More than 800,000 child deaths could be prevented annually if more women around the world breastfed their babies, new research has found.
Experts claimed near-universal breastfeeding could also prevent 20,000 deaths from breast cancer each year.
The study, published in The Lancet medical journal, also showed breastfeeding increased intelligence and there was some evidence it protected against obesity and diabetes.
Scientists analysed data from 28 systematic reviews of previous research to show breastfeeding has a dramatic effect on life expectancy both for children and mothers.
In high-income countries, breastfeeding reduced the risk of sudden infant death by more than a third. It also had the potential to prevent about half of all infant cases of diarrhoea and a third of lung infections in low and middle-income countries.
The study revealed worldwide rates of breastfeeding were low, especially in high-income countries. In the UK, fewer than 1% of babies were breastfed up to their first birthday. In Ireland, the figure was 2% and 3% in Denmark.
Lead researcher Professor Cesar Victora, from the Federal University of Pelotas in Brazil, said:
There is a widespread misconception that breast milk can be replaced with artificial products without detrimental consequences.
Janet Fyle, from the Royal College of Midwives, said: "This report underpins and reinforces why breastfeeding is the most appropriate method of providing nutrition for a baby. It also highlights the pressing need to promote and increase the uptake of breastfeeding in the UK and globally."