Have you eaten your radioactive potassium for the day?

I heard from someone a while back that the bananas that we eat are radioactive. And i didnt think it was true but it is. I did some research and then this was the first time I have ever heard a banana be used as a unit of measurement. Ready for it? The Banana Equivalent Dose. BED
The BED is not actually a SI unit of measurement and is meant more satirically; Layman's terms to contrast the amount of potentially damaging radiation that one receives in eating one banana. The SI unit for measurement of radiation is the siervert which is one joule of gamma-ray energy per gram of tissue.
Banana's are not entirely unique in being radioactive though, "bananas, like most organic material, naturally contain a certain amount of radioactive isotopes—even in the absence of any artificial pollution or contamination."(1)
The BED is not a measurement of total radiation but rather specifically to organic material. Radioactivity is present in all organic material, so this is not something to be alarmed about to want to go and throw away all your banana's. What makes bananas radioactive is the radioactive isotopes present: K40. "the radioactivity of a few bananas is sufficient to trigger radiation sensors used to detect possible smuggling of nuclear material at U.S. ports."(1)
In contrast though, everything is made of chemicals and so the presence of what are called radionucleotides is something that is to be expected and is something that we obtain either through chemical biprodects of our body processes and are in the food and water we intake everyday. K40 is also not the only radioactive isotope though there is also others which are: radium 226 and uranium 238, potassium though accounts for more than the other two elements. Banana's also are not the highest contributes.
The average amount of radiation a person would experience over the course of one year is equivalent to 6.2 mSv/year. If you ate a banana today the dose equivalent is about 0.001 mSv, so you could eat alot of bananas before you added up the amount of radiation you ingest regularly every year.
The top ten radioactive food
1. Brazil Nuts
2. Lima Beans
3. Bananas
4. Carrots
5. White Potatoes
6. Low Sodium Salt
7. Red Meat
8. Beer
9. Drinking Water
10. Peanut Butter

So, in conclusion, do not fear the banana they are still good for you

Citations:
http://en.wikipedia.org/wiki/Banana_equivalent_dose
http://www.raw-food-health.net/Natural-Radiation.html
http://ryansright.com/top-10-radioactive-foods/
www.physics.isu.edu/radinf/natural.htm
http://en.wikipedia.org/wiki/Sievert