Pythagoras forbade his followers to eat fava beans. Beyond the political implica
ID: 20466 • Letter: P
Question
Pythagoras forbade his followers to eat fava beans. Beyond the political implications (Greeks voted with beans), there turns out to be a rational basis for this proscription. In the Middle East, defective forms of the gene encoding glucose-6-phosphate dehydrogenase (G6PD) are common. These mutant forms of the gene typically reduce G6PD activity to about 10% of normal. They have been selected for in theMiddle East, and in other areas of the world where malaria is common, because they afford protection against the malarial parasite. G6PD controls the first step in the pathway for NADPH production. A lower-than-normal level of NADPH in red blood cells creates an environmental unfavorable for growth of the protest Plasmodium falciparum, which causes malaria.
Although somewhat protected against malaria, G6PD-deficient individuals occasionally have other problems. NADPH is the principal agent required to keep the red cell cytosol in a properly reduced state, constantly converting transient disulfide bonds (-S-S-) back to sulphydryls (-SH HS-). When a G6PD-deficient individual eats raw orundercooked fava beans, an oxidizing substance in the beans overwhelms the reducing capacity of the red cells, leading to a severe – sometimes life-thretening –
hemolytic anemia. How do you suppose eating fava beans leads to anemia?
Explanation / Answer
Favism is a medical condition which is caused by an enzyme deficiency in the blood. People with this deficiency can experience anemia as a result of exposure to fava beans. The condition is most common in people who live around the Mediterranean, and it generally affects men, although women can be carriers. For people with this deficiency, an assortment of other foods and some pharmaceuticals can also trigger a reaction. The most effective treatment is avoidance of substances which can trigger anemia, and a blood transfusion for people in anemic crisis. Officially, favism is known as Glucose-6-Phosphate Dehydrogenase Deficiency, or G6PD. The severity of this condition varies from patient to patient; in all cases, people suffer what is known as hemolytic anemia because their lack of this enzyme means that the health of their red blood cells is impaired. As a result, the cells can break down very quickly, triggering a range of symptoms from tiredness to coma, depending on the severity of the anemia. Southeast Asians and some Africans are also at risk of favism. Fava beans have been linked with anemic conditions since ancient times, which is why “favism” is used as a generic name for G6PD deficiency. However, not all people with this condition react to fava beans, and other legumes can also spark an anemic episode. G6PD deficiency also causes severe reactions with some medications; people with this condition should talk to their doctors, as different drugs represent different risks for unique individuals, and the list of risky drugs is quite long. For someone with severe favism, exposure to the pollen of fava beans can cause a reaction, as will consumption of the beans. The patient may feel tired, feverish, or experience a headache, and the condition can also cause abdominal pain, nausea, and vomiting. If left untreated, favism can result in serious health problems, like a coma. Early warning signs of favism include jaundice, dark urine, and a general sense of feeling run down and tired all the time. People who think that they may have favism can be tested for it. There is a simple blood test which will check a patient's enzyme levels to determine whether or not the patient has favism and how severe the condition is. If anyone in your family has the condition, you may want to consider testing, since G6PD is genetic. +++++ Favism (G6PD deficiency). Favism is an inherited disease in which a person lacks an enzyme called glucose-6-phosphate dehydrogenase (G6PD). When these people eat fava beans, they develop a condition called hemolytic anemia. This anemia causes red blood cells to break apart and block blood vessels. When such blockage occurs in the kidneys, it can result in kidney failure and even death. Although favism is usually detected in childhood, adults can be affected as well. G6PD deficiency is rare, occurring mostly among people of Mediterranean, African, and Southeast Asian descent, but others can be affected as well. Your physician can perform a blood test for G6PD to determine whether you are at risk. If you find you have inherited G6PD deficiency, your dietitian can help you locate other foods that may be of concern, and can help you plan safe and healthful menus. +++++ When an individual with a G6PD deficiency is exposed to fava beans or pollen, the red blood cells are attacked and are no longer able to carry oxygen to the cells. This is called hemolytic anemia. Symptoms of a hemolytic attack include dark orange urine; a yellowing of the mucous membranes and skin; a rapid increase in body temperature; fatigue; rapid breathing; and rapid, weak pulse. Transfusions may help, as may dialysis, if acute renal failure ensues. A physician should be consulted for treatment options.
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