Drinking lots of sugar-sweetened cola may increase women’s likelihood of developing diabetes during pregnancy, a condition known as gestational diabetes, new research shows.

Compared to women who had less than one such beverage a month, women who drank at least five servings of non-diet cola a week were at greater risk of gestational diabetes, even after accounting for their body mass index (BMI), level of physical activity, and other diabetes risk factors, researchers found.

Sugar-sweetened beverages are the top source of added sugar in US diets, and several studies have linked high sugary drink intake with an increased risk of type 2 diabetes in women, Dr. Liwei Chen of the Louisiana State University Health Science Center in New Orleans and colleagues note in the latest edition of the journal Diabetes Care.

But there is little information on whether consumption of sugar-sweetened beverages before pregnancy might increase gestational diabetes risk, they add.

To investigate, the researchers analyzed data from the Nurses Health Study II, looking at 13, 475 women who had at least one pregnancy between 1992 and 2001. During that time, 860 women reported having been diagnosed with gestational diabetes for the first time.

Women who drank five or more sugar-sweetened beverages of any type per week were 23 percent more likely to develop gestational diabetes than those who drank less than one serving a month, and the relationship remained even after the researchers accounted for other gestational diabetes risk factors such as BMI and family history of diabetes.

But accounting for a Western-style diet - heavy in red meats, processed meats, sweets, snacks and other less-healthy foods - did explain some of the association between diabetes and sugary drinks.

The researchers looked separately at cola beverages, because the caramel coloring used in them has been linked in animal studies to insulin resistance and inflammation. They found a 22 percent increased risk of developing diabetes during pregnancy for women who drank five or more non-diet colas a week, compared to women who had less than one serving of cola a month.

There was no relationship between diet beverage consumption and gestational diabetes risk.

The demands pregnancy puts on a woman’s metabolism may “unmask” a tendency toward developing diabetes and similar conditions, Chen and colleagues note. Drinking cola could contribute to this tendency by making for a sugar-filled diet, they add, which in and of itself may be harmful to the insulin-producing beta cells of the pancreas.

Because diet cola didn’t increase gestational diabetes risk, they add, caramel coloring isn’t likely to be a major factor in the relationship observed with non-diet cola.

The findings “are particularly relevant” given that so many people drink sugar-sweetened cola, the researchers write. They call for more research on sugar-sweetened beverage consumption and gestational diabetes, as well as other pregnancy outcomes.

SOURCE: Diabetes Care, December 2009.