In China there was a longstanding practice of using nightsoil (i.e. human feces) as fertilizer. The health risks are great and doing it safely requires strictes

In China there was a longstanding practice of using nightsoil (i.e. human feces) as fertilizer. The health risks are great and doing it safely requires strictest adherence to hygiene protocols. Everything is boiled for safety, even lettuce is wilted in the pan. It's no surprise that ice water gets you the crazy look. Food taboos oftentimes make sense. Sometime ago someone mentioned traditional, cyanogen-rich varieties of cassava, which are pest-resistant but require boiling for hours in an open pot. If you omit that you end up with motor neuron disease, konzo as they call it, but only after several years. So it's not surprising that superstitions sprang up around the plant, some of which are actually protective.