Why does favism exist?
By Chelsie Vandaveer
October 14, 2003
Suggested Reading: Click here.
The fava bean (Vicia faba Linnaeus) is thought native to the eastern Mediterranean. The oldest known seeds, probably gathered from wild plants, were found in an archaeological dig near Nazareth and date from 6500 BCE. During the third millennium BCE, the cultivation of fava beans spread over the Middle East, North Africa, and central and southern Europe.
The consumption of fava beans causes favism (hemolytic anemia) in certain individuals of Mediterranean or African descent.
advertisement
Mediterranean Village, II by Lanny Barnard
|
|
|
Two alleles, variations of the Gd gene called GdMed and GdA-, on the X chromosome defines whether a person will have the disorder and to what degree.
Males, because they inherit only one X chromosome, have a much higher rate of favism. The anemia is caused when the red blood cells are destroyed by oxidation. According to anthropologist Jim Bindon, the Greeks described cases of favism over 2,000 years ago.
One in twelve cases is fatal. But fatal genetic mutations tend to be lost simply because the individual carrying the trait may not live long enough to pass it on. Theoretically, traits must give an organism an adaptive advantage or, at least, not be detrimental. Once medical science began to study the disorder and its history, it was curious that favism exists.
Doctors started to understand favism during the Korean Conflict when anti-malarial drugs caused anemia in some soldiers. Malaria, a parasitic infection of the blood, is spread by Anopheles mosquitoes. The cyclic malarial fever ensues when Plasmodium merozoites (parasites) are circulating in the bloodstream and invading the red blood cells. Merozoites are also damaged by oxidation.
During an anemic episode caused by favism, the damaged red blood cells cannot support the parasites and the oxidant level in the bloodstream is extremely high injuring more of the parasites. Merozoite development is reduced. Fewer merozoites survive, the malarial attack is lessened.
Favism is detrimental to the long term health of the individual, but not as detrimental as untreated malaria. It helped the individual survive malaria and live long enough to pass on the gene. Without malaria, the favism trait would not have survived in the population. Not surprisingly, the harvest and consumption of fava beans coincides with the peak of the Anopheles mosquito breeding season. ("Glucose-6-Phosphate Dehydrogenase (G6PD) and Malaria", Jim Bindon, PhD, Department of Anthropology, University of Alabama, 2002)
The Associazione Italiana Favismo - Deficit di G6PD has a wonderful website about favism. To learn more about this debilitating disorder, click on the link:
http://www.favism.org/favism/english/index.mv?pgid=myhome
Suggested Reading:
What is favism? Plants that Changed History - October 7, 2003
Why did ladies use bean poultices? Herbal Folklore - September 8, 2003
What is L-dopa? Plants that Changed History - September 2, 2003
What is a fava bean? Weird Plants - September 4, 2003
What was Jesuit Powder? Plants that Changed History - April 30, 2002
Who was José Celestino Mutis? Plants that Changed History - May 20, 2003
What is gin and tonic? What's in a Name? - May 23, 2003
Who smuggled quinine seeds for the British? Plants that Changed History - May 27, 2003
The Malaria Capers
More Tales of Parasites and People, Research and Reality
ecampus.com
by Robert S. Desowitz
Like such eminent science writers as Stephen Jay Gould and Lewis Thomas, Mr. Desowitz manages to make the basic principles of his subject immediately comprehensible to the general reader. He has also succeeded in giving us a profound appreciation of the ways in which scientific and medical knowledge advances, through hypothesis, error and experiment, through serendipity, dedication, and perseverance. [Tell me more...]
|
BACK TO TOP
