Nuts are an excellent food to add to your food stores. Most nuts are highly nutritious, offering plenty of protein and healthy fat, as well as some vitamins and minerals. But not every type of nut is healthy. Brazil nuts should be avoided. The following long excerpts from an article in the British Journal of Nutrition explains why:
“Brazil nuts are the richest source of food Se [selenium], but the content is veryvariable, ranging from 0•03 to 512mg/g fresh weight in the studies quoted in the companion paper by Rayman et al. Brazil nuts are harvested from an enormous area of the Amazon basin but soil levels vary … resulting in high variability in Se content. Three studies have reported a higher Se content in unshelled than shelled nuts though the reason is not known.
“Two of these studies have drawn attention to the fact that Brazil nuts are exceedingly high in barium, containing levels up to 4000mg barium/g. Lisk et al. found that a serving of three Brazil nuts (flesh weight 13•2 g), containing 290mg Se, also provided 26 mg barium. Barium can be toxic, causing gastroenteritis, muscular paralysis, K deficiency, decreased pulse rate, ventricular fibrillation and extra systoles, and 90% of the barium ingested in that study was retained in the body. The US Environmental Protection Agency’s oral reference dose for barium based on toxicological data is 0•2 mg/kg per d, which for a 75 kg individual would be 15 mg/d. It is clear that this could readily be exceeded by a modest serving of Brazil nuts.
“Furthermore, Brazil nuts contain small amounts of radium, a radioactive material. Although the amount is very small, typically about 70 (range 3–240) Bq/kg, and most of it is not retained by the body, this is 1000 times higher than in other foods. Individuals relying on Brazil nuts as their Se source, of whom there are a not-inconsiderable number, in the UK at least, should be aware both of the uncertainty surrounding the quantity of Se they may be consuming and of the fact that they may be inadvertently consuming barium in amounts exceeding the oral reference dose and radium.” (Rayman, “Food-chain selenium and human health: emphasis on intake,” British Journal of Nutrition (2008) 100, p. 255-256)
Article Source: http://www.prep-blog.com/2014/03/15/foods-to-avoid-brazil-nuts/