Researchers have acknowledged that obesity increases the risk of cancer, and some studies even consider the existence of a causal relationship between this metabolic condition and cancer.
One important factor that can lead to obesity is the high intake of sugar through the frequent consumption of processed foods and sugary beverages.
However, so far, there has been limited research looking at the effects of sugar on tumor growth independently.
Now, a team of specialists from Baylor College of Medicine in Houston, TX and Weill Cornell Medicine in New York City, NY has collaborated with colleagues from other research institutions to identify a clear link between sugary drinks and the accelerated growth of tumors in colorectal cancer.
In the new study, the research team studied the effects of high-fructose corn syrup in mouse models of colorectal cancer.
The team opted for a solution of 25-percent high-fructose corn syrup because this is the type of sweetener that manufacturers most commonly use as an ingredient in popular soft drinks.
“An increasing number of observational studies have raised awareness of the association between consuming sugary drinks, obesity, and the risk of colorectal cancer,” explains co-author Jihye Yun, who is an assistant professor of molecular and human genetics at Baylor College of Medicine.
“The current thought is that sugar is harmful to our health mainly because consuming too much can lead to obesity,” she continues. “We know that obesity increases the risk of many types of cancer, including colorectal cancer; however, we were uncertain whether a direct and causal link existed between sugar consumption and cancer.”
Sugars in the gut and blood ‘feed’ tumors
By working on mouse models, the scientists aimed not only to confirm the link between dietary sugars and tumor progression but also to learn more about the mechanism at play.
The team conducted the research in mice with early-stage colorectal cancer in which they deleted a gene called “Apc.” This gene encodes a protein with the same name, and its deletion simulated a mutation that characterizes fast-growing colon cancer in humans.
“APC is a gatekeeper in colorectal cancer.
Deleting this protein is like removing the breaks of a car. Without it, normal intestinal cells neither stop growing nor die, forming early-stage tumors called polyps,” Yun explains.
“More than 90 percent of colorectal cancer patients have this type of Apc mutation,” the researcher points out.
In the first stage of the study, the researchers allowed the mice to drink the sugary beverage freely. As a result, the rodents put on a lot of weight within just 1 month.
To determine whether or not the corn syrup would boost cancer growth independently of obesity, the team then decided to administer the sugary drink in a way that would allow the mice to ingest it without putting on weight. So, the researchers gave the mice the sugary drink orally through a specially designed syringe once a day for 2 months.
Following this 2-month intervention, the investigators observed that the rodents had not put on too much weight, but they had indeed developed larger, more advanced tumors than the rodents who had only received water.
“These results suggest that when the animals have early stage of tumors in the intestines — which can occur in many young adult humans by chance and without notice — consuming even modest amounts of high-fructose corn syrup in liquid form can boost tumor growth and progression independently of obesity,” Yun points out.
“Further research is needed to translate these discovery to people,” she admits, though she goes on to add that, “however, our findings in animal models suggest that chronic consumption of sugary drinks can shorten the time it takes cancer to develop.”
“In humans, it usually takes 20 to 30 years for colorectal cancer to grow from early-stage benign tumors to aggressive cancers,” says Yun.