Personally, I wouldn’t be afraid that someone could die of a banana overdose. Although the “banana equivalent” is given as an auxiliary unit describing radiation, I do not think that its value reflects the real effect of the banana on the increase in radiation in our body. In the case of a banana, the radiation is caused by an isotope of potassium which breaks down into other elements and releases ionizing radiation. But in order for this radiation to be released in our body, the amount of the radioactive isotope potassium in our body would have to increase due to the ingestion of the banana. In my opinion, this (although I’m not a biologist) does not happen, because unused potassium is eliminated from the body. For a similar reason, iodine tablets are used — by keeping the level of iodine in the body at a certain value, we will not store a possible radioactive isotope of iodine in the thyroid gland, and even if it enters our body, it will be eliminated. But if we wanted to calculate the lethal portion of bananas for fun, we would start from the above banana equivalent, which is 0.1 microSieverts (0.1 µS).

It is stated that the lethal dose is 1 Sv, with the condition that it is a dose all at once (in a very short time). This means that we would have to eat 10,000,000 bananas in a very short time, which is certainly not realistic. The limit for radiation sickness is 4,000,000 bananas (400 µSv). But we can use the banana equivalent to show other ways of irradiating. For example, in 1 day we (on an average) are exposed to a dose of radioactive radiation corresponding to the consumption of 100 bananas, an X-ray of teeth corresponds to a dose of 50 bananas, a five-hour flight corresponds to 500 bananas. In the USA, the annual exposure limit per radiation worker (e.g. a doctor at an X-Ray, a nuclear power plant employee) is 500,000 bananas. Let me just add that the banana is not the most radioactive food (I found Brazil nuts, which are about 2 times more radioactive). And the very contribution of bananas to human exposure is minimal compared to the so-called background environment (i.e. rocks, cosmic radiation).

In India, for example, (Ramsar Province) the background radiation dose corresponds to consuming 300 bananas per hour! This value is due to the composition of the rocks in the area.