Know your beans

Posted by Andrew Wadge on September 16th 2008 in Science, safety and health

Today’s Independent contains an interesting article which serves as a cautionary tale to all of us. The article tells the tale of an unfortunate family who suffered a nasty dose of food poisoning as a result of eating dried beans that weren’t cooked properly.

Beans contain natural toxins called lectins (also known as phytohaemagglutinins) and other harmful compounds called protease inhibitors. The highest concentrations are found in kidney beans, especially red kidney beans. Protease inhibitors reduce the digestibility of protein, and lectins severely inhibit absorption of nutrients by the body. As few as four or five raw beans can cause severe stomachache, vomiting and diarrhoea – these very nasty symptoms are exactly what Vicky Jones and her family suffered, leading to an ambulance being called out and the poisons unit being contacted.  Thankfully all three of them made a full recovery overnight but this tale of misadventure should remind us all that cooking instructions, like use-by dates, are there for a reason and are to be ignored at our peril.

The Agency’s eatwell website is a really useful place to go for information about all things foody – including how to cook beans and pulses properly. If only Vicky had discovered this while she was planning her menu.

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Yes ...

Posted by Andrew Wadge on 20/10/2008 - 17:14

The short answer is yes, mung bean sprouts are safe to eat raw and can contribute to your five portions of fruit and veg a day. A slightly longer answer is that a wide range of beans can be sprouted, the most common one being the mung (garden) bean, often sold as 'Chinese bean sprouts'. Although both mung beans and their sprouts do contain lectins, they are at much lower levels than found in kidney beans, and are not of any health concern. Mung bean sprouts are safe to eat raw. Blanching alone would not be sufficient to destroy lectins so it is possible that the instruction was for cooking or for hygiene purposes.

Alfalfa sprouts contain a naturally produced toxin called canavanine. Canavanine is present in all parts of the plant (leaves, stem and seeds), with the highest concentration present in the seeds. The seeds and sprouts of alfalfa have been reported to induce a systemic lupus erythematosus (SLE) like syndrome in animal studies and canavanine has been implicated in reactivation of SLE in humans who ingested alfalfa tablets. However, in a more recent study there was no link between alfalfa consumption and development of SLE. In view of the limited data, patients with systemic lupus erythematosus (SLE) may wish to avoid alfalfa seeds and sprouts as a precaution, but for others they are ok.

With other sprouted beans, do check whether they are intended to be eated raw if you are unsure and, as always, be careful about food hygiene.

Raw beans

Posted by Tanya May (not verified) on 18/09/2008 - 09:11

Can anyone confirm whether it is safe to eat raw (mung)beansprouts, or other types of sprouted beans? A few years ago, pack instructions used to say words to the effect that they should be "blanched in boiling water" before use, but these instructions no longer seem to appear. Sprouted beans are delicious in salads and sandwiches and hopefully the sprouting process eliminates the toxins - does it?