But the findings may be less true for obese women, according to the study published in the American Journal of Hypertension.
Researchers at the U.S. and South Korea looked at 3,119 non-smoking postmenopausal women aged 50 years or older in the 2010-2011 Korea National Health and Nutrition Examination Survey.
They found that more children breastfed and longer duration of breastfeeding were associated with lower risk of hypertension in postmenopausal women.
In particular, the highest quintile of number of children breastfed (5 to 11) showed a 51 percent lower risk of hypertension compared with the lowest quintile (0 to 1).
The highest quintile of duration of breastfeeding (96 to 324 months) showed a 45 percent lower risk of hypertension.
One mechanism proposed to underlie the breastfeeding-hypertension relationship was that maternal metabolism may be "reset" by breastfeeding after pregnancy, which decreases the risk of obesity-related diseases.
Another mechanism was that oxytocin release stimulated by breastfeeding may be associated with the decreased risk of these diseases.
"Our findings endorsed the current recommendations for breastfeeding for the benefit of maternal health in mothers' later lives," said the paper's lead researcher, Nam-Kyong Choi at the Ewha Womans University in South Korea.
But the researchers added that greater obesity and insulin resistance significantly attenuated the protective effects of breastfeeding.
Previously, long-term breastfeeding has been linked to a number of health benefits, including reduced children's allergies, celiac disease, obesity and diabetes.
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