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Thanks to public-health messages, everyone pretty much knows that breast-feeding is beneficial for baby. But it’s also really good for mom, and now a new study quantifies just how good.

If new moms adhered to the recommended guidelines that urge them to breast-feed each child they give birth to for at least one year, they could theoretically stave off up to 5,000 cases of breast cancer, about 54,000 cases of hypertension and nearly 14,000 heart attacks annually.

Averting those diseases could also save $860 million, according to research published in Obstetrics & Gynecology.

Those figures, while significant and intriguing, are not actual numbers from documented cases. Rather, they’re the result of a sophisticated statistical model used to compare the effect of current breast-feeding rates in the U.S. to ideal rates.

The study, led by Harvard researcher Dr. Melissa Bartick, simulated the experiences of about 2 million U.S. women from the time they were 15 until they turned 70, estimating outcomes and cumulative costs over the decades in between.

Number crunchers ran the data applying current breast-feeding rates — about 25% of U.S. women breast-feed for the recommended 12 months per child — and again assuming that 90% of women embraced the guidelines. “To be totally scientifically accurate, those are costs for a cohort of women in a certain year,” says Bartick, an assistant professor of internal medicine at Harvard Medical School. “If breast-feeding rates change, the cost would be different.”

(MORE: 20 Ways to Make Breast-Feeding Easier)

Still, she says, the point is that breast-feeding boosts mom’s health in a big way. “We know that 60% of women don’t even meet their personal breast-feeding goals, whether it’s three or four or six months,” says Bartick. “We need to do more to support women so they can breast-feed longer. There are thousands of needless cases of disease and death that could be prevented.”

Multiple factors played a role in the calculations, including number of deliveries, breast-feeding duration and whether the women developed five diseases — breast cancer, premenopausal ovarian cancer, hypertension, heart attack and Type 2 diabetes — that were selected based on previous research showing that breast-feeding affects a woman’s risk of diagnosis. But this study did not find significant effects for ovarian cancer, which Bartick attributed to ovarian cancer occurring infrequently, nor diabetes, which was looked for only within 15 years of delivery.

Researchers also examined death rates from the panel of diseases, concluding that the cost to society of women dying before 70 — 11 years shorter than the average U.S. woman’s life expectancy — totals $17.4 billion. The amount derives from an economic model that uses age to value a human life.

Drilling deeper, the study found that less-than-optimal breast-feeding rates took a $734 million toll in terms of hospital stays, doctor visits and medication and cost $126 million in time away from work.

The conclusions, says Dr. Kathleen Marinelli, a neonatologist and chair-elect of the U.S. Breastfeeding Committee, represent a “very elegant mathematical and statistical look at the health costs to women and society of not breast-feeding optimally in the U.S.”

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The cost analysis is a companion to a 2010 Pediatrics study that looked at how low breast-feeding rates impact disease in children. That research, also led by Bartick, attributed 911 deaths among kids each year and annual costs of $13 billion to not following breast-feeding guidelines.

After that study was published, says Bartick, “we got a million inquiries saying, That doesn’t include the women! We wanted a complete picture.”

And now they have it, to some extent. Detractors, of course, may pooh-pooh the simulation aspect of the study. And even Bartick notes that it’s impossible to know for sure if breast-feeding itself causes less disease or if women who breast-feed simply have healthier habits. The grant, from the W.K. Kellogg Foundation, helped fund a “causal-inference expert” who advised the researchers on whether they could accurately claim that breast-feeding was affecting disease risk and was not simply an association. “His opinion was there was enough evidence to suggest it was causal,” says Bartick.

The study points to the need for more support for mothers who want to breast-feed — everything from employers providing a clean, private space to pump milk to strangers learning not to gawk when a woman nurses her baby on a park bench. “What’s really important are not the numbers they came up with,” says Marinelli. “What’s important is that it tells us that the cost of not providing support to women to optimally breast-feed their babies is astronomical because of the known health benefits to women. This points out that breast-feeding is not a lifestyle choice; it’s a public-health imperative.”

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