Margaret Lauterbach

Safety first when it comes to toxic beans

Margaret Lauterbach
Margaret Lauterbach

I recall being startled at seed vendor Jan Blum’s eating a Contender green snap bean raw, having just picked it in my garden. I’d never thought to eat a raw bean. Was I missing something?

Yes, I may have missed being poisoned. I’ve never cooked those snap beans longer than two minutes in a pressure cooker, and we’ve never gotten sick from eating them, but apparently it is possible to be poisoned by eating untreated beans.

Do not eat raw beans from your garden. Some or most contain naturally occurring toxic substances that can make us very sick. The degree of toxicity lies in the dose of anything — ingesting a large amount of any substance puts you at greater risk than if you ingest a tiny bit. If you have an unusual recipe for certain beans, follow that recipe exactly, using the variety of beans called for in the recipe. In the same vein, follow label instructions very precisely if you’re applying a pesticide or fertilizer in your garden. Some substances that were on the brink of being outlawed by previous EPA administrators have been given a green light by the new head of the EPA, so it’s up to the individual user to guard his or her safety.

Some or most beans contain a toxin called a lectin or phytohemagglutinin (PHA); its highest concentration is in red kidney beans. It’s high in white kidney beans (cannelini), too. Dry beans must be subjected to vigorous boiling for at least 20 minutes after soaking to destroy that toxic substance. Pressure cooking emulates that high temperature process, but pressure cooking carries its own risks if the beans foam and clog the vent while cooking. Lower-temperature cooking, such as in a slow cooker, doesn’t destroy the toxic effects, but instead increases them fivefold. To be completely safe, soak beans overnight, then replace the soaking water, boil vigorously for 20 minutes, and then turn down the temperature and simmer them as you usually would. That’s the advice from some experts and a woman online who had poisoned herself, her husband and guests with her “kitchen experiment.”

I confess I’ve never boiled dry beans for that long, and nobody has gotten sick on bean soup here, but I now will change my method. For bean soup, I usually assemble two cups of various varieties of home-grown dried beans, at least some of which may have high concentrations of that toxin, but I’ve been lucky.

Symptoms of phytohemagglutinin poisoning are nausea, vomiting and diarrhea, from mild to intense. Most beans, new and old world varieties, contain that toxin, although on the whole, dry beans are very nutritious for humans and easily grown and stored. I think these instructions to boil for 20 minutes would also apply to cooking dry or shelly beans, those that are shelled but still fresh and “green.”

Anytime you’re trying any new food, grown by you or not, try a little at first and wait to see if you have an allergic reaction to it. Almost any food is toxic in large amounts; even too much water can kill a human adult.

This phytohemagglutinin toxin is quite different from favism, a potentially fatal poisoning of a person who is intolerant of ingested fava beans. That intolerance occurs in some people of Mediterranean or African origin who have a G6PD (Glucose-6-phosphate dehydrogenase) genetic deficiency. A few thousand people die every year worldwide from that genetic problem caused by eating fava beans.

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We know our winter was a hard one, and even though we had an ample “blanket “ of snow, many rose shrubs in this valley were lost to winter kill. Anju Lucas, head of the perennials department at Edwards Greenhouse in Boise, said most of us who lost roses lost them to winter kill, not to the syringa bacterial cane blight we’ve had. She said rose wholesalers are listening to customers and giving retail outlets a broader range of choice for “own root” hybrid tea and floribunda roses. She said customers must understand that the “own root” roses do not grow as vigorously their first year as those that have been grafted onto Dr. Huey roots, and the leaves of “own root” roses are slightly smaller than those of grafted shrubs.

The big difference, though, lies in what happens after harsh winter kills the canes. Own root roses can come back, but the grafted roses will just send up Dr. Huey canes, necessitating replacement if you still want that certain cultivar. The Dr. Huey rose was introduced to market in 1914 and is a wichurana climbing rose now largely used for rootstock and breeding. It has single dark-red blossoms.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.