One of the world's most prestigious medical journals has confirmed breastfeeding's positive effect on mothers' and babies' health.
The Lancet has published a series on the health benefits of breastfeeding across low, middle and high income countries, analysing 28 pieces of research which studied breastfeeding's effect on children's mortality, diarrhoea, respiratory infections, "swimmer's ear", eczema, food allergies, hay fever, asthma, infant growth, and dental health.
The researchers from Brazil, Switzerland, New York, Baltimore and New Delhi also studied breastfeeding's effect on mothers' risk of temporary postnatal infertility, breast and ovarian cancers, type-2 diabetes, postpartum weight change and osteoporosis.
The meta-analysis is to date the most comprehensive and statistically robust analysis of 30 years of breastfeeding research.
The study reported that breastfeeding had a strong protective effect on infant mortality on low and high income countries. For the latter, breastfeeding was associated with a 36 per cent reduction in sudden infant deaths, and a 58 per cent reduction in necrotising enterocolitis, an often-fatal condition in which a portions of an infant's bowel tissue dies.
The authors note that mothers in high income countries breastfed their babies for shorter durations than those in low or middle income countries. Fewer than one in five children in high-income countries are breastfed by 12 months of age.
The authors estimated increasing breastfeeding in high income countries from present levels to 12 months would result in saving 22,216 lives globally per year. They estimated failing to breastfeed cost the world's economy about NZ $470 billion.
The authors of the study also reported breastfeeding was associated with a higher performance in intelligence tests in children and adolescents, with results from various studies showing an increase of between 2.6 - 7 pooled IQ points.
Other benefits included a 26 per cent reduction in the risk of children becoming overweight or obese across income groups, the study found.
Surprising findings included no clear evidence of breastfeeding's protective effect against food allergies or eczema, and an association between increased tooth decay in children and breastfeeding for longer than 12 months.
"This observation should not lead to discontinuation of breastfeeding, but rather to improved oral hygiene," the authors' clarified.
They also reported better-educated women from high-income countries were more likely to breastfeed their babies than those in low income, low education groups, which could leading to some confounding of the health benefits of breastfeeding in the high income groups.
"There is a strong child health and public health case for ensuring that women are encouraged to breastfeed," said UNICEF New Zealand's National Advocacy Manager Deborah Morris-Travers.
"Supporting breastfeeding is not about stigmatising those who can't feed for some reason, it is simply about making sure that people know the facts and that it is in baby's best interests to be breastfed for as long as possible."