Breastfeeding is not only healthy for babies, it may also help to reduce mothers’ risk of having a heart attack or stroke later in life, according to new research published in the Journal of the American Heart Association. The work is based on a large prospective cohort study of 300,000 adult women in China.

Previous studies have suggested that mothers derive short–term metabolic health benefits from breastfeeding, such as a lower cholesterol, blood pressure, and glucose levels and weight loss after pregnancy. However, the long–term effects of breastfeeding on risk of developing cardiovascular disease in mothers are unclear. A new study in China found that women who ever breastfed their babies had significantly lower risk of developing cardiovascular disease such as heart disease or stroke, and the longer they breastfed, the greater effects they had.

Researchers from the University of Oxford, Peking University and the Chinese Academy of Medical Sciences studied 300,000 women aged 30–79 years, as part of the prospective China Kadoorie Biobank of 0.5 million adults, from 10 urban and rural areas across China, tracking their health through hospital records of illness and death registries. After 8 years of follow–up, there were 16,671 cases of coronary heart disease which includes heart attacks, and 23,983 stroke cases among the 290,000 women who had no previous history of cardiovascular disease when enrolled in the study.

Researchers observed that:

• Nearly all gave birth and 97 percent of the women breastfed each of their babies for an average of 12 months.
• Compared to women who had never breastfed, mothers who ever breastfed their babies had a 9 percent lower risk of heart disease and an 8 percent lower risk of stroke.
• Among mothers who breastfed each of their babies for two years or more, heart disease risk was 18 percent lower and stroke risk was 17 percent lower than among mothers who had never breastfed.
• Each additional 6 months of breastfeeding per baby was associated with a 4 percent lower risk of heart disease and a 3 percent lower risk of stroke.

Results from observational studies such as this one need to be confirmed by a different type of study that can prove cause and effect. Women who breastfeed may be more likely to engage in other beneficial health behaviours that lower their risk of cardiovascular diseases than women who do not breastfeed. However, the researchers took into account a range of risk factors for cardiovascular disease, including smoking, high blood pressure, obesity, diabetes and physical activity that could have biased results. So the observed beneficial effects of breastfeeding are independent of these and other lifestyle factors. The large number of women that were included in the study are among the main strengths of the current study.

Study author Dr Sanne Peters, research fellow from The George Institute for Global Health at the University of Oxford, said, “Although we cannot establish the causal effects, the health benefits to the mother from breastfeeding may be explained by a faster “reset” of the mother’s metabolism after pregnancy.”

Pregnancy changes a woman’s metabolism dramatically as she stores fat to provide the energy necessary for her baby’s growth and for breastfeeding once the baby is born. Breastfeeding could eliminate the stored fat faster and more completely, leading to reduced risk of cardiovascular diseases later in life.

Co–author, Professor Liming Li from the Peking University, commented, “Nearly all women in the study were born before 1970s and the rate of breast feeding was much higher than that in the Western populations and younger generations in China.”