Drinking two or more sugar-sweetened beverages daily may raise the risk of dying from obesity-related cancers, new research shows.
The study, which included more than 900,000 participants, contributes to previous research suggesting that sugary beverages increase the risk of cancer and cancer-related mortality.
A more surprising finding is that consuming artificially sweetened beverages was linked to an increased risk of death from pancreatic cancer.
"This finding is very interesting," said Marjorie McCullough, ScD, RD, senior scientific director of epidemiology research at American Cancer Society. She noted that other studies that examined an association between artificially sweetened beverages and pancreatic cancer did not reveal a statistically significant association.
"Our study is the first, to our knowledge, that has found a statistically significant positive association, and it will be important to replicate this finding," said McCullough.
The study was published online in Cancer, Epidemiology, Biomarkers and Prevention.
In the study, McCullough and colleagues examined associations between drinking sugar-sweetened and artificially sweetened beverages and dying from any cancer or any obesity-related cancers. The researchers also examined this association for 20 individual cancer types.
Participants included 934,777 cancer-free adults from the Cancer Prevention Study–II (CPS-II) prospective cohort. At baseline, adults completed a questionnaire on their medical history, lifestyle exposures, and habits, including how many sugar-sweetened or artificially sweetened drinks they typically consumed each day.
Over a median 28-year follow-up, 135,093 participants died from cancer.
Overall, the researchers determined that consuming two or more sugar-sweetened beverages drinks daily (vs consuming none) was not associated with all-cancer mortality.
Regarding obesity-related cancers, McCullough and colleagues found a significant 5% increased risk of death from these cancer (hazard ratio [HR], 1.05); however, this association disappeared after controlling for body mass index (BMI). According to McCullough, this finding may signal that the association between sugary drinks and obesity-related cancer deaths is at least partly mediated by higher BMI, or excess body fat.
"Weight control is key to cancer prevention," noted Linda Van Horn, RD, chief of the nutrition division at the Feinberg School of Medicine, Northwestern University, Chicago, who wasn't involved in the study.
However, with regard to individual cancer’s, consuming two or more sugar-sweetened drinks each day was associated with an increased risk of dying from colorectal cancer (HR, 1.09) and kidney cancer (HR, 1.17) after adjusting for BMI.
Unexpectedly, sugary beverage intake was associated with a lower risk of esophageal and lung cancer mortality. This association held for lung cancer but not esophageal cancer after restricting the analysis to never-smoking participants (HR, 0.81; 95% CI, 0.70 – 0.94).
Artificial Sweetener and Pancreatic Cancer?
With respect to artificially sweetened drinks, consuming two or more beverages daily was associated with a 5% increased risk of death from obesity-related cancers (HR, 1.05), but that association became null after controlling for BMI.
However, the link to pancreatic cancer mortality remained after adjusting for BMI (HR, 1.11). This association should be studied further, the researchers said. They said there is a possibility that undiagnosed diabetes influenced the results.
"Continued research on the impact of both beverage types with cancer risk and mortality is warranted to determine whether these associations are causal or confounded by other lifestyle factors, and whether they are mediated through BMI," the researchers wrote.
Reached for comment, Marcus DaSilva Goncalves, MD, PhD, with Weill Cornell Medicine, New York City, noted that the association with colorectal cancer has been previously reported, and he agreed that these "findings strengthen the available evidence of an association between sugar-sweetened beverages and colorectal cancer mortality.
"Data from my lab in mice have shown that sugar-sweetened beverages deliver fructose directly to colon tumors, which stimulates the survival of cancer cells and growth of tumors," Goncalves said.
There are also recent clinical data suggesting that exposure to sugar-sweetened beverages during adolescence and adulthood promotes adenoma formation, the precursor to colorectal cancer, he said.
Regarding artificially sweetened beverage intake, Goncalves said the effect with pancreatic cancer is "surprising" and that he is not aware of other data, including data from several large studies, that support this relationship.
No specific funding for study has been reported. McCullough, Van Horn, and Goncalves have disclosed no relevant disclosures relationships.
