The seeds contain a neurotoxin that causes lathyrism, a neurodegenerative disease, if eaten as a primary protein source for a prolonged period.

[4] The disease has historically occurred after famines in Europe (France, Spain, Germany), North Africa, and South Asia, and is still prevalent in Eritrea, Ethiopia, and Afghanistan (panhandle) when Lathyrus seed is the exclusive or main source of nutrients for extended periods.

ODAP concentration increases in plants grown under stressful conditions, compounding the problem.The crop is harmless to humans in small quantities, but eating it as a major part of the diet over a three-month period can cause permanent paralysis below the knees in adults and brain damage in children, a disorder known as lathyrism.

(Kew Gardens)[4]Some authors have argued that this toxicity is overstated, and L. sativus is harmless as part of a normal diet.

It depicts a woman who can no longer walk due to lathyrism, surrounded by starving people waiting for bowls of grass pea-based food.

L-ODAP is reported to act as an activator of calcium-dependent protein kinase C.[needs context] Breeding programs are underway to produce lines of Lathyrus sativus that contain ODAP levels too low to be dangerous, while maintaining disease and insect resistance and tolerance to drought, heat, and salinity.

From 2016 to 2018, the International Center for Agricultural Research in the Dry Areas (ICARDA) evaluated wild relatives[21] to explore genes for low or no ODAP and resistance/tolerance to biotic/abiotic stresses and transfer them to cultivated grass pea.