Flowering Runner bean

This question seems to be very common all over the web. In fact only a few months ago I researched the exact same topic after realising I couldn’t possibly use up all my garden produce. I had grown some runner beans (Phaseolus coccineus), which in the UK at least are grown for their green (young) pods, not the beans inside. In fact, once the beans inside develop, the green pods become tough and stringy and not very nice to eat at all.

But what if you’re well and truly sick of runner beans with almost every meal, and you want to just leave them on the plant to grow larger and store the beans inside for winter meals…

CAN I EAT THE MATURE BEANS INSIDE RUNNER BEANS?

Turns out, yes you can. Even though they’re different from the red ones you get in cans, mature runner beans are called kidney beans due to their shape. They come in fantastic colours and would look very attractive in salads etc. BUT: you CANNOT eat them raw!

Dried runner beans

I HEARD THAT MATURE RUNNER BEANS ARE TOXIC?

Indeed they are, many beans are toxic to some extent. You are NOT supposed to eat them raw, especially not in large quantities. Of course many people grew up stealing a few raw bean pods from the garden or allotment and enjoying the crunchy and fresh taste without getting ill, but this is not recommended. Runner beans contain the toxin Phytohaemagglutinin which can produce very harmful effects in sufficient quantities (for red kidney beans, as little as 4 beans can cause poisoning). Symptoms include nausea, vomiting and diarrhoea. Depending on the quantity eaten, the symptoms may pass once the stomach contents are emptied, or medical treatment may be necessary due to excessive loss of fluids.

SO, IF THEY’RE TOXIC, HOW DO I PREPARE THEM?

But don’t let the above information discourage you! The toxin Phytohaemagglutinin is easily broken down by boiling so all you need to ensure is that your mature kidney beans are boiled for AT LEAST 10 minutes prior to consumption. I prepared fresh beans that I had just shelled and 10 minutes left them a bit too crunchy anyway so chances are you’d want to cook them a bit longer.

Bear in mind that BOILING temperatures are needed ( this means above 100 degrees Celsius). Sticking the beans in a slow cooker that operates at a lower temperature will NOT help and is likely to make the beans more harmful. If you intend to slow cook a meal containing fresh or dried kidney beans, always boil them properly for a minimum of 10 minutes beforehand and then transfer them to the slow cooker.

BUT I HARDLY EVER COOK GREEN BEANS FOR 10 MINUTES OR MORE! AND I’VE NEVER GOTTEN SICK!

This may be so, not everyone is equally sensitive to the toxin contained in these beans. And the majority of the toxin is contained within the beans inside the pods. If you eat the green beans before the seeds inside have matured, they may be perfectly safe with less cooking and in some cases even raw. Follow common sense and culinary tradition, but when in doubt just boil them a bit before use to be safe!