Breastfeeding as recommended - for a total of one year and exclusively for six months - could protect babies and their moms from premature death and serious diseases, researchers said.
The study underscores the importance of policies that make it possible for women to breastfeed, according to study senior author Alison Stuebe from the University of North Carolina in the US.
Researchers said their findings highlight the importance of providing women with the support they need to breastfeed their babies, beginning at birth.
"Breastfeeding is far more beneficial in preventing disease and reducing costs than previously estimated," said lead author Melissa Bartick, assistant professor of medicine at Harvard Medical School in the US.
"The results should compel all hospitals to develop programs aimed at helping new mothers learn to breastfeed their babies," said Bartick.
Researchers modelled two groups for the study. The 'optimal group', in which the majority of mothers breastfed as recommended and the 'suboptimal group', in which mothers breastfed at current rates in the US, which are less than the recommended guidelines.
Using existing research and government data, they projected the rates and costs of diseases that breastfeeding is known to reduce, along with the rates and costs of early deaths from those diseases.
Children's diseases included in the evaluation were acute lymphoblastic leukaemia, ear infections, Crohn's disease, ulcerative colitis, gastrointestinal infections, lower respiratory tract infections, obesity, necrotising enterocolitis and Sudden infant death syndrome (SIDS).
For mothers, the study included breast cancer, pre-menopausal ovarian cancer, diabetes, hypertension and heart attacks.
The researchers found that suboptimal breastfeeding was associated with more than 3,340 premature deaths in the US each year, costing the country 3 billion dollars in medical costs, 1.3 billion dollars in indirect costs and 14.2 billion dollars in costs related to premature deaths.
The majority of the excess death and medical costs - nearly 80 per cent - were maternal.
"Breastfeeding has long been framed as a child health issue, however it is clearly a women's health issue as well," said Eleanor Bimla Schwarz from University of California, Davis, in the US.
"Breastfeeding helps prevent cancer, diabetes and heart disease, yet many women have no idea breastfeeding has any of these benefits," said Schwarz.The study appears in the journal Maternal & Child Nutrition.