are some nuts toxic? will roasting remove the toxicity? thanks
Multnomah County Oregon
Thank you for your question about nuts. Nuts that are available commercially are not toxic to humans. However, this source indicates that they may carry bacteria that prove harmful. (It has a lot of information about our most common nuts.) This food safety article describes aflatoxins, molds that grow on some raw foods, as some nuts are eaten. The mechanisms of toxicity are explained in this article.
Although they are not sold in the US, bitter almonds contain enough cyanide to be fatally toxic. These are not the same as commercially available almonds we're used to (but they contain a small amount of cyanide, too.) As recently as November, 2014, Whole Foods recalled some almond butter that contained bitter almonds from Spain and Italy, because
"A naturally occurring chemical in the almonds commonly called hydrogen cyanide but known technically as glycoside amygdalin transforms into toxic prussic acid after an almond is crushed or chewed. Hydrogen cyanide is a natural component in peach and apricot pits. Almonds are a member of the same family."
Brazil nuts contain high amounts of selenium, a necessary trace element. Six to eight Brazil nuts contain 777% of the DV (daily value) of this element, and may cause toxicity.
Finally, a small number of acute toxicities have been reported by eating betel nuts, lest you venture into Taiwan and other Asian and tropical countries.
Note that some people will be allergic to foods that don't bother other humans. The mechanism, diagnosis and treatment of allergies is discussed here. (The article also discusses the presence of nuts or nut flavoring in alcoholic beverages; and nut oils in a variety of cosmetic products. Any of these may cause allergic reactions in susceptible people.)
Macadamia nuts are toxic to dogs per the ASPCA.
Hope this is helpful.