Khesari Dal: The Main Culprit Behind Neurolathyrism
Lathyrism, specifically neurolathyrism, is a neurodegenerative disorder that has historically affected impoverished populations in regions prone to drought, particularly in India, Bangladesh, and Ethiopia. The legume responsible for this condition is Lathyrus sativus, commonly known as khesari dal or grass pea. While most people can consume this legume in small, mixed quantities without harm, the risk arises when it becomes a staple, making up a significant portion of the diet over an extended period.
The Neurotoxic Compound: β-ODAP
The toxicity of khesari dal is attributed to a naturally occurring neurotoxic amino acid called β-N-oxalyl-L-α,β-diaminopropionic acid, or β-ODAP. This compound acts as an excitotoxin, mimicking the neurotransmitter glutamate and overstimulating the nerve cells in the brain and spinal cord. This excessive excitation leads to neuronal damage and death, specifically affecting the upper motor neurons responsible for voluntary movement in the lower limbs. The neurological damage is often irreversible, manifesting as progressive and permanent paralysis.
How Lathyrism Develops
Developing lathyrism requires both a high intake and a prolonged duration of khesari dal consumption. The disease is often linked with food insecurity and famine, as the grass pea is a hardy and drought-resistant crop that can thrive when others fail. During such times, people may rely on khesari dal as their primary or sole source of protein, leading to the gradual accumulation of the β-ODAP toxin in their bodies. Poor nutritional status can also increase a person's susceptibility to the toxin.
Symptoms and Prevention of Neurolathyrism
The symptoms of neurolathyrism often begin subtly and progress over time. Initial signs may include muscle cramps and a sensation of weakness or heaviness in the legs. As the condition advances, more severe symptoms like muscle stiffness, an exaggerated reflex response (hyperreflexia), and a characteristic scissor-gait walking pattern can develop. The damage is typically confined to the lower limbs, leaving upper body strength and sensation unaffected.
Prevention is the most crucial aspect of managing lathyrism, as there is no cure once the paralysis has set in. Public health measures and dietary education are key to reducing its incidence.
Preventative Strategies:
- Dietary Diversification: The most effective method is to ensure khesari dal constitutes less than 30% of the total daily caloric intake, mixing it with other cereals and pulses.
- Improved Preparation Methods: Simple cooking techniques can significantly reduce the β-ODAP content. Soaking the dal for at least 12 hours, discarding the water, and then rinsing thoroughly can reduce the toxin by 50-70%. Parboiling the legume and discarding the water is another effective method.
- Low-Toxin Varieties: Agricultural research has focused on developing and promoting low-toxin varieties of Lathyrus sativus to mitigate health risks while preserving the crop's hardiness.
- Public Awareness Campaigns: Educating communities on the risks of overconsumption and the proper preparation techniques is essential.
Comparison: Khesari Dal vs. Other Legumes
| Feature | Khesari Dal (Lathyrus sativus) | Other Common Dals (e.g., Arhar, Moong) |
|---|---|---|
| Toxin Presence | Contains the neurotoxin β-ODAP, particularly when grown in harsh conditions. | Generally considered safe for consumption and does not contain β-ODAP. |
| Hardiness | Extremely drought-resistant and can thrive in poor soil. | Less tolerant of extreme drought and requires more favorable growing conditions. |
| Primary Risk | High risk of neurolathyrism if consumed excessively and chronically as a staple food. | No risk of neurolathyrism with normal consumption. |
| Nutritional Profile | A good source of protein, especially the amino acid lysine. | Excellent sources of protein, dietary fiber, and various vitamins and minerals. |
| Historical Use | Often used as a famine food, when other crops have failed. | Widely consumed as a regular part of diverse diets. |
| Cultivation Status | Historically banned in parts of India due to health risks, though recent studies have re-evaluated its safety under normal consumption and improved genetic strains. | Continues to be a key part of agricultural production and diet. |
Conclusion
The question of which dal is responsible for lathyrism is answered definitively by identifying khesari dal (Lathyrus sativus). The disease is a direct result of prolonged and excessive consumption of this legume, allowing the neurotoxin β-ODAP to accumulate and cause irreversible neurological damage. The condition is a socio-economic issue, emerging predominantly in famine-stricken areas where khesari dal's hardiness makes it a survival food. With improved agricultural practices, the development of low-toxin varieties, and public education on proper food preparation, the incidence of neurolathyrism has significantly declined. Addressing lathyrism involves a dual strategy: reducing dependence on this single crop through dietary diversification and mitigating the risk of exposure by teaching safe preparation methods. Ultimately, while khesari dal can be a nutritional resource, its consumption must be managed carefully to prevent the devastating effects of lathyrism.
Authoritative Source
For additional scientific information on the health implications and future of Lathyrus sativus and neurolathyrism, refer to this review article published by the National Institutes of Health: Lessons from neurolathyrism: a disease of the past & the future of Lathyrus sativus (Khesari dal).
