It would also prevent more than 800,000 child deaths, and about 20,000 breast cancer deaths every year.
“Breastfeeding saves lives and money in all countries, rich and poor alike,” said Cesar Victora from the Federal University of Pelotas in Brazil, one of the authors of a research series published by The Lancet medical journal.
“There is a widespread misconception that the benefits of breastfeeding only relate to poor countries. Nothing could be further from the truth,” he said in a statement.
The findings were based on analysis of 28 scientific reviews and meta-analyses that looked at the proven health and economic benefits of breastfeeding.
The authors said this was the largest and most detailed analysis of its kind ever done.
It concluded that breastfeeding led to a “dramatic” improvement in life expectancy.
In high-income countries, it reduced the risk of sudden infant deaths by more than a third. In low-and middle-income countries, it could prevent about half of diarrhoea episodes and a third of respiratory infections.
Altogether, about 800,000 children’s lives could be saved every year — the equivalent of about 13% of all deaths in children under two years.
“It also increases intelligence,” said the statement.
“Modelling conducted for the series estimates that global economic losses of lower cognition from not breastfeeding reached a staggering $302bn in 2012.” This was about half a percent of the world’s gross national income.
Last year, a study in The Lancet Global Health journal said breastfeeding led to increased adult intelligence, longer schooling and higher adult earnings, regardless of family background. That research had tracked the development of 3,500 people in Brazil over 30 years from birth.
The new series said boosting breastfeeding rates for children under six months to 90% in the US, China and Brazil, and to 45% in Britain, would dramatically cut treatment costs of common childhood illnesses such as pneumonia, diarrhoea and asthma.
In the US, the saving would be $2.45bn, in Britain $29.5m, in China $223.6m and in Brazil $6m.
For women, longer breastfeeding has been shown to reduce the risk of breast and ovarian cancer, the study authors said, and estimated that some 20,000 women’s deaths could be prevented per year.
Yet, one in five children in high-income countries is breastfed to 12 months, and one in three in low-and middle-income countries is exclusively breastfed for the first six months of their lives.
In Britain, about 1% of children are breastfed until the age of one, in Ireland about 2% and in Denmark 3% — among the lowest rates in the world.
Breastfeeding is much more common in poor countries.
Breast milk is free, nutritious and protective against disease, but not always practical for women who cannot be on call around the clock. In some societies, it is frowned upon to breastfeed in public.
And in some cases, it can be dangerous — breastfeeding can pass on HIV from infected mothers to their children.
“Currently, breastfeeding promotion focuses on encouraging women to breastfeed without providing the necessary economic and social conditions such as supportive healthcare systems, adequate maternity entitlements and workplace interventions, counselling and education,” said co-author Nigel Rollins from the World Health Organisation.
Another problem was “aggressive marketing” of breast milk substitutes — with global sales set to reach $70.6bn by 2019.
The researchers called for political commitment and financial investment to make it easier for women to breastfeed, and tighter regulation of the breast milk substitute industry.