This type of cancer, associated with higher levels of estrogen, has previously been linked with increased levels of insulin in the body and with being overweight or obese. The new study, published in Cancer Epidemiology, Biomarkers & Prevention, showed that drinking sugar-sweetened beverages was linked to estrogen-dependent type I endometrial cancer, but not the less common estrogen-independent type II form.
The study followed over 23,000 women, asking them how frequently they consumed various foods and drinks over the last 12 months. The researchers were particularly interested in sugar-sweetened sodas like Coke and like 7-Up and non-carbonated sugary drinks like Hawaiian Punch and lemonade. Sugar-free drinks included both caffeinated and caffeine-free cola. The team also examined whether sweets and baked goods, and starchy foods, might be connected to endometrial (a type of uterine) cancer risk.
Women who drank the most sugar-sweetened drinks -- more than four servings per week -- had a 78% greater risk of developing estrogen-dependent type I endometrial cancer than women who drank none. Women who were older, had higher body mass index (BMI), a history of diabetes, later menopause and any type of estrogen therapy also had a greater risk of developing endometrial cancer.
This jibed with previous research. "Obese women tend to have higher levels of estrogens and insulin than women of normal weight," study author Maki Inoue-Choi said in a statement. "Increased levels of estrogens and insulin are established risk factors for endometrial cancer."
However, the connection between sugary drinks and estrogen-dependent endometrial cancer remained regardless of body weight. And sugary drinks were the key, not just any form of sugar. The researchers did not see a similar association between uterine cancer and other sugary items, such as baked goods, or starchy foods, which are converted into glucose in the body.
"One possibility is that sugar from whole foods comes with other nutrients, such as fiber," Inoue-Choi told NBCNews. "Sugar from beverages doesn't come with these nutrients." It is thought that these nutrients somehow mitigate the damage from the sugar.
"Research has documented the contribution of sugar-sweetened beverages to the obesity epidemic," said Inoue-Choi. "Too much added sugar can boost a person's overall calorie intake and may increase the risk of health conditions such as obesity, diabetes, heart disease, and cancer."
Endometrial cancer occurs in the cells that form the lining of the uterus. There are other types of uterine cancer, but endometrial is the most common, affecting about 50,000 women per year in the U.S. About 8,000 women die from it each year.
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