Bean

• 1. Introduction

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  Four or five raw red kidney beans can leave a person doubled over with stomachache, vomiting, and diarrhea. The culprit is a flavourless toxin called phytohaemagglutinin, a lectin that only cooking can destroy. Stranger still, under-cooked beans may be more toxic than raw ones, and slow cooking can soften a bean without making it safe. This is the hidden double life of the bean, a seed humans have eaten since the seventh millennium BCE yet still mishandle. A bean is the seed of plants in many genera of the legume family, Fabaceae, grown as food for people and animals. How did a food long dismissed as fare for the poor become a crop produced in the millions of tons? And why do so many cultures keep their own remedy for the gas it causes?

• 2. A Word Older Than The Bean

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  The word "bean" has been in common use in West Germanic languages since before the 12th century, with cognates such as the German Bohne. Back then it named broad beans, chickpeas, and other pod-borne seeds, long before Europe knew the New World genus Phaseolus. The Columbian exchange of plants between Europe and the Americas stretched the word further. It came to cover Phaseolus seeds like the common bean and the runner bean, and the related genus Vigna. People applied "bean" loosely to anything of similar form, including Old World soybeans and lupins. The label even jumped to the fruits or seeds of wholly unrelated plants, such as coffee beans and vanilla beans, neither of which is a legume at all.

• 3. Seeds With The Dead

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  Beans in an early cultivated form were grown in Thailand from the early seventh millennium BCE, predating ceramics. In ancient Egypt, beans were deposited with the dead, a quiet sign of their value. Not until the second millennium BCE did large-seeded broad beans appear in the Aegean, Iberia, and transalpine Europe. The Iliad, written in the 8th century BCE, gives beans and chickpeas a passing mention, cast on the threshing floor. Across the Atlantic, the oldest-known domesticated beans in the Americas were found in Guitarrero Cave, Peru, dated to around the second millennium BCE. Genetic analysis of the common bean, Phaseolus, shows it originated in Mesoamerica before spreading southward. The first European to encounter Phaseolus was Christopher Columbus, who saw them growing in fields while exploring what may have been the Bahamas.

• 4. Many Genera, One Name

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  Phaseolus alone, native to the Americas, gives the world kidney, pinto, navy, black, and Borlotti beans, plus lima beans, runner beans, and the tepary. Pre-Columbian peoples domesticated five kinds of Phaseolus, selecting pods that did not open and scatter their seeds when ripe. Vigna, mostly from South Asia, supplies the mung bean, urad bean, yardlong bean, black-eyed peas, moth bean, and adzuki beans. Other genera carry their own surprises in their chemistry. Mucuna pruriens, the velvet bean of tropical Asia and Africa, contains L-DOPA and can cause itching and rashes on contact. Vicia faba, the broad bean, causes favism in susceptible people. The biodiversity of all these cultivars is now threatened by modern plant breeding, which favours a few high-yielding varieties. As of 2023, the Norwegian Svalbard Global Seed Vault held more than 40,000 accessions of Phaseolus species.

• 5. The Three Sisters

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  Pre-Columbian peoples as far north as the Atlantic seaboard grew beans in the "Three Sisters" method of companion planting, interplanting them with maize and squash. The tall corn stalks acted as support for the climbing beans. As legumes, the plants fix nitrogen and so need less fertiliser than most crops. They form seeds with a high protein content, most dry beans running 21 to 25% protein by weight, with dry soybeans reaching 36.5%. Most beans are summer crops needing warm temperatures, with peas as the exception. Maturity typically takes 55 to 60 days from planting to harvest, the pods turning yellow and drying as the beans inside change from green to their mature colour. Many beans are vines that need poles or bean cages. More recently the commercial bush bean was developed, which needs no support and produces all its pods at once. Beans were cultivated across Chile in Pre-Hispanic times, likely as far south as the Chiloé Archipelago.

• 6. Millions Of Tons

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  India is the world's largest producer of pulses, accounting for 17.56 million metric tons in 2016, or 21.47% of a world total of 81.80 million tons. Canada and Myanmar followed, with Tanzania the most important producer in Africa. The Food and Agriculture Organization sorts legume data into three categories: dry pulses, oil crops covering soybeans and groundnuts, and fresh vegetables. The numbers reveal an uneven boom. Total dry pulses only doubled between 1961 and 2016, while population grew 2.4 times, so per capita production actually fell. Soybeans tell a different story, rising more than twelvefold from 26.88 million tons in 1961 to 334.89 million in 2016, driven by animal feed and oil. For dry beans of the genus Phaseolus, India again leads, followed by Myanmar and Brazil, out of a 2020 world total of 27,545,942 tonnes.

• 7. The Toxin And The Gas

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  Red kidney beans are particularly toxic, and the cure is simple: boil them for at least ten minutes. The risk does not apply to canned beans, which are already cooked. One reported poisoning came from butter beans used to make falafel, soaked and ground without boiling, shaped into patties, and shallow fried. Bean poisoning is not well known in the medical community, and many cases may be misdiagnosed or never reported. Beyond toxins, beans carry antinutrients. Phytic acid interferes with bone growth and interrupts vitamin D metabolism. The famous flatulence comes from oligosaccharides like raffinose and stachyose, which the human gut cannot break down. Bacteria in the large intestine digest them instead, producing gases such as methane. Cultures answer this in their own ways: Mexico uses epazote, India asafoetida, Germany savory, the Middle East cumin, and Japan the seaweed kombu. Beansprouts pose a separate danger, with many outbreaks of salmonella, listeria, and Escherichia coli traced to sprouts that were not thoroughly cooked.

• 8. Food Of The Poor

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  Farmers ate grains and vegetables and got their protein from beans, while wealthier classes could afford meat, which is why beans were long seen as a food of the poor. Ken Albala describes a "class-based antagonism" toward beans in European society. The flatulence is so well established that it became the theme of a children's song, "Beans, Beans, the Musical Fruit." A studied remedy does exist: alpha-galactosidase, an enzyme extracted from the mould fungus Aspergillus niger, which breaks down glycolipids and glycoproteins. The bean's oddest cultural turn belongs to the Mexican jumping bean. It is a segment of seed pod occupied by the larva of the moth Cydia saltitans, sold as a novelty, and it jumps when warmed in the palm of the hand. Scientists suggest the resulting random walk may help the larva find shade and survive a hot day.