Growing volume of empirical evidence suggests a strong link between consuming sugary drinks, obesity and increased risk of colorectal cancer. Now researchers at Baylor University in the US have shown that consuming a daily modest amount of high-fructose corn syrup — the equivalent of people drinking about 360ml of sugar-sweetened beverage daily — accelerates the growth of intestinal tumors in mouse models of the disease, independent of obesity.
The current view is that sugar is harmful to our health mainly because consuming too much can lead to obesity. We know that obesity increases the risk of many types of cancer including colorectal cancer; however, it was not clear whether a direct and causal link existed between sugar consumption and cancer. The researchers set out to address this important question. The team generated a mouse model of early-stage colon cancer where a specific gene —the APC gene that acts as gatekeeper in colorectal cancer — is deleted. Without the APC gene, normal intestinal cells neither stop growing nor die, forming early stage tumors called polyps.
More than 90 percent of colorectal cancer patients have this type of APC mutation. Using this mouse model of the disease, the team tested the effect of consuming sugar-sweetened water on tumor development. The sweetened water was 25 percent high fructose corn syrup, which is the main sweetener of sugary drinks people consume. High-fructose corn syrup consists of glucose and fructose at a 45:55 ratio.
When the researchers provided the sugary drink in the water bottle for the APCmodel mice to drink at their will, mice rapidly gained weight in a month. To prevent the mice from being obese and to mimic humans’ daily consumption of one can of soda, the researchers gave the mice a moderate amount of sugary water orally with a special syringe once a day. After two months, the APC-model mice receiving sugary water did not become obese, but developed tumors that were larger and of higher-grade than those in model mice treated with regular water.
The results suggest that when the animals have early stage of tumors in the intestines, consuming even modest amounts of high-fructose corn syrup in liquid form can boost tumor growth and progression independently of obesity. Further studies on the mice revealed that colorectal cancers utilize high-fructose corn syrup, which is the ingredient in most sugary sodas and many other processed foods, as a fuel to increase rates of tumor growth.