How Sugar Harms Your Gut and Increases Colorectal Cancer Risk

Follow the series "The Ultimate Guide to Kicking Sugar" here.

In this series, we explore the good and bad sugars and sweeteners, including popular natural ones, uncover the unexpected outcomes of cutting out sugar, and discover the ultimate way to do so.

Here’s a fact you may find hard to believe or might not want to accept: Sugar can damage our intestines and even increase the risk of colorectal cancer.

Sugar Increases the Risk of 2 Colonic Diseases

Inflammatory bowel disease (IBD) is widely regarded as the intestinal disorder most directly associated with sugar.

Crohn’s disease and ulcerative colitis are the two main types of inflammatory bowel diseases. These conditions can be highly debilitating, often leading to symptoms such as persistent diarrhea, abdominal pain, rectal bleeding, bloody stools, weight loss, and fatigue.

IBD has become increasingly prevalent in recent times.

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A narrative review published in Clinical Gastroenterology and Hepatology in 2022 highlighted that multiple epidemiological data indicate a direct correlation between the high consumption of sugar in Western diets and an increased risk of IBD.

The journal Inflammatory Bowel Diseases published a large-scale study that revealed, based on surveys of more than 366,000 adults from various European countries, that individuals who consumed the highest amounts of sugar and soft drinks had a 1.68 times higher incidence of ulcerative colitis compared to those who consumed the least. Moreover, another review showed that for every additional 10 grams of sugar consumed per day, the risk of Crohn's disease increased by approximately 1 percent.

Additionally, numerous population-based studies have indicated that about 10 percent of patients with IBD believe that consuming sugary foods can trigger disease flare-ups and worsen symptoms. The previously mentioned 2022 narrative review also pointed out that Crohn's disease patients often reported increased sugar consumption prior to feeling ill.

How Does Sugar Trigger Intestinal Inflammation?

Disrupts the Gut Microbiome

A high-sugar diet can lead to significant changes in gut microbial composition in a very short period. Bacteria that thrive on simple sugars multiply rapidly, whereas those dependent on fibers, such as Bacteroides, may decrease in number. Bacteroides are highly beneficial for both the human body and gut health, partly due to their ability to break down dietary fiber into short-chain fatty acids.

Short-chain fatty acids are essential for the gut, serving as vital nutrients for intestinal mucosal cells. They not only support the gut's immune and barrier functions but also stimulate gut repair, thus alleviating gut inflammation. In a high-sugar diet, short-chain fatty acids in the gut are rapidly depleted.

A decrease in the levels of short-chain fatty acids has been observed in the guts of patients with IBD.

A high-sugar diet can also lead to a reduction in the quantity of Akkermansia bacteria, beneficial microbes that regulate mucus layer thickness and support intestinal barrier function.

At the same time, sugar promotes the rapid growth of harmful bacteria.

An experiment published in Science Translational Medicine in 2020 revealed that sucrose-fed mice exhibited a significant increase in mucin-degrading bacteria in their intestines, resulting in the thinning of the intestinal mucus layer, aggravating colitis.

"It is direct evidence that eating sugar makes your body highly sensitive to developing colitis," Hasan Zaki, an assistant professor in the pathology department at the University of Texas Southwestern Medical Center, said during an interview with The Epoch Times. "All of this can happen within a few days."

A high-sugar diet also leads to an increase in the relative abundance of Proteobacteria in the gut. These bacteria carry toxic lipopolysaccharides, leading to inflammation and the impairment of intestinal epithelial integrity.

Sugar not only disrupts the balance of gut bacteria but also decreases overall microbial diversity. The production of short-chain fatty acids also relies on a diverse gut bacterial environment and the cooperation of different bacterial species.

Contributes to Leaky Gut

Sugar can lead to increased intestinal permeability, commonly referred to as "leaky gut."

It may also alter the architecture of the intestinal mucosa, leading to the thinning of the gut and the production of high levels of reactive oxygen species, ultimately causing damage.

Substances that shouldn't typically enter the body, such as bacterial lipopolysaccharides, entering the bloodstream from the gut can lead to endotoxemia, exacerbating both local and systemic chronic inflammation.

