, loss of nails or hair, and nervous system issues.

Early indicators of chronically high selenium intake, also referred to as selenosis, are garlic-scented breath and a metallic taste in the mouth.

National Institutes of Health Office of Dietary Supplements. Selenium: Fact Sheet for Health Professionals. April 15, 2024.

 

Acute selenium toxicity can occur with high intake and cause a variety of symptoms, including acute respiratory distress syndrome, hair loss, muscle tenderness, lightheadedness, facial flushing, tremors, kidney failure, heart failure, and, in rare cases, death. 

 

“I was not personally aware that one could have too much selenium from Brazil nuts and what that means or what it might do. So, no, I would say it’s not well-known or understood. But, apparently, yes, if you eat more than five Brazil nuts—and regularly do this—you can eat too much selenium,” she tells MDLinx.

 

How much is too much?

 

In 2023, the European Food Safety Authority published a scientific opinion on the upper limit for selenium.

National Institutes of Health Office of Dietary Supplements. Selenium: Fact Sheet for Health Professionals. April 15, 2024.

 

Following a systematic review that explored the association between excess intake of selenium and clinical effects like alopecia, the panel set the upper limit at 255 micrograms per day for all adults, including lactating and pregnant people. This differs from the United States’ recommended upper limit of 400 micrograms for adults.

Dr. Hunnes argues that it’s a good reminder that nutrition can be complex and recommendations can change.

 

Dr. Hunnes advises that, if in doubt, it’s best for physicians to advise that patients limit their intake of Brazil nuts.

“I would recommend that people not eat too many Brazil nuts—perhaps no more than one or two at a time, and certainly no more than a couple per day if you eat them regularly,” she says.