A spate of recent population-based studies seems to be spelling the end for sugary drinks, with studies linking soda to outcomes like diabetes and obesity and even increased risk of death. Now, a paper released Wednesday in Science adds impacts on colon tumors to the list of their sour side effects.
The authors from Weil Cornell’s Graduate School of Medical Sciences showed that a daily dose of high-fructose corn syrup, a sweetener used in many sodas and sweet drinks, caused colon tumors to grow larger and more aggressively in mice. The tumors seemed to be able to feed on the sweetened substance.
The study’s co-senior author Lewis Cantley, Ph.D., says that this tumor feeding behavior isn’t limited to high-fructose corn syrup. He believes it may extend to traditional sweeteners.
“Our studies strongly indicate that people with risk factors for colorectal cancer should avoid drinking any drinks with sugar in them, whether high-fructose corn syrup or cane sugar (sucrose) or honey or molasses, or apple juice or orange juice. Eat an apple, not apple juice,” he tells Inverse.
Cantley and his co-authors “mimicked sugar-sweetener beverage consumption” by giving mice a dose of high-fructose corn syrup that was “calorically equivalent to human consumption of less than 12 ounces of sugar sweetened beverage” per day. In the paper, the authors use the term “sugar sweetened beverages”, but what they were really testing was high-fructose corn syrup.
The mice were genetically altered to be predisposed to the growth of colorectal polyps, which in turn made them predisposed to develop intestinal tumors. This allowed the study to focus on comparing how the resulting tumors, which would inevitably grow, were different between mice that consumed the high-fructose corn syrup and those that didn’t.
By the end of the study, the mice who got the high-fructose corn syrup developed more “large” adenomas, defined as those bigger than 3 millimeters in diameter. Those mice also developed more “high-grade tumors” — the type that grow faster and spread more aggressively.
Cantley and his co-authors were able to offer an explanation for why tumors seemed to grow larger and more aggressive. In a series of follow-up experiments, they noticed that the liquid high-fructose corn syrup delivered extra fructose into the bodies of the mice, where it overwhelmed transporters in the intestines — specifically, one called GLUT5. Transporters are proteins in the cell membrane that move chemicals in and out of the cell.
GLUT5 has been implicated in human studies too: “The consumption of as little as 5g of fructose can lead to the saturation of GLUT5 in the small intestine (i.e., malabsorption), resulting in an increased concentration of fructose in the lumen of the colon (large intestine) of healthy humans,” the team writes.
In short, the tumor cells can suck fructose directly from the inside of the intestine after a mouse consumes a lot of high-fructose corn syrup. These cells make this extra sugar their preferred energy source and use that to thrive.
“Our paper does not just show a correlation between sugary drinks and colorectal cancer, but also explains the molecular mechanism by which the sugar drives growth of the cancer,” Cantley says.
This is just a mouse study, so the process could go down very differently in humans. High-fructose corn syrup is, for now, an FDA-approved food additive, though the study did prompt a defensive response from the American Beverage Association, which told CNBC “numerous studies have shown that the body treats HFCS and table sugar in exactly the same way.” Coca-Cola’s website, meanwhile, also notes that high-fructose corn syrup is not dangerous, instead emphasizing the risks of weight gain from high caloric intake.
Interestingly, this study also highlighted the effects of high-fructose corn syrup intake on colon tumors in mice that weren’t obese. Obesity is strongly associated with colon cancer, so this study can go a long way to decoupling the effects of sugar and the effects of additional weight on health going forward. Though this one mouse study probably won’t usher in the end of soda, it could be another nail in the coffin.
Abstract: Excessive consumption of beverages sweetened with high-fructose corn syrup (HFCS) is associated with obesity and with an increased risk of colorectal cancer. Whether HFCS contributes directly to tumorigenesis is unclear. We investigated the effects of daily oral administration of HFCS in adenomatous polyposis coli (APC) mutant mice, which are predisposed to develop intestinal tumors. The HFCS-treated mice showed a substantial increase in tumor size and tumor grade in the absence of obesity and metabolic syndrome. HFCS increased the concentrations of fructose and glucose in the intestinal lumen and serum, respectively, and the tumors transported both sugars. Within the tumors, fructose was converted to fructose-1-phosphate, leading to activation of glycolysis and increased synthesis of fatty acids that support tumor growth. These mouse studies support the hypothesis that the combination of dietary glucose and fructose, even at a moderate dose, can enhance tumorigenesis.