Additionally, the accumulation of sugar in the colon increases the intestinal osmotic load, which retains excess water in the intestines. This also accelerates the fermentation rate of gut microbiota, resulting in bloating, abdominal pain, and intestinal dysfunction.

Inhibits Gut Regeneration

The colon's regeneration rate is rapid, with intestinal stem cells continuously dividing while old cells are continually shed. However, a study published in 2023 revealed that a high-sugar diet can disrupt this mechanism. The study also found that sugar directly affects the proliferation of colonic epithelial cells, inhibiting their growth, and this damage intensifies with higher sugar concentrations.

Furthermore, a high-sugar diet can alter the colon's innate immune function and reduce the number of intestinal immune cells, diminishing their responsiveness to tissue damage.

Mr. Zaki emphasized the importance of recognizing the harm that sugar inflicts on the human body, stating: "We spend a lot of money to deal with those diseases, but that's not the solution.

"I think we should have some kind of policy from governments to make sure that we understand that sugar is harmful, just like smoking is harmful."

The Strong Connection Between Sugar and Colorectal Cancer

Sugar is also associated with the occurrence, recurrence, and mortality rates of colorectal cancer.

In a prospective cohort study involving stage three colon cancer patients, it was found that individuals who consumed two or more servings of sugar-sweetened beverages per day experienced a 67 percent increased risk of colon cancer recurrence or mortality compared to those who consumed less than two servings monthly. The risk increased even further, reaching 122 percent, for patients who were both overweight and less physically active.

An older case-control study conducted by University of Utah researchers revealed that both high sugar intake and a high glycemic index diet increase the risk of developing colon cancer by more than 50 percent.

"Consuming large amounts of sugar leads to an increase in stored energy in the form of fat, indirectly raising the risk of colon cancer," said Dr. Jeremy Kortmansky, associate professor of clinical medicine (medical oncology) at Yale School of Medicine, chief network officer at Smilow Cancer Hospital, and clinical director of the gastrointestinal medical oncology division at Yale Cancer Center, during an interview with The Epoch Times.

The indirect connection between sugar consumption, obesity, and cancer can be explained in several ways. According to Dr. Kortmansky, one particularly compelling theory involves the relationship between obesity and insulin resistance. Obese individuals often have higher insulin levels, which can stimulate cancer's insulin-like growth factor receptors, thus activating pathways that promote cancer development and growth. This interferes with intestinal cell growth and division, resulting in abnormal cell renewal in which old cells fail to die off.

As for the theory suggesting that sugar-induced inflammation increases the risk of cancer, Dr. Kortmansky explained that inflammation in the body often leads to local damage and DNA changes in cells. Normally, inflammation would cause these problematic cells to die, but if they survive, there's a potential risk of cancer development.

Additionally, there are some studies that establish a direct connection between sugar and cancer.

An animal study published in Nature in 2019 confirmed that high-fructose corn syrup directly promotes the growth and progression of colorectal cancer tumors, and this effect is independent of obesity. Lewis Cantley, the lead researcher of the study and a professor at Harvard Medical School's Department of Cell Biology, emphasized during an interview with The Epoch Times that this effect might also apply to humans.

"Consumption of high-fructose corn syrup dramatically increased in the 1960s. Over the following 20 years, there was a dramatic increase in colorectal cancer in relatively young adults," he pointed out, noting that such people typically have KRAS mutations. KRAS mutations are oncogenes with the highest mutation rate among cancers and are linked to cancers with high mortality rates.

"We showed that giving mice high-fructose corn syrup orally had the same effect of enhancing colorectal cancers in the context of KRAS mutations."

Just 5 to 25 grams of fructose can saturate the absorption capacity of the small intestine, after which fructose enters and comes into direct contact with the colonic lumen of the proximal colon.

In a clinical preliminary study published in The American Journal of Clinical Nutrition in 2022, an analysis of lesion location was conducted on 2,733 cases of colorectal cancer deaths. The results revealed direct associations between high consumption of sugar-sweetened beverages and total fructose