Which pulses cause lathyrism when consumed on a regular basis?

January 1, 2026 •

4 min read

Outbreaks of lathyrism, a devastating neurodegenerative disorder, have affected tens of thousands of people during famines throughout history. Understanding which pulses cause lathyrism when consumed on a regular basis is critical for preventing this irreversible condition, particularly in regions where these hardy legumes are staple foods.

Quick Summary

Certain legumes from the Lathyrus genus, primarily grass pea (L. sativus), contain a neurotoxin that can cause lathyrism with prolonged, heavy consumption. The disease leads to irreversible spastic paraparesis, affecting motor neurons in the legs.

Key Points

Grass Pea (Kesari Dal): The pulse Lathyrus sativus is the main cause of neurolathyrism when consumed excessively and over time.
The Neurotoxin β-ODAP: A neurotoxic amino acid called β-ODAP is the compound in certain Lathyrus pulses that damages motor neurons.
Risk in Famine Conditions: Lathyrism outbreaks often occur during times of drought or famine when people rely heavily on the resilient grass pea as a primary food source.
Detoxification is Key: Soaking, rinsing, and cooking grass pea thoroughly can reduce its toxin content, but improper preparation is a risk factor.
Dietary Diversification: Limiting grass pea to less than 30% of the daily diet and mixing it with other cereals and pulses can significantly lower the risk of lathyrism.
Other Toxic Species: Lathyrus cicera and Lathyrus ochrus also contain β-ODAP and can cause lathyrism.
Irreversible Paralysis: Neurolathyrism causes irreversible spastic paraparesis, leading to permanent paralysis of the lower limbs.

The Primary Culprit: Lathyrus Sativus (Grass Pea)

The pulse most notoriously associated with causing lathyrism is the grass pea, scientifically known as Lathyrus sativus. Also referred to as kesari dal, chickling pea, or almorta, this legume is a crucial crop in parts of Asia and East Africa, thriving in harsh, drought-prone environments where other crops fail. However, its resilience comes with a significant health risk: the presence of a potent neurotoxin called β-N-oxalyl-L-α,β-diaminopropionic acid, or β-ODAP.

When grass pea constitutes a large proportion of a person's diet for extended periods, the β-ODAP accumulates in the body and damages motor neurons in the spinal cord. This is particularly problematic during times of famine and food scarcity, where reliance on this inexpensive and readily available crop increases dramatically. The neurotoxic effect is not immediate but builds over time, with symptoms appearing after months of consistent consumption.

The Mechanism of Neurolathyrism

The β-ODAP toxin acts as an excitotoxin, mimicking the neurotransmitter glutamate. This over-excitation of glutamate receptors leads to neuronal damage and eventual cell death, specifically targeting the upper motor neurons responsible for controlling lower limb movement. The resulting condition, neurolathyrism, is a form of spastic paraparesis characterized by stiffness, weakness, and paralysis of the legs. It's a non-progressive condition once consumption of the toxic pulse ceases, but the existing damage is typically irreversible.

Other Lathyrus Species That Can Cause Lathyrism

While Lathyrus sativus is the most common cause, several other species within the Lathyrus genus also contain the β-ODAP neurotoxin to varying degrees and can cause neurolathyrism if consumed in large quantities.

Lathyrus cicera (Flat-podded vetch): This species, like the grass pea, can also cause neurolathyrism.
Lathyrus ochrus (Cyprus vetch): Studies have shown that this pulse contains the ODAP toxin and is associated with neurolathyrism.
Lathyrus clymenum (Spanish vetchling): This species has also been implicated in causing neurolathyrism.

It is important to differentiate neurolathyrism from other types of lathyrism caused by different species and toxins. For example, the common ornamental sweet pea (Lathyrus odoratus) contains a different toxin, β-aminopropionitrile (BAPN), which causes osteolathyrism and affects bones and connective tissues, rather than the nervous system.

