Mothers who breastfeed their babies have a lower risk of developing or dying from heart disease than those who don't breastfeed, finds new research from the University of Sydney, Australia.

Published in Journal of the American Heart Association, the study of over 100,000 Australian mothers participating in the Sax Institute's 45 and Up Study found women who breastfed had a 14% lower risk of developing, and 34% lower risk of dying from, cardiovascular disease.

This is an important finding given that heart disease is the leading cause of death for women worldwide, says lead author Dr. Binh Nguyen, from the University of Sydney's School of Public Health and Charles Perkins Centre. "Our study suggests that among childbearing women, breastfeeding may offer long-term heart health benefits in addition to its known benefits for infants and mothers," said Dr. Nguyen. "We know that changing lifestyle factors such as weight and diet can significantly reduce risks of heart disease and we have taken this a step further by looking at lifestyle behaviors that are specific to women."

Senior author and associate professor Melody Ding, from the School of Public Health and Charles Perkins Centre, said further research was needed to explore why breastfeeding appears to show protective benefits for heart health. "At this stage we can't pinpoint why, but one of the likely theories is that the calories women expend breastfeeding, nearly 500 each day, are associated with positive changes in metabolism which help women that breastfeed to lower their risk of heart disease."

About the study

Researchers from the University of Sydney, Australia linked retrospective survey data on breastfeeding from 2006 to 2009 from the Sax Institute's 45 and Up Study—the largest ongoing study of healthy aging in the Southern Hemisphere—with hospital admission and death data.

Women who had existing heart health issues were excluded from the study and substantial adjustments were made to take into account socio-economic influences and concurrent lifestyle risk factors.

Key findings:

• In women who have had children, breastfeeding compared to never breastfeeding was associated with a 14% lower risk of developing and a 34% lower risk of dying from cardiovascular disease
• In women who breastfed on average up to 12 months per child, a 15% lower risk of developing and a 30%–40% percent lower risk of dying from cardiovascular disease were found compared to women who never breastfed
• Findings were independent of socioeconomic status and overall health-related lifestyle

While breastfeeding and cardiovascular health is a growing area of interest, there is still limited research in this area. The new longitudinal study builds on a systematic review by the team published in PLOS ONE in 2017, which found some evidence of the protective role of breastfeeding for cardiovascular risk factors such as hypertension. However, the few studies on cardiovascular disease incidence and mortality showed mixed results, which motivated the researchers to conduct the current study.

Sax Institute deputy CEO Dr. Martin McNamara said the 45 and Up Study continues to reveal new insights about the health of Australians. "Our ability to follow people for such a long time is driving important new findings—in this case the link between breastfeeding and cardiovascular outcomes," he said.