Science shows that when it comes to feeding a baby, breast is always best. Yet another study shows why mothers should always nurse whenever possible, but this time for their benefit: Breastfeeding may lower moms’ risks of heart attack and stroke.
For 10 years, researchers followed and tracked heart events in nearly 290,000 women in China who answered questions about how many children they had, whether they breastfed, and for how long. 
Women who breastfed their babies had a 9% lower risk of developing heart disease during the study period compared to women who didn’t breastfeed. Women who breastfed more than 1 baby for 2 years or more lowered their risk of heart disease 18%, and their risk of stroke by a similar amount, compared to moms who never breastfed.
The effect persisted after researchers adjusted for factors that can affect heart attack risk, including cholesterol levels, blood pressure, smoking, obesity, and physical activity.
To be clear: The findings don’t mean that women who don’t breastfeed will suffer a heart attack or stroke. If you decide not to breastfeed for some reason, you shouldn’t assume you’re going to suffer a major health event because of it.
Researchers need to do a little more digging to find out why breastfeeding seems to lower heart attack and stroke risk. But one possibility is that breastfeeding changes the metabolism of women after they give birth, according to study author co-author Sanne Peters, a research fellow in epidemiology at the University of Oxford in England.
During pregnancy, fat is accumulated and redistributed throughout the body to ensure the developing baby has plenty of nutrients, and to prepare to nurse the baby with breast milk. Past studies indicate that breastfeeding makes it easier for the body to get rid of that accumulated fat.
“Women who don’t breastfeed essentially have metabolic reserves that they don’t need.”
To put it in simpler terms, women who don’t breastfeed may gain more weight or not shed weight as easily as women that do, and that, in turn, could increase their risk factors for heart disease, such as unhealthy cholesterol levels and atherosclerosis.
Dr. Nieca Goldberg, a spokesperson for the American Heart Association, theorizes that breastfeeding mothers might have healthier habits overall compared to moms who don’t breastfeed. That is to say, the findings may be more of a correlation than a cause-and-effect, though perhaps both are true.
It’s possible that breastfeeding has direct effects. For example, oxytocin, a feel-good hormone released during breastfeeding, might play a direct role in the lowered heart attack and stroke risks, as the hormone causes the blood vessels to relax. 
It’s not clear for how long moms need to breastfeed to reap the most heart benefits. In China, the average breastfeeding time is about a year. In the U.S., it’s closer to 6 months.
In the study, no differences were found between breastfeeding moms and bottle-feeding moms in terms of body mass index (BMI). But Peters said future studies should take into account more factors that affect heart health, including blood sugar, blood pressure, and cholesterol levels.
The researchers found that the longer a woman breast-fed, the lower the risk. For each additional 6 months of breastfeeding per baby, the risk of cardiovascular problems declined by 3-4% on average.
So, breastfeed if you can, but if you can’t, don’t worry. Goldberg said:
“Certainly, [moms] can lower their risks by getting regular exercise, not smoking, managing stress, and eating a healthy diet – like the Mediterranean diet.”