It was the first study of its kind to identify tangible benefits of breastfeeding later in life.
Hawke's Bay District Health Board breastfeeding adviser Liz Banks said breastfeeding was about more than just nutrition.
"The latest neuroscience research has shown that sensory stimulations occur during the bonding relationship between mother and child.
"This relationship helps lay the foundation for the child's future social and emotional intelligence." The World Health Organisation also recognised the importance of breastfeeding for social and emotional well-being, she said.
Hawke's Bay's maternity service promoted breastfeeding as the normal, optimum nutrition for babies, but women who chose not to breastfeed were given full support and education around safe formula feeding, Mrs Banks said.
Nationally there were some reports from mothers who felt pressured and inadequate for choosing not to breastfeed their baby, Mrs Banks said. "There are often very good reasons a mother has chosen not to breastfeed. Mothers have a choice and our job as health professionals is to provide advice and then support women in those choices."
Plunket figures show 81 per cent of Hawke's Bay babies up to the age of six weeks are getting some breast milk - 4 per cent lower than the national average. Hawke's Bay District Health Board data show 93 per cent of women initiated breastfeeding and almost 79 per cent breastfed exclusively from birth until discharge. Plunket New Zealand said the country's present breastfeeding rates were the highest in 19 years.
"The Ministry of Health recommends that babies are fed exclusively on breast milk for the first six months, not only for nutritional reasons but because breastfeeding also provides an ongoing opportunity for mums to bond with their baby," said Hawke's Bay clinical adviser Tracey Armstrong.
"Breastfeeding supports babies' physical and emotional development and is a great, natural way to help a mother and baby to get to know each other and build a loving relationship," she said.
As well as the emotional development, being breastfed also provided protection against illness and infections, including in adulthood. That included reducing the risk of allergies, eczema, asthma, reflux, some bowel diseases, some childhood cancers, obesity, and type 2 diabetes later in life.
Meanwhile, a US study has shown breast milk boosted brain development in babies by up to 30 per cent, especially in the parts of the brain that controlled language, emotion, and understanding.
The research, from Brown University in Rhode Island, found that children under four who were exclusively fed breast milk showed a discernible difference in their brain structure by the time they turned two.