Weaning is the process of replacing breast milk with other food. The infant is fully weaned after the replacement is complete. Most mammals stop producing the enzymelactase at the end of weaning, and become lactose intolerant. Figures vary, but worldwide, humans lose about 75 to 95 percent of birth lactase levels by early childhood, and lactase continues to decline with age. However, the prevalence varies widely among ethnic backgrounds. Estimates range from 2 to 5 percent in those with Northern European ancestry to nearly 100 percent in adult Asians and American Indians. Africans and Ashkenazi Jews have prevalences of 60 to 80 percent, while Latinos have a prevalence of 50 to 80 percent. Psychological factors affect the weaning process for both mother and infant, as issues of closeness and separation are very prominent.
In the past bromocriptine was in some countries frequently used to reduce the common engorgement experienced during weaning. This is now done only in exceptional cases due to frequent side effects and slight benefits. Other medications such as cabergoline, lisuride or birth control pills may occasionally be used to suppress lactation.