Detoxifying Desert's Manna

Article excerpt

Farmers need no longer fear the sweet pea's dryland cousin

For thousands of years, people dwelling in parched regions of the world, from northwest China to Ethiopia's highlands, have been cultivating a lovely flowering legume. The entire plant--stems and all--nourishes a host of domesticated animals. People roast the seeds for snacks, cook them into a protein-rich porridge or gravy, and grind them for baking into a hearty bread.

To families farming some of the poorest soils on Earth, this grass pea (Lathyrus sativus) would appear to be nothing less than "manna from heaven," observes Peter S. Spencer of the Oregon Health Sciences University in Portland. It thrives when and where other crops won't. Poor soil? No problem. Range lands undergoing a protracted drought? No problem. Torrential monsoon flooding? No problem.

Well, there is one problem, and it's serious, the neurotoxicologist points out. The grass pea produces an amino acid that can destroy a person's nerves.

During prolonged droughts, when alternative crops shrivel, people often make the grass pea a dietary staple. Yet when consumed in large quantities for just 2 or 3 months, the untreated seeds can trigger a disabling spasticity known as lathyrism. Unless affected people find other sources of food quickly, their condition could worsen, and they could eventually lose all use of their legs.

In the rural villages where lathyrism tends to occur, wheelchairs aren't available and they wouldn't easily traverse the terrain. In the worst cases, the victims can get around only by crawling. Moreover, Spencer points out, because men 18 to 40 years old have proved most vulnerable to lathyrism, affected communities tend to lose their breadwinners to this crippling, incurable nerve degeneration.

It was against this backdrop last month that Adel El-Beltagy announced that the International Center for Agricultural Research in the Dry Areas (ICARDA) in Aleppo, Syria, had succeeded in breeding virtually toxinfree cultivars of L. sativus. The accomplishment, which took some 15 years and cost more than $1 million, has produced strains offering the yield, taste, and environmental ruggedness of the original plant.

Says EI-Beltagy, the institute's director general, ICARDA's breeders transformed poor farmers' potentially devastating "option of last resort" into a safe alternative.

And none too soon, lathyrism epidemiologists contend. In Gojam, Ethiopia, for instance, "the [cumulative] prevalence of spastic paraparesis [lathyrism] is 7.5 per 1,000 individuals--which is unbelievable for a neurodegenerative disease," Spencer notes.

Fernand Lambein of the University of Ghent in Belgium and his colleagues described a new lathyrism epidemic in northwestern Ethiopia's Wello area in the July 24, 1999 LANCET. Crippling at least 2,000 people, it was triggered by the drought of 1995 and 1996, which wiped out nearly all local crops other than the grass pea. This episode proved so serious that nearly one in five affected individuals was left "a crawler," the researchers noted--meaning the victim lost all ability to walk. That's at least four times the proportion of such severely affected cases that normally occur.

Droughts in Bangladesh during the early 1970s triggered an even more dramatic plague of lathyrism that disabled up to 70,000 of its victims, according to neurologist Anisul Haque of the Bangabandhu Sheikh Mujib Medical University in Dhaka. The outbreak, which he notes left some of these individuals quadriplegic, hit a few regions unusually hard, permanently disabling 20 out of every 1,000 inhabitants.

Among people eating the same amount of toxic grass-pea seeds, only a few typically develop the disease, Lambein has found. His data hint that dietary factors, such as deficiencies in trace minerals, might foster human vulnerability to the pea's toxin. Livestock rarely show poisoning symptoms. …