The Mystery Bean


Avoid fava beans.



What would a Greek philosopher in the 6th century BC have against one of the most common vegetables of his area and time? This has been the subject of debate almost from the moment Pythagoras completed the sentence. An incredible assortment of explanations has been offered, ranging from reincarnation to sexual symbolism.

Only relatively recently have scientists begun to think that Pythagoras may have been on to something. For some people, we now know, fresh fava beans can be poisonous. This fairly common genetically transmitted condition--called, appropriately, favism--was recognized only at the turn of this century and has been explained fully just in the last decade.

The condition is especially prevalent in the old Magna Graecia--the region ruled by the ancient Greeks--where as much as 30% of the population in some areas has it.


Whether the poisonings were the basis of Pythagoras’ pronouncement or not, no one can say for certain. While today’s cults seem determined to tell all about their religious beliefs, the Pythagoreans were notoriously close-mouthed.

Iamblichus tells of the time a group of Pythagoreans were being pursued by their enemies when they came across a field of favas in bloom. Rather than disobey the master’s dictates and flee through the field, they were slaughtered. And when two who were captured were questioned about their beliefs, they refused to answer. The husband chose death and the wife, a Spartan, bit off her tongue and spit it at her captors to avoid spilling the beans.

As Mirko Grmek so pithily puts it in her book, “Diseases in the Greek World” (Johns Hopkins, 1991), “The Pythagorean rule of silence explains why the persons in antiquity who dared write on this subject were already in the dark.” Of course, that didn’t stop them from writing.

The state of the debate was pretty well summed up by Aristotle, who says that Pythagoras proscribed fava beans “either because they have the shape of testicles, or because they resemble the gates of hell, for they alone have no hinges, or again because they spoil, or because they resemble the nature of the universe, or because of oligarchy, for they are used for drawing lots.”

And if you can’t find something there you like, there’s more. Diogenes proposed that the Pythagoreans rejected favas because they cause thought-disturbing flatulence, saying, “One should abstain from fava beans, since they are full of wind and take part in the soul, and if one abstains from them one’s stomach will be less noisy and one’s dreams will be less oppressive and calmer.”

Despite this injunction, it should be noted that fava beans are lower in indigestible sugars--and in fiber--than many other beans. It’s just that until the discovery of the Americas, they were the sole representative of beandom in Europe.


The later sect known as the Orphics believed that Pythagoras had forbidden the eating of favas because they contain the souls of the dead. “Eating fava beans and gnawing on the heads of one’s parents are one and the same,” went one of their sayings.

Since the Renaissance, scholars have proposed even more solutions. “Humanistic scholarship, with free association as its main guide, has offered explanations that range from the mildly ridiculous to the extremely ridiculous,” wrote Robert Brumbaugh and Jessica Schwartz in a 1980 issue of the journal Classical World.

Be that as it may, the modern explanation is even more interesting. Around the turn of the century, physicians began to recognize that after eating fresh fava beans, some people began to suffer a sudden illness that, in some cases, led rapidly to death. The cause seems obvious today, but remember that it wasn’t until 1904 that Clemens von Pirquet came up with the medical definition for allergies. Before that, it was difficult for scientists to get a handle on the concept that what might be fine for one person might be poison for another.

When scientists began to investigate favism, they found a genetically transmitted deficiency in a certain blood enzyme--glucose-6-phosphate dehydrogenase (called, for obvious reasons, G6PD). In about 20% of the people with this deficiency, eating fresh fava beans can trigger a severe hemolytic anemia. Sufferers exhibit symptoms of jaundice and anemia and excrete blood in their urine. Even today, death follows for almost 10% of those who suffer this reaction, usually within a matter of days.

The condition is most common in males, by a ratio of almost 3 to 1. Only women who carry the gene from both sides of the family are susceptible. And it is most severe among infants and children; the poison can be passed in mother’s milk.

We now know that there are three distinct genetic strains of G6PD deficiency. One is centered in the Greek plains, Southern Italy and the islands of the Aegean. That’s precisely the area controlled by the ancient Greeks. Crotona, where Pythagoras had his settlement in the modern-day state of Calabria, is one such concentration.


Another genetic type is centered in the Mediterranean coast of Africa, particularly Egypt and Morocco. The third is in Central Asia, extending into China--which is perplexing, because the fava bean has no long history there. However, one incident of favism reported in Southern California involved a young Chinese boy who had eaten yewdow--a snack food made from fried and salted fava beans.

Although the initial medical question was answered, a more interesting evolutionary issue had been raised: Why would people continue to consume fava beans in an area where a relatively high percentage of them would get sick from eating them? Logically, one would assume that either people would stop eating fava beans or--deprived of a prime foodstuff--people carrying the genetic trait would eventually die off. Yet after more than 3,000 years of fava-eating, neither has happened.

A possible explanation began to appear in the 1920s, when scientists found that G6PD deficiency is actually a defense against malaria, historically a major health problem in Greece and Southern Italy. It occurred so often that it was accepted almost as a matter of course (much as we live with the flu). As recently as 1943, 100,000 cases of malaria were reported in one year on the island of Sardinia. The G6PD deficiency, scientists found, helps defend against malaria parasites by reducing the amount of oxygen in red blood cells.

Things became even more interesting during World War II, when doctors treating malaria with quinine-based drugs noticed that many people with favism reacted to the medicine in the same way they did to eating fava beans.

On further investigation, scientists found that fava beans contain several chemical compounds that resemble those found in quinine-based drugs. After decades of research, in the last few years they have proven that fava beans themselves also fight malaria, and in much the same way as G6PD deficiency: by reducing the amount of oxygen in the blood.

Thus, it is now theorized that what keeps the scales in balance in this evolutionary standoff is that when fava beans are consumed by people with G6PD deficiency who don’t suffer from favism (the vast majority, remember), the resistance to malaria is raised even further.


Therefore, even if favas are dangerous to a certain percentage of people, their benefits to the remainder of the population far outweigh their shortcomings.

Is this the secret behind Pythagoras’ puzzle? It’s hard to say, 26 centuries later. One thing’s for certain: He’s not talking.

* Soup bowl and plate from Bristol Kitchens, South Pasadena.