Complementary feeding, which embraces all solid and liquid foods other than breast milk or infant formula, is strongly influenced by cultural, familial and economic factors. For many times, there was a strong taboo on the use of colostrum ("the white blood") during the first week after delivery, sometimes even the first month. Therefore, the newborn baby received complementary foods as gruel, or panada. However, in the Greek civilization, wet nurses were asked by contract to breastfeed exclusively for the first 6 months and to start complementary feeding thereafter. From the sixteenth century onwards, many writers deplored the practice of giving gruel and panada during the first six months before the teeth erupted. In 1921, a Swedish pediatrician, Jundell, reported for the first time that starting complementary feeding at 6 months of age was associated with a better growth and resistance to infections. The recommendation of the World Health Organization to start complementary feeding after a 6-month period of exclusive breastfeeding is often in contradiction with the habits of the populations to propose very early other food sources than breast milk.