Breastfeeding slashes women's risk of developing high blood pressure - the single biggest cause of disease and death, according to new research.
A study of more than 3,000 women found those who nursed infants were up to 51 per cent less likely to become hypertensive as they got older.
The more babies they had, and the longer they breastfed, the greater the protection, scientists said.
Rates of breastfeeding in the UK are the lowest in the world.
It is well known long term breastfeeding boosts children's health - reducing infections, sudden infant death syndrome (SIDS), diabetes, obesity and even leukaemia and heart disease.
But the benefits for mothers have been little studied compared to those for their offspring.
So in the first study of its kind the researchers analysed 3,119 non smoking postmenopausal women aged 50 years or older in Korea.
Those who breast fed at least five children were 51 per cent less likely to have high blood pressure, or hypertension, compared to one or none.
And participants in the highest fifth for breastfeeding duration of 96 months or more showed a 45 percent reduced risk.
Dr Nam-Kyong Choi, of Ewha Womans University, Seoul, said: "Our findings endorsed the current recommendations for breastfeeding for the benefit of maternal health in mothers' later lives."
The study published in the American Journal of Hypertension suggests women who breastfeed more children, and for longer periods of time, are less likely to suffer from hypertension after they reach menopause.
But the effects were lessened for obese women and those with insulin resistance, which can lead to type 2 diabetes, the form linked to an unhealthy lifestyle.
High blood pressure is the greatest single risk factor for disease and mortality.
It affects three in ten British women and can lead to heart attacks, strokes and even dementia, three of the UK's biggest killers.
Dr Choi said previous research has found women who don't breastfeed, or stop prematurely before six months, have a higher risk of diabetes and cardiovascular diseases.
But this is the first time a clear relationship between breastfeeding and hypertension has been established.
Dr Choi explained maternal metabolism, such as fat accumulation and insulin resistance, may be 'reset' by breastfeeding after pregnancy, which decreases the risk of obesity related diseases.
The brain chemical oxytocin, dubbed the 'cuddle hormone' as it is released during sex, is boosted by breastfeeding and may also be protecting against illnesses.
Dr Choi said: "Elevated blood pressure is the greatest single risk factor for the worldwide burden of disease and mortality.
"High blood pressure explained 9.4 million deaths and 7 per cent of global disability-adjusted life years in 2010.
"In 2000, 26.4 per cent of adults worldwide or 972 million had hypertension, and 29.2 per cent or 1.56 billion are expected to have it by 2025.
"With global increases in elderly populations and in cardiovascular diseases, the prevalence of hypertension is consistently expected to increase and to remain a major public health challenge."
The World Health Organisation and the American Academy of Paediatrics commonly recommend exclusive breastfeeding for six months, with ongoing partial breastfeeding after complementary foods are introduced.
Added Dr Choi: "Breastfeeding fewer children and short-term breastfeeding were associated with higher risk of hypertension in postmenopausal women; 10.2 per cent and 6.5 per cent of the hypertension in our study population could be attributed to three or fewer children breastfed and breastfeeding for 56 months or less, respectively.
"Our findings endorsed the current recommendations of breastfeeding for the benefit of maternal health in mothers' later lives.
"Greater attention should be paid to breastfeeding in developing more effective hypertension prevention strategies in parous postmenopausal women.
"Prospective studies are required to address the mechanisms of breastfeeding-induced hypertension."
Department of Health guidelines urge all mothers to breastfeed their children exclusively for the first six months of life, if they are able to.
Previous US research has found women who gave their babies formula or breastfed for less than three months were almost a quarter more likely to develop blood pressure problems.
The study of 56,000 women with at least one child estimated up to 12 per cent of high blood pressure cases among women with children could be linked to "suboptimal" breastfeeding.
In the UK only one in 200 women - or 0.5 per cent - is still doing any degree of breastfeeding after a year, research has shown.
That compares with 23 per cent in Germany, 56 per cent in Brazil and 99 per cent in Senegal.
In the UK, 81 per cent of mothers have tried breastfeeding at some point, but only 34 per cent are breastfeeding at six months and 0.5 per cent at 12 months.