Everything is toxic, even oxygen. However, with a soupcon of common sense thrown into the batter, the idea is moderation. Too much of anything can lead a body to trouble. So, avoid that. Learn what 'too much of' means for any regimen or supplementation.

Brazil nuts are not 'extremely toxic.' They could be if ingested by the handful most days, but I happen to enjoy them by the bagful as they come, shelled, at Costco. I never eat nuts in great quantities for two reasons: as they age, their fats age and the become rancid, meaning an increase in arachidonic acid in the body; and they are heavy on calories, so they should be strictly limited. Any food item, once again, can be toxic, but the higher risk is that they will merely add to the undesired toxicity from a variety of ingested foodstuffs that one also eats on a regular basis. Avoiding one edible because it merely adds to the burden imposed by one's wider diet makes no sense at all.