Worldwide, breastfeeding rates are low and in the UK fewer than 1% of babies are breastfed until the age of 12 months.
The researchers analysed data from 28 systematic reviews of previous research, and also outlined other benefits, including: breastfed babies having higher IQs and less risk of infection and less risk of sudden infant death syndrome than those who are breastfed for shorter periods or not at all.
There was also some evidence that breastfeeding may offer protection against diabetes and obesity later in life; and for mums it may reduce the risk of ovarian cancer and type 2 diabetes.
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.
"The evidence, contributed by some of the leading experts in the field, leaves no doubt that the decision not to breastfeed has major long-term negative effects on the health, nutrition and development of children and on women's health."
Siobhan Freegard, founder of video parenting site Channel Mum commented that the UK's low breastfeeding rate isn't due to a lack of knowledge among mums about the benefits of breastfeeding.
"The very low UK breastfeeding rates aren’t down to a lack of education or lack of will from mums - they’re due to a lack of support and funding," she explained to HuffPost UK Parents.
“Mums know breast is best and four in five do try to breastfeed as soon as their baby is born.
"But breastfeeding is a skill that needs to be taught and nurtured. It can take hours to get it right and that means patience and perseverance, especially when new mums and exhausted and in pain.
"However overstretched maternity wards and overworked midwifes simply aren’t able to provide this kind of care right now, as they care coping with a baby boom and are thousands of midwives short.
"If we are serious about increasing breastfeeding rates, we need to invest more funds for more midwives to help mums nurse straight after birth and in the early weeks.
"The cost of this would be low in comparison with the long-term health benefits, as show in the Lancet report. It needs a long term view with long term benefits for mothers, babies and the entire NHS."
The new research also suggested incresing the number of breastfed infants aged under six months in the UK to 45% could save the NHS around £20 million.