Brazil nuts are one of the highest natural sources of selenium – containing 1,917µg of selenium in 100g [1].

In Australia and New Zealand, the Recommended Dietary Intake (RDI) for selenium is 70µg for men and 60µg for women, and an upper level of intake has been set at 400µg/day. And it’s good to keep in mind that we only absorb around 55-70% of selenium from the foods we eat [2].

So enjoying a few Brazil nuts each day is safe – just avoid eating excessive amounts all at once!

Did you know? The daily selenium target (RDI) can be achieved with just two Brazil nuts. And around seven Brazil nuts provides the upper limit for selenium (400µg/day).

Food sources of selenium

Brazil nuts are naturally rich in selenium, but it’s also found in seafood, poultry, eggs and other plant sources, such as sunflower seeds and wheat germ.

The amount of selenium in plant sources depends on the location they are grown, as selenium levels in soil vary. For example, New Zealand soil contains low selenium levels, meaning that dietary intakes and selenium status are lower in New Zealand than in some other countries [3]. 

Why is there an upper limit of intake for selenium?

Did you know? An upper level (UL) of intake has also been set at 400µg/day of selenium, and relates to intakes from food and supplements [4].

This is based on studies from China and the US indicating that intakes of 800µg do not cause adverse effects. Studies in native populations of the Brazilian Amazon region have found blood selenium levels ranging from 103 to 1500µg with no signs or symptoms of selenium toxicity [5].

However, because of gaps in the body of evidence, a safety factor is applied – resulting in an upper limit of 400µg (equivalent to 21g or approximately seven Brazil nuts).

There is limited data about selenium toxicity in humans. But the most common side-effects are brittleness and loss of hair and nails, as well as gastrointestinal disturbance, skin rash, fatigue, irritability and nervous system abnormalities. 

The bottom line

Enjoy a few Brazil nuts each day – just don’t eat excessive amounts all at once.