Sugar-Sweetened Drinks May Increase Bowel Cancer Risk, Study Finds

Sugar-sweetened beverages like soft drinks, sports and energy drinks, and fruit-flavored drinks may double the risk of bowel cancer before age 50 for women, according to research published in the journal Gut.

Researchers looked at data provided by over 95,000 participants in the Nurses’ Health Study II, an ongoing study of women that began in 1989 and tracks daily habits and health outcomes.

Participants provided food frequency information every four years, including how much they ate and drank during their adolescence. They also supplied data on family history of cancer, which helped researchers control for genetic factors. 

Researchers found that over a 24-year period, women with a higher intake of sugar-sweetened drinks were at significantly increased risk of developing bowel cancer, especially before age 50. Women who drank two or more per day were about twice as likely to be diagnosed with this type of cancer, and each daily serving was associated with a 16 percent higher risk.

Switching to artificially sweetened beverages had the opposite effect, with a 17%–36% lower risk of a bowel cancer diagnosis.

The Sugar-Cancer Connection

Although researchers emphasized that the exact reason is unknown, they suggested that the mechanism is likely the way sugar-sweetened drinks can cause a rapid rise in blood glucose and insulin secretion.

This can cause chronic, systemic inflammation and contribute to obesity, which are both associated with higher risk of bowel cancer development.

They added that emerging evidence also suggests that fructose—a type of simple sugar that makes up about half of table sugar—can impair gut function to some degree, particularly in terms of gut permeability, which may promote cancer development.

This is not the first time that a link between sugary drinks and cancer has been investigated. A study in BMJ found notable associations with these beverages and overall cancer, particularly breast cancer. Like the recent research, artificially sweetened beverages were not associated with these types of risks.

Research Caveats

An important note with the recent study is that it shows correlation, not necessarily causation, according to dietitian Leah Forristall, RD, LDN, of Simply Nutrition. That means it’s tough to say that sugar-sweetened beverages were the cause of the bowel cancer cases among participants, only that these drinks appeared to raise their risk of developing the condition.

“What we don’t know are factors like what additional foods were consumed at the same time as the sugar-sweetened beverages,” she says. “When we look at additional research, it is evident that foods consumed in combination with sugar affect digestion and blood sugar levels. Could this also have impact on the onset of something like bowel cancer? We don’t know.”

Other information could also play a role, like time of day for drinking these beverages, whether the results would be the same for men, and whether sugary drinks tended to lower consumption of nutrient-dense foods like vegetables.

Apart from those unknowns, there is some standard nutritional advice that can help those wondering how to have sugar-sweetened drinks in a way that presents fewer health risks.

“When thinking about typical nutrition recommendations in regard to sugar, it is almost always recommended to consume sugar with additional food groups,” says Forristall. “Fiber, protein, and fat will all help to stabilize blood sugar.”

What About Sports Drinks?

Although the study puts sugar-sweetened sports drinks in the same category as sodas, these type of beverages do have some benefits for those who are exercising with intensity, according to dietitian Kelsey Pezzuti, RD, who specializes in sports nutrition.

“Sports drinks are beneficial in certain situations, like exercising at moderate to high intensity for more than an hour,” she says. “They are ideal for athletes training several hours per day, such as marathon runners or triathletes.”

That’s because unlike soda, these drinks include electrolytes that can help prevent dehydration and assist in maintaining fluid balance, Pezzuti adds. The carbs they contain break down into glucose, which provides energy for endurance exercise.

“Many popular sports drinks are nothing but sugar, which is okay when you need sustained energy,” she says. “However, drinking too many added sugars is less ideal for your regular gym goer. One 20-ounce bottle of sports drink contains about eight teaspoons of added sugar, which is way more than most people should have in a beverage.”

If you’re exercising for less than an hour, going at a low-to-moderate intensity, or just looking for an everyday hydration option, she suggests plain water is a better choice.

“Replacing sports drinks with water will still help you power through workouts without the added sugar or calories," she says.