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Breast-feeding women lower their risk of type 2 diabetes, study finds

Women who breast-feed have a lower risk of developing type 2 diabetes, according to new research.
The study, conducted by researchers at Kaiser Permanente Northern California, found that women who have had gestational diabetes who breast-feed for more than two months reduce their risk of type 2 diabetes by 50 per cent. The longer women breast-fed, the more they lowered the risk of type 2 diabetes.
Why might breast-feeding lower the risk of type 2 diabetes?
The researchers identified several ways in which breast-feeding helps to reduce the risk of type 2 diabetes.
“Lactation gives the insulin-producing cells in the body a rest because they don’t have to make so much insulin to lower blood glucose,” said study author Erica Gunderso, a senior research scientist at Kaiser Permanente Northern California. “Breast-feeding uses up glucose and fat in the blood because these nutrients are transferred from the bloodstream into the breast tissue for milk production.”
Following pregnancy, the body has to produce much more insulin to keep blood glucose levels under control, and this heightened insulin production increases the risk of insulin resistance. Because breast-feeding reduces glucose levels, it reduces the need for such high levels of insulin production, thereby reducing the risk of insulin resistance, which often leads to type 2 diabetes.
Moreover, breast-feeding has been linked to a “reset” in the body’s metabolism, restoring a metabolic calm after the chaos of pregnancy.
Gunderson was keen to point out “this is not about weight loss.” After all, some women who breast-feed don’t lose weight. “There’s a lot of variability in how women respond to pregnancy and lactation and in terms of what their body does.
How was the study conducted?
The researchers examined data from more than 900 women two years after they had developed gestational diabetes during pregnancy. During this two-year period, 12 per cent of the women developed type 2 diabetes.
The women were split into five groups: the first fed their babies only through breast-feeding; the second used only formula feeding; the third used mostly breast-feeding (less than six ounces of formula per day); the fourth used mostly formula (more than 17 ounces of formula per day); and the fifth group used mixed feeding (7 to 17 daily ounces of formula).
The women in the exclusive breast-feeding group were 54 per cent less likely to develop type 2 diabetes than women who only used formula. Even the women who fed their babies a mixture of formula and breast milk reduced their risk of type 2 diabetes by more than a third compared to the formula-only group, suggesting that even a small amount of breast-feeding is beneficial.
There were also links between type 2 diabetes risk and the length of time spent breast-feeding. Compared to breast-feeding for two months or less, women who breast-fed for more than 10 months had a 57 per cent reduction in type 2 diabetes risk. When women breast-fed their babies for between two and 10 months, they halved their risk of type 2 diabetes compared to those who breast-fed for less than two months.
How are the findings linked to gestational diabetes?
Dr. Aaron Caughey, chair of obstetrics and gynecology at Oregon Health and Science University School of Medicine in Portland, explained that the findings were particularly important because women who develop gestational diabetes are less likely to breast-feed.
“Women with high rates of pregnancy complications, including gestational diabetes mellitus, are less likely to breast-feed,” Caughey said.
“We think the chaos of having a pregnancy complication may lead to a decreased attention to focus on breast-feeding.”
Dr. Sherry Ross, an obstetrician and gynecologist at Providence Saint John’s Health Centre in Santa Monican, California, agrees that other complications can make breast-feeding difficult for women who have had gestational diabetes.
“Creating strategies to reduce the risk of diabetes should begin during pregnancy and continue once the baby is bor,” Ross said.
“In addition to breast-feeding, other lifestyle behaviours such as weight loss, dietary changes and increasing physical activity all reduce the future risk of diabetes.”
The findings could have implications on healthcare policy. Gunderson believes that more must be done to promote breast-feeding to women at a high-risk of type 2 diabetes, such as those who are obese or those who had gestational diabetes.
“The main policy implication is that we need to focus our breast-feeding promotion efforts to high-risk women, those who are obese or have a pregnancy with gestational diabetes,” said Gunderson.
It is important to note that the study did not find a causal link between breast-feeding and lower risk of type 2 diabetes. Rather, the researchers found a correlation between time spent breast-feeding and lower risk of type 2 diabetes. Further studies would be needed to prove that breast-feeding definitely causes a lower risk of type 2 diabetes in the mother.
The findings are published in the Annals of Internal Medicine.

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