The researchers, led by Sally Grantham-McGregor of University College London, examined information on childhood poverty from UNICEF and height statistics from the World Health Organization (WHO).
Grantham-McGregor and colleagues studied information on 156 countries -- 126 of which frequently stunt children's growth and 88 of which have a portion of the population living in absolute poverty -- and found that 219 million of 559 million children fail to reach normal cognitive development, which can affect their learning ability and career later in life.
According to Grantham-McGregor, malnutrition -- especially iron and iodine deficiency -- is largely to blame for children's failure to reach full intellectual potential. However, an additional problem is that parents often fail to stimulate their children's intellect with learning activities that spur brain development.
"It's critical to improve the environment of these kids so they don't suffer deficits in cognitive development," Grantham-McGregor said. "The parents don't realize that they input can make a difference. They really need demonstrations" to teach them how to stimulate their children's minds, she said.
Grantham-McGregor recommends worldwide governments -- especially those of developing countries, where the problem is most widespread -- invest in simple, low-cost programs to boost kids' brainpower, which she says can help break the cycle of poverty.