As rates of colorectal cancers increase among young people, a new study published in Gut suggests that consuming sugary drinks could be linked to an increased risk of colorectal cancer among women, Nicholas Bakalar writes for the New York Times.

Improve patient access to nutrition-reinforced diets

Study details

For the study, researchers examined the consumption of sugary drinks and cases of colorectal cancer among 94,464 female registered nurses. The nurses were part of a long-term prospective health study that took place between 1991 and 2015, which followed participants from ages 25 to 42. Researchers also looked at a subset of 41,272 nurses who reported their consumption of sugary drinks from ages 13 to 18.

The study examined the consumption of several different sugary drinks including soft drinks, sports drinks, and sweetened teas, as well as fruit juices such as apple and orange.

According to the Times, the researchers controlled for different factors that could potentially affect the risk of colon cancer, such as race, BMI, smoking, alcohol consumption, physical activity, and menopausal hormone use.

Key findings

Overall, the researchers found 109 cases of colorectal cancer among the women over an average of 24 years of follow-up. The researchers noted that while the absolute risk of colon cancer among younger populations remains small, the findings suggested that the relative risk for colon cancer was higher as consumption of sugary drinks increased.

Specifically, the researchers found that the relative risk of colorectal cancer more than doubled for participants who drank an average of two or more servings of sugary drinks a week compared to those who drank an average of less than one serving a week. Each additional serving of sugary drinks increased the relative risk by 16%.

Further, looking at sugary drink consumption during adolescence, researchers found that a serving a day was associated with a 32% higher risk of developing colorectal cancer.

According to the researchers, consuming fruit juice or artificially sweetened drinks was not associated with early-onset colorectal cancer. Additionally, researchers found that replacing a sugary drink with coffee or reduced fat milk was reduced the relative risk by 17% to 36%. However, no data on coffee mixed with sugar was recorded.

Discussion

Yin Cao, the senior author of the study and an associate professor of surgery at the Washington University School of Medicine in St. Louis, said while different conditions such as gut inflammation, insulin resistance, or high cholesterol may play a larger role in causing cancer in younger people than older people, the exact mechanisms behind these causes have not been identified yet.

"One hypothesis is that increased weight gain is causing the increase in risk, but we controlled for obesity," Cao said. "Still, it might be one of the things contributing. In studies in mice, high fructose corn syrup has been found to contribute to cancer risk independent of obesity."

She added, "This is the first time sugar-sweetened beverages have been linked to early-onset colorectal cancer, and this study still needs to be replicated. But researchers and clinicians should be aware of this largely ignored risk factor for cancer at younger ages. This is an opportunity to revisit policies about how sugar-sweetened beverages are marketed, and how we can help reduce consumption."

Separately, Nour Makarem, an assistant professor of epidemiology at the Columbia Mailman School of Public Health who was not involved in the study, said the findings show only correlation, not causation. They provide "robust evidence, novel evidence that higher intakes of soda are involved in a higher risk for colorectal cancer."

Makarem added, "We know that sugar-sweetened beverages have been linked to weight gain, glucose dysregulation, and so on, which are also risk factors. So there's a plausible mechanism that underlies these relationships." (Bakalar, New York Times, 7/5)