This Seemingly Healthy Nut Could Be Toxic

You wouldn't think a food as objectively healthy as nuts should contain a warning on the label. But one nut in particular probably should.

Brazil nuts are one of the richest sources of selenium in the world. Selenium is a critical mineral that serves as an antioxidant to protect cells and also supports thyroid health. Like any micronutrient, however, too much can cause toxicity.

The daily recommendation for selenium intake in adults is 55mcg, with the safe upper limit being 400mcg. Toxic effects can begin around the 1,200mcg mark. Selenium toxicity can lead to things like hair loss, nerve damage, and heart problems.

A single Brazil nut can contain upwards of 80-90mcg of selenium depending on the source. This means that eating just four Brazil nuts can have you approaching the upper limit for safety.

What's even more concerning is that a study from Colorado State University found that there could be an up to 8-fold difference in selenium content in Brazil nuts in the same bag. So in reality you don't even know what you're getting on a nut-by-nut basis in a single bag.

On the bright side, the form of selenium found in Brazil nuts is good for absorption and health benefits. So long as you're careful with the serving size, you can rest assured that you're getting an absorbable form.

This isn't meant to bring fear as much as it is awareness. Most people wouldn't think that a natural food could potentially be harmful in such a small amount. Considering that one Brazil nut contains all the selenium you probably need, it's almost better to look at it as a supplement rather than a food.

Brazil nuts are genuinely nutritious and the selenium they contain is in an excellent, bioavailable form. You just can't shovel them in like you would trail mix. So long as you're mindful of your intake, you can enjoy them. As the saying goes, a little goes a long way.

Copyright 2026 The Arena Group, Inc. All Rights Reserved

This story was originally published May 14, 2026 at 8:16 AM.