 Other sources give a much higher oral LDLo (lowest published lethal dose) of 600 mg/kg.While the oxalic acid content of rhubarb leaves can vary, a typical value is about 0.5%, meaning a 65 kg adult would need to eat 4 to 8 kg (9 to 18 lbs) to obtain a lethal dose, depending on which lethal dose is assumed.Cooking the leaves with baking soda can make them more poisonous by producing soluble oxalates.