Believe it or not, just about all the food we consume has tiny amounts of radioactivity. Some foods contain more than others. While a small amount of it is due to nuclear fallout and industrial pollution, most of it is naturally occurring, since radioactivity is a natural phenomenon.
Brazil nuts by far are the most radioactive of all food. According to Wikipedia:
Brazil nuts contain small amounts of radium. Although the amount of radium, a radioactive element, is very small, about 1–7 pCi/g (40–260 Bq/kg), and most of it is not retained by the body, this is 1,000 times higher than in other foods. According to Oak Ridge Associated Universities, this is not because of elevated levels of radium in the soil, but due to “the very extensive root system of the tree”.
Even though Brazil nuts are a lot more radioactive compared to most foods(due to its deep, extensive roots), this doesn’t mean we should avoid them. The amount is way too small to have any permanent effects. This radioactivity in Brazil nuts is naturally occurring, not due to nuclear fallout.
Brazil nuts are an excellent source of selenium, an important mineral that some preliminary studies suggest may help prevent cancer, among other things. Fortunately, selenium deficiency is rare in most developed countries.
I think this also goes to show that eating “natural” doesn’t mean you are somehow avoiding very toxic substances. Radiation is perfectly natural, and so are lead and mercury, which are also present in trace amounts in the food and water supply. Luckily, these toxins tend to get quickly removed by the body.
While eating healthy usually means eating more “natural”(less processed foods, more whole/unprocessed foods), many health-nuts take this to extremes and buy into some form of the “naturalistic fallacy” to justify their dietary habits. This is especially true of people who follow a rawfood vegan diet, and also the followers of “paleo” diets.
At its most basic, the naturalistic fallacy means equating “natural” with being inherently good, safe, or desirable, while something “unnatural” is seen as inherently bad, or undesirable. Ask a rawfoodist to explain why they believe their diet is so much better compared to the way most people eat, and their answer ultimately boils down to: “It is more natural”. Cooked food is “unnatural”(what other animals cook their food?), so cooked food is bad; food in its raw, “natural” state is good.
This doesn’t mean there is no truth to the arguments in favor of eating raw. For instance, it is true that many nutrients are destroyed while cooking at high temperatures. On the other hand, many other nutrients are less bio-available in raw foods. It must also be noted that cooking helps destroy many anti-nutrients like oxalates or phytates that can interfere with the absorption of important minerals like iron(this is why raw spinach with its high oxalate content is a poor source of calcium and iron). This explains why you can’t eat beans raw(of course you can try to do it, but I wouldn’t advise it). While some foods like salad greens, nuts, and fruit are best eaten raw, many other foods, like legumes and grains have to be cooked.
While we should minimize our consumption of processed foods, and of both natural and synthetic toxins, we shouldn’t go overboard and panic if we discover something contains trace amounts of a toxic substance. Similarly, we shouldn’t demonize something just because it may contain something that is “unnatural”. Dogmatic black and white thinking is not helpful when it comes to healthy eating.