The original wild lettuce Lactuca serriola was known as “prickly lettuce” and grown for medicinal purposes as it contained a milky sap which has mild sleep-inducing properties. The soporific effects – and digestive benefits – meant the Romans served lettuce at the end of dinner; they were later served at the start of the meal, to get the digestion working. As new varieties were developed lettuce lost its sleep-inducing qualities, along with its bitter taste