A meta-analysis of 28 studies has concluded 800,000 babies' lives could be saved each year through additional breastfeeding. Meanwhile, 20,000 mothers would avoid dying from breast cancer in the process.

Most of the lives that breastfeeding could save are in places where the water supply is unsafe. Since formula needs to be mixed with water, infants' undeveloped immune systems often cannot protect them against the pathogens. The rapid expansion of clean water supplies over the last twenty years has slashed the number of children exposed to contaminated water, and with it the number of deaths, which once exceeded a million a year.

However, this is far from the whole story. "There is a widespread misconception that the benefits of breastfeeding only relate to poor countries. Nothing could be further from the truth," said Professor Cesar Victora from the Federal University of Pelotas in Brazil in a statement. Victora is the lead author of the first paper in a series of studies, published in The Lancet, measuring the worldwide impact of breastfeeding.

"Our work for this series clearly shows that breastfeeding saves lives and money in all countries, rich and poor alike,” he said. “Therefore, the importance of tackling the issue globally is greater than ever.”

By commissioning 22 new studies for the series, using funding from the Bill & Melinda Gates Foundation and the Wellcome Trust, Victora and his coauthors were able to explore the multiple contexts in which the decision to breastfeed or not can matter.

Even in high-income countries, breastfeeding reduces the risk of sudden infant deaths by a third, with economic as well as humanitarian benefits. Breastfeeding is associated with better cognition, and if all babies were given a full opportunity to breastfeed the paper puts the value of the potential long-term economic boost at $302 billion (£211.6 billion), 0.49 percent of global income.

"Breastfeeding is one of the few positive health behaviors that is more common in poor than richer countries, and within poor countries, is more frequent among poor mothers," said Victora. He noted that the U.K. rate of breastfeeding at 12 months is less than 1 percent, the lowest in the world, adding, "The stark reality is that in the absence of breastfeeding, the rich-poor gap in child survival would be even wider."

While the paper calculates the benefits if 90 percent of babies in the U.S. and China were breastfed for 12 months, bottles are so dominant in the U.K. that the authors set a more realistic 45 percent target for the U.K.

The choice of 90 percent reflects the fact that some mothers are unable to breastfeed for a variety of reasons. In most cases, however, low rates of feeding are attributed to lack of support, misleading (and often deliberately dishonest) promotion of milk substitutes and obstacles to breastfeeding in public. Nevertheless, the authors draw hope from examples such as Brazil, which over 30 years has taken the average breastfeeding period from 2.5 to 14 months through policy and cultural change.