Researchers at the University of California say that a study of rhesus monkeys finds that breast-feeding is healthier for infants.
Scientists monitored 10 baby rhesus monkeys for three months, comparing the development of five monkeys were breast-fed to that of five who were fed formula. Within a month, formula-fed monkeys had outgrown the breast-fed monkeys, the Daily Mail notes.
The faster growth was linked to higher amounts of protein in the formula. Rhesus breast milk is 11.6% protein, compared to 18.3% in formula. By contrast, human breast milk is 8% protein.
Formula-fed monkeys also showed higher levels of insulin in their blood The researchers said the study signaled that formula feeding could set metabolic trends that carry on to adulthood, leading to obesity.