Breast-Feeding Protects the Mother from Metabolic Syndrome

Breast-feeding may protect the nursing mother from metabolic syndrome, according to the results of a prospective, observational cohort study.

In a news release, lead author Erica Gunderson, PhD, from Kaiser Permanente’s Division of Research in Oakland, CA, said, “The Metabolic Syndrome is a clustering of risk factors related to obesity and metabolism that strongly predicts future diabetes and possibly, coronary heart disease during midlife and early death for women…. Because the Metabolic Syndrome affects about 18 to 37 percent of U.S. women between ages 20-59, the childbearing years may be a vulnerable period for its development. Postpartum screening of risk factors for diabetes and heart disease may offer an important opportunity for primary prevention.”

The multicenter, population-based US cohort used for this study consisted of 1,399 nulliparous women (39% black, aged 18 – 30 years) enrolled in the ongoing Coronary Artery Risk Development in Young Adults Study. Participants were free of the metabolic syndrome at baseline from 1985 to 1986 and before subsequent pregnancies. At 7, 10, 15, and/or 20 years after baseline, participants were re-examined, and National Cholesterol Education Program criteria were used to identify incident cases of metabolic syndrome.

The investigators used complementary log-log models to estimate relative hazards of incident metabolic syndrome among time-dependent lactation duration categories by gestational diabetes mellitus, after adjustment for age, race, study center, time-dependent parity, baseline body mass index, components of the metabolic syndrome, education, smoking, and physical activity.

Of 704 parous women, 84 had gestational diabetes and 620 did not. During 9993 person-years, there were 120 incident cases of metabolic syndrome, yielding an overall crude incidence rate of 12.0 per 1000 person-years (10.8 for nongestational diabetes and 22.1 for gestational diabetes). Increasing duration of lactation was associated with lower crude incidence rates of metabolic syndrome from 0 to 1 month through 9 months or more of breast-feeding (P < .001).

“The findings indicate that breastfeeding a child may have lasting favorable effects on a woman’s risk factors for later developing diabetes or heart disease,” Dr. Gunderson said.

Risk reductions associated with longer duration of lactation were greater among women with gestational diabetes (fully adjusted relative hazards range, 0.14 – 0.56; P = .03) vs those without gestational diabetes (fully adjusted relative hazards range, 0.44 – 0.61; P = .03).

Limitations of this study include observational design and possible residual confounding.

“Longer duration of lactation was associated with lower incidence of the metabolic syndrome years post-weaning among women with a history of GDM [gestational diabetes mellitus] and without GDM controlling for preconception measurements, BMI [body mass index], socio-demographic and lifestyle traits,” the study authors conclude. “Further investigation is needed to elucidate the mechanisms through which lactation may influence women’s cardiometabolic risk profiles, and whether lifestyle modifications, including lactation duration, may affect development of coronary heart disease and Type 2 diabetes, particularly among high-risk groups such as women with a history of GDM.”