Evidence is emerging that sugar-sweetened beverages may have uniquely detrimental effects on health, even compared to other sources of sugar. Previous research shows the impact of sugar on insulin and glucose concentrations in the blood depends on the type, amount, and rate of digestion of the sugar consumed. Compared to other sugars in whole foods, sugars in beverages are metabolized and absorbed more quickly. Glucose levels in the blood rise higher and fall lower with the consumption of sugar-sweetened beverages compared to whole foods. Such unique characteristics of sugar-sweetened beverages may explain the higher risks of obesity and type 2 diabetes.
Building on this previous research, a recent study examined the potential association with two forms of uterine cancer in postmenopausal women. These researchers compared the uterine cancer risks associated with sugar-sweetened beverages, fruit juice, sugar-free beverages, sweets/baked goods, starch, and other sugars in a population of 23,039 postmenopausal women in the Iowa Women’s Health Study.
The two types of uterine cancer investigated were type I and type II endometrial cancer. Over the period examined from 1986 to 2010, there were 506 cases of type I and 89 cases of type II cancer diagnosed in the study population. Factoring in sugar-sweetened beverages, the researchers found an increased risk of the more common type I cancer for drinkers of sugar-sweetened beverages. In terms of diet and physical activity, compared to non-drinkers of sugar-sweetened beverages, women who drank more than four sugar-sweetened beverages per week consumed an additional 583 calories per day. Additionally, of the non-drinkers of sugar-sweetened beverages, 44 percent reported low levels of physical activity, compared to 56 percent of sweetened beverage drinkers who consume more than four of these beverages per week.
Looking at uterine cancer risk, the top 20 percent of sugar-sweetened beverages drinkers (an average of 3.3 servings per week) had a 78 percent greater risk of developing type I uterine cancer than non-drinkers. This greater risk was still observed even after body mass index, physical activity, history of diabetes, and cigarette smoking were taken into account. Importantly, high consumption of fruit juice, which has high naturally occurring sugar content, was not associated with greater cancer risk. When total fruit juice and sugar-sweetened beverages consumption together was examined, there was a 48 percent higher risk of the type I uterine cancer among the top 20 percent of consumers (who averaged 13 total servings per week), compared to the bottom 20 percent. The strength of both of these associations was stronger when body mass index was taken into account. In contrast to the sugar-sweetened beverage findings, in the overall population sweet/baked goods, starch intake, and the intake of specific sugar types (sucrose, fructose, or glucose) were not associated with any increase in uterine cancer risk. When individuals with diabetes were excluded from the analysis, the highest consumers of these types of sugars did have a higher risk, a 23 percent increase for sucrose, a 32 percent increase for fructose, and a 50 percent increase for glucose.
Sugar-sweetened beverage consumption is also associated with higher levels of obesity, which has been identified as a major risk factor for uterine cancer. However, this study shows an association of sugar-sweetened beverages even when body mass is taken into account. The lack of associations of sweets/baked goods and specific sugars within the population as a whole with the type I uterine cancer examined here suggests that sugar-sweetened beverages may pose a unique health risk that cannot be attributed to sugars more generally. Even when diabetics were excluded, the risks associated with high sugar consumption overall were between 24 and 51 percent lower than the risk associated with high levels of sugar-sweetened beverage consumption.
Inoue-Choi M, Robien K, Mariani A, et al. Sugar-sweetened beverage intake and the risk of type I and type II endometrial cancer among postmenopausal women. Cancer Epidemiology, Biomarkers & Prevention (2013); 22(12): 2384–2394.