Obesity increases a person's risk of multiple cancers, including rectal cancer.
One of the factors leading to an increase in obesity is believed to be the use of high fructose corn syrup (HFCS) as a sweetener in soft drinks. Goncalves and others from Weill Cornell Medical College found that even in mouse tumor models that are not obese, intake of HFCS can promote the growth of bowel cancer. An enzyme (ketohexose kinase) in tumors can convert fructose into fructose-1-phosphate, thereby changing the metabolism of tumor cells and promoting cell growth.
Excessive consumption of beverages containing high fructose corn syrup (HFCS) can lead to obesity and increase the risk of colorectal cancer. Whether HFCS directly causes tumorigenesis is unclear.
Goncalves et al. studied the effect of daily oral HFCS on adenomatous polyposis (APC) mutant mice prone to intestinal tumors. Researchers found that in the absence of obesity and metabolic syndrome, the tumor size and tumor grade of mice receiving oral HFCS increased significantly.
In addition, the researchers also observed that high fructose corn syrup increased the concentration of fructose and glucose in the intestinal lumen, respectively, and tumors transport these two sugars. Inside the tumor, fructose is converted to fructose-1-phosphate, leading to the activation of glycolysis and an increase in fatty acid synthesis that supports tumor growth.
These mouse studies support the hypothesis that if you eat a diet that contains both glucose and fructose, even if the dose is moderate, it can enhance the occurrence of tumors. But it remains to be seen whether similar processes will occur in humans.