Factors Influencing Lathyrism Risk

Several factors determine the likelihood and severity of developing lathyrism from consuming toxic pulses:

Concentration of β-ODAP: The amount of neurotoxin in the legume can vary significantly based on environmental factors like drought stress, which can increase the toxin levels.
Cooking and Preparation Methods: Traditional processing techniques like soaking, rinsing, and parboiling can significantly reduce the β-ODAP content, with soaking for 12 hours potentially reducing it by 50-70%. However, in regions where resources like water and fuel are scarce during famines, these methods are often skipped.
Dietary Proportion: Lathyrism typically develops when grass pea constitutes a significant portion of the daily diet (over 30%) for an extended period (months). Mixing the pulse with other cereals or legumes can help dilute the toxin.
Individual Susceptibility: Factors such as genetics, age, gender, and nutritional status can influence an individual's vulnerability to the toxin. Younger males engaged in heavy physical labor, for instance, may be more susceptible.

Prevention and Mitigation Strategies

Given that the neurological damage from lathyrism is irreversible, prevention is the primary strategy. Public health campaigns focus on educating vulnerable populations about the risks associated with the overconsumption of Lathyrus pulses.

Comparison of Lathyrism Types


Feature	Neurolathyrism	Osteolathyrism	Angiolathyrism
Cause	Overconsumption of Lathyrus sativus and related species.	Consumption of Lathyrus odoratus (sweet pea).	Consumption of Lathyrus odoratus.
Toxin	β-ODAP (excitotoxin).	β-aminopropionitrile (BAPN).	β-aminopropionitrile (BAPN).
Primary Target	Motor neurons in the spinal cord.	Connective tissues, bones.	Connective tissues, blood vessels.
Symptoms	Spastic paraparesis, muscle weakness, rigidity, scissoring gait.	Skeletal deformities, bone pain.	Aortic aneurysms, cardiovascular issues.
Reversibility	Irreversible neurological damage.	May have lasting skeletal effects.	Often permanent damage.
Prevalence	Endemic in regions with drought and food insecurity.	Primarily documented in animals.	Primarily documented in animals.

Conclusion

The consumption of certain pulses from the Lathyrus genus, most notably the grass pea (Lathyrus sativus), is the direct cause of lathyrism when it forms a major part of the diet over prolonged periods. The underlying issue often stems from poverty and food insecurity, where people are forced to rely on this hardy but toxic crop. Awareness, dietary diversification, and proper detoxification methods are essential for mitigating the risk of this debilitating and largely irreversible condition. Continued efforts to develop low-toxin varieties of grass pea and support for alternative crops are crucial for protecting vulnerable communities. For more information on the agricultural context and risks associated with these pulses, authoritative sources provide deeper insights.

Visit the NIH website for further research on Lathyrism.

Frequently Asked Questions

No, lathyrism is not contagious. It is a toxic nutritional disorder caused by the consumption of neurotoxic pulses, not by a virus or bacteria.

Early symptoms often include muscle cramps, particularly in the calves, feelings of weakness or heaviness in the legs, and a dragging gait.

There is no known cure for the neurological damage caused by lathyrism. Management focuses on supportive care and preventing further exposure to the toxic pulses.

Risk can be reduced by avoiding excessive consumption of grass pea, diversifying one's diet with other food sources, and properly preparing the pulse through soaking and boiling to leach out the toxins.

No. Lathyrism develops from prolonged, heavy consumption, especially when the pulse is a staple food for several months. Occasional consumption in small amounts is generally not considered harmful.

Populations living in poverty-stricken, drought-prone regions who rely on grass pea as a primary food source are most at risk. Young adult males and those performing heavy physical labor may also be more susceptible.

Neurolathyrism is caused by β-ODAP from pulses like grass pea and affects the nervous system, leading to paralysis. Osteolathyrism is caused by a different toxin (BAPN) from sweet peas and affects bones and connective tissues.