Micronutrients & recovery
Brazil nuts are an exceptionally high but highly variable source of selenium that may also deliver toxic levels of barium and radium, posing health risks if consumed regularly as a primary selenium source.
If you eat Brazil nuts for selenium, limit your intake. A few nuts can provide enough selenium but may also deliver toxic levels of barium and radioactive radium. Do not rely on them as your sole source of selenium; rotate with other foods like seafood or meat, which have more predictable selenium levels and fewer toxic co-contaminants.
Brazil nuts are the richest source of food Se, but the content is very variable... Brazil nuts are exceedingly high in barium, containing levels up to 4000 mg barium/g... It is clear that this could readily be exceeded by a modest serving of Brazil nuts. Furthermore, Brazil nuts contain small amounts of radium... this is 1000 times higher than in other foods.
Why this rating
The paper cites specific studies measuring barium and radium levels in Brazil nuts and compares them to EPA reference doses.
Source
Food-chain selenium and human health: emphasis on intake
Margaret P. Rayman · British Journal Of Nutrition · 2008
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