Kangkong, A Veggie Which Can Cause Leg Cramp When Excessively Consumed?

Sambal Kangkong (马来风光), one of the signature Asian dishes you can easily find, especially in Singapore where this is one standard dish to have in a Zi Char stall. But have you ever heard this from your folks before? Don't eat so much kangkong, otherwise you will suffer leg cramps at night! Well, I do....