May 6 (UPI) -- Adults who drink two or more daily sugar-sweetened beverages may be doubling their risk for developing bowel cancer before they turn 50 years old, according to a study published Thursday by the journal Gut.
Moreover, each additional serving consumed daily is associated with a 16% higher risk for the disease, the data showed.
Because the study focused primarily on cancer risk in women, it is believed the findings highlight the potential dangers they face from sugary drink consumption, the researchers said.
"Our findings have added another reason to avoid sugar-sweetened beverages and also provided preliminary support that intake may contribute to the rising incidence of colorectal cancer under age 50, a growing concern in cancer prevention," study co-author Dr. Yin Cao told UPI in an email.
The findings "also suggest that reducing sugar-sweetened beverage intake and replacing [them] with other healthier beverages, in particular milk, would be a better and wiser choice for long-term health," said Cao, an associate professor of surgery at Washington University School of Medicine in St. Louis.
Heavy consumption of sugar-sweetened beverages already has been linked to increased risk for obesity and type 2 diabetes, a disease caused by the body's inability to process sugar.
Sugar-sweetened beverages, such as soft drinks, fruit-flavored drinks, and sports and energy drinks are the leading source of added sugar in U.S. diets, with 12% of the population consuming more than three servings -- 8 fluid ounces each -- daily, the researchers said.
At the same time, cases of bowel cancer diagnosed before age 50, called early onset colorectal cancer, have been increasing in the United States for nearly 20 years, they said.
Adults born around 1990 have a two-fold higher risk for colon cancer and a four-fold higher risk for rectal cancer than adults born around 1950, according to the researchers.
Given these parallel trends, they theorized that intake of these drinks also may have an association with bowel cancer, given that they are processed through the digestive tract.
To explore this potential relationship, Cao and her colleagues analyzed data from more than 95,000 participants in the Nurses' Health Study II, an ongoing monitoring study of 116,429 female registered nurses in the United States.
The women reported what they ate and drank by responding to food frequency questionnaires administered every fours years, starting in 1991.
In addition, more than 41,000 of them reported on what, and how much, they drank between ages 13 and 18.
Participants also supplied information on potentially influential factors, including family history of bowel cancer, lifestyle, regular use of aspirin or non-steroidal anti-inflammatory drugs and vitamin supplements, all of which have been linked with increased bowel cancer risk.
After the study tracked participants' health for an average of 24 years, 109 women developed bowel cancer before age 50.
Compared with those who drank fewer than one sugar-sweetened beverage serving per week, women who consumed two or more every day were more than twice as likely to be diagnosed with bowel cancer, the researchers said.
Among the participants who reported on their teen patterns of consumption, each daily serving was associated with a 32% higher risk for subsequently developing the disease before age 50.
Conversely, substituting sugar-sweetened drinks with artificially sweetened beverages, coffee or semi-skimmed or whole milk was associated with a 17% to 36% lower risk for early-onset bowel cancer.
The reasons for the relationship between sugar-sweetened beverages and cancer risk still need to be confirmed through further research, Cao said.
However, it is possible that the onset of obesity and type 2 diabetes linked with high intake plays a role in the development of cancer, she said.
These drinks may also negatively impact function of the human digestive system, which could promote the development of cancer, according to Cao.
"Higher sugar-sweetened beverage intake [is] associated with obesity, which has been previously linked to risk of early-onset colorectal cancer," Cao said.
"A recent experimental study also suggests that high-fructose corn syrup, the primary sweetener [in these drinks], may exert influence on colon tumor growth," she said.