Is our food poisoning us?

A few weeks ago, I saw that a Melbourne man had become famous around the world for poisoning himself. Accidental or deliberate poisonings are not that uncommon, but the method chosen by this man was seriously different. To prevent a cancer from coming back, he had chosen to take an apricot kernel extract supplement, as he believed this would help. Unfortunately apricot kernels contain the poison cyanide that can cause heart problems, hypoxia and death.

Apricot kernels contain cyanide, image from Flickr by natural.skincare.uae Shasha Spot Trading

Fortunately, the cause of his problems was identified swiftly and he received the appropriate treatment. However it got me thinking, I know that the leaves of rhubarb are poisonous and that one should avoid green potatoes, so what other of our favourite foods are actually dangerous?



Though not a chemical poison like cyanide, there are several foods that contain high levels of radioactive isotopes that could cause health issues. There were warnings issues around Japan and restrictions placed on fish sourced from areas exposed to the fallout from Fukushima. But ordinarily this isn’t naturally occurring. However bananas and brazil nuts do contain radiation.

Let’s start with bananas. Their radiation source comes from potassium-40, a radioactive isotope of potassium. However it is a small amount, with a kilo of bananas emitting 3500 picocuries of radiation. To put that in perspective, a person would need to eat 274 bananas a day for seven years to experience adverse events. So for all intents and purposes, bananas are safe.

Brazil nuts are much more radioactive, with a kilo containing 12 000 picocuries of radiation. It is the highest naturally occurring radiation content in food. In addition to radioactive potassium, it contains radium. A pocketful of brazil nuts are radioactive enough to set off reactor alarms at a nuclear power station.

Brazil Nuts- the most radioactive food. Source from Flickr by StainlessSteelRat.

Radioactive foods do exist, but their levels are so low that even for extreme consumption, it is unlikely there will be adverse effects.


Dangerous compounds:

Nutmeg and kidney beans can cause severe side effects. Nutmeg is used as a spice, and as such consumption is generally kept at fairly small amounts. However two tablespoons or more of nutmeg leads to hallucinogenic effects, nausea, vomiting and elevated heart rate. The main chemical culprit is myristicin, which can be found also in trace amounts in carrots. Though uncommon, poisonings are generally deliberate, with people seeking the potential hallucinogenic effects.

Kidney beans are a very common ingredient and it only takes four uncooked kidney beans to cause diarrhea, vomiting and nausea. The effect is caused by phytohemagglutinin. Most poisonings are from people using slow-cookers which does not elevate the temperature in the beans high enough for long enough to reduce toxin levels. Cooking at high temperatures for at least 10 mins, makes them safe to eat.


So what does this mean?

There are large numbers of foods that we consume constantly that contain potentially dangerous substances. But apart from kidney beans, the amount required is so large compared with typical consumption that it is unlikely any harm can occur accidentally. The danger arises when people begin to concentrate and take supplements containing these harmful substances just like the Melbourne man with apricot kernels.

8 Responses to “Is our food poisoning us?”

  1. Alasdair Browning says:

    I’d be interested to find out what foods are poisonous if eaten together, I haven’t heard of any like that.

  2. Alasdair Browning says:

    The radium and potassium come from the ground. It is in much higher levels in the brazil nuts as the tree has a very extensive root system. The tree absorbs more of the elements and concentrates it in the nuts. I too was very surprised by the kidney beans, apparently canned kidney beans avoid this problem. It seems to only occur with fresh ones.

  3. Alasdair Browning says:

    That’s really interesting Debbie, thank you. It certainly illustrates the difference between the dose to cause harm and the largest number that can actually be consumed. I feel that speed-eaters in general would be more likely to have a heart-attack, it definitely isn’t a healthy way to eat food!

  4. Alasdair Browning says:

    Thank you James. I definitely agree with the current environment of hearing that a food is toxic. It is certainly an area that can cause lots of hysteria.

  5. James Spyrou says:

    Great post Alasdair!

    Very fascinating stuff, I had no idea Brazil nuts were radioactive enough to set off a nuclear reactor alarm!

    “The dose makes the poison” is always a great thing to keep in mind whenever you hear something like “X is toxic”.

    This sort of honest communication about what makes foods safe or unsafe is the best way to combat misinformation.

  6. Debbie says:

    Side note: The world record number of bananas pealed and eaten in one minute is 8, set in 2012. The world record number of bananas eaten in one sitting is 30, set in 2014. Health authorities have banned further attempts as a contestant was sent to hospital after eating too many too quickly. But it wasn’t because they were poisoned, it was because they had a heart attack (which sparked panic because some people took that to mean eating bananas can give you a heart attack…)

  7. ke kang says:

    Great reading. Pesticides in food are also toxic, which have become an problem in some developing countries. Besides, some food are poisonous if eat together.

  8. Chris says:

    Thanks for the post Alasdair! I didn’t realize brazil nuts were radioactive, where does all the radium and potassium come from? Is it in the trees on which they grow or do they have some particular affinity to potassium and radium which allows them to absorb it? Also I was shocked to find that uncooked kidney beans were that bad for you!