During ancient timings ladies boil leaves of chenopodium (bathua), palak before using in cooking dishes.Thats contain scientific logical reason.But they not inform properly to the next generation due to the lacking of conversion. They use and understand these reasons by their local language or different words.
(1)Consuming bathua also reduces the level of calcium in the body. Actually, this is because oxalic acid is present in this vegetable, which can reduce the amount of calcium in the body. People suffering from skin allergies should also avoid consuming bathua.When heated, oxalic acid first boils off water of hydration, then sublimes, and finally decomposes:Oxalic acid crystals are nothing but dehydrated oxalic acid (H2C2O4. 2H2O). On heating, the water of crystallization is lost first. Then, the ✅dehydrated oxalic acid decomposes into carbon dioxide (CO2), carbon monoxide (CO) and water(H2O).
(2)Another benefits of boiling vegetables are - Like carrots , boiling increase Vit A. and its absorption because vit A is not water soluble.
(3)Boiling break undigestible cellulose walls of vegetables this helps to absorb nutrients easily by the body .
Mostly people not using the residual water of boiling these vegetables because they think that recipe may lose its better taste .