During 10 years of follow-up, 860 women reported their first diagnosis of GDM among the 13,475 women included in this study. On average, women in this population consumed fewer SSBs than diet beverages. At baseline, the median intake was 1 serving/week for SSBs and 2–4 servings/week for diet beverages. The percentages of women who reported consuming SSBs of 0–3 servings/month, 2–4 servings/week, and ≥5 servings/week were 41.4, 27.3, and 33.3%, respectively. By volume, 34% of SSBs consumed was from sugar-sweetened cola and 66% was from other SSBs. For diet beverages, the percentages of women who reported consuming 0–3 servings/month, 2–4 servings/week, and ≥5 servings/week were 38.3, 15.3, and 46.4%, respectively. Of diet beverages consumed, 81% was from diet cola and 19% was from other diet beverages. Women with a higher intake of SSBs were on average younger and less likely to have a family history of diabetes or drink alcohol (). These women tended to consume a diet higher in total calories, total carbohydrates, processed and red meats, and glycemic load but lower in protein, fat, total dietary fiber, fruits and vegetables, and selected minerals and vitamins (magnesium, calcium, potassium, and vitamins C and E).
Baseline (1991) characteristics according to the frequencies of SSB consumption in 13,475 women
After adjusting for age and parity (; model 1), higher SSB intake was positively associated with GDM risk: compared with women who consumed <1 serving/month (reference group), RR for those who consumed ≥5 servings/week was 1.23 (95% CI 1.05–1.45; Ptrend = 0.005). The positive association between SSBs and GDM risk remained significant after adjustment for other demographic and lifestyle risk factors for GDM, including race, smoking, alcohol intake, physical activity, and family history of diabetes, in model 2 (Ptrend = 0.04). This association remained strong after additional adjustment for BMI (model 3). When SSB intake was treated as a continuous variable in model 3, each serving/day increment was associated with a 23% (95% CI 1.05–1.43; Ptrend = 0.01) increase in GDM risk. The association was slightly attenuated and became borderline insignificant (P = 0.06) with additional adjustment of Western dietary pattern (model 4). However, the trend for an elevated risk of GDM associated with increased SSB consumption persisted: the RRs (95% CIs) from the lowest to the highest SSB consumption category in model 4 were 1.00 (reference), 1.03 (0.87–1.23), and 1.16 (0.98–1.37). Further controlling for prudent dietary pattern and other beverage consumption including diet beverages and fruit juices did not change the results materially.
RR of GDM in relation to SSB consumption (n = 13,475; case subjects = 860)
In the stratified analysis according to participants' BMI status (<25 or ≥25 kg/m2), family history of diabetes (yes or no), smoking habit (never, past, or current smoking), or nulliparity (yes or no), the direction of the association between GDM risk and SSB consumption was consistent in each strata. The magnitude of the association, however, appeared to be stronger among nulliparous women (Pinteraction = 0.004).
Because caramel coloring in cola-type beverages has been positively associated with insulin resistance and inflammation in animals (16
), we further examined the associations between two types of SSBs (cola versus noncola) and GDM risk. A positive association with GDM risk was found for sugar-sweetened cola but not for noncola SSBs (). Compared with women who consumed sugar-sweetened cola of 0–3 servings/month, those who consumed ≥5 servings/week had a 22% increase in GDM risk (RR 1.22 [95% CI 1.01–1.47]; Ptrend
= 0.04) after controlling for other potential confounders (model 4).
We also assessed whether consumption of diet beverages was associated with GDM risk. For total diet beverages, the results did not show any association in all models, regardless of whether consumption was treated as a categorical variable or a continuous variable (). We further examined the relationship between two types of diet beverages (diet cola or other diet beverages) and risk of GDM. The consumption of other diet beverages showed positive associations in model 2. However, this positive association disappeared after additional adjustment for BMI and other dietary variables in models 3 and 4.
RR of GDM in relation to diet beverage consumption (n = 13,475, cases = 860)