NEWS: Low Vitamin D Linked to Schizophrenia
"During the Renaissance, a common opinion prescribed that children were not to be weaned before the second year of life; for this reason, among the elite classes, wet nursing was a very widespread practice," the researchers wrote.
Indeed, the Medici princes were never weaned until they were at least 2; starting from eight to nine months, woman's milk was integrated with paps made of soft bread and apples. Cereals and breast milk are known to supply little vitamin D, while fruit contains none.
"With prolonged breast-feeding, vitamin D deficiency is highly expected to rise, in particular if the other main risk factor, inadequate sunlight exposition, is associated with a diet based on maternal milk," the researchers said.
They added that two hours per week is the required minimum period of exposure to sunlight for infants if only the face is exposed - something the Medici children did not enjoy.
At that time, skin color was a way to distinguish the upper class from peasants engaged in field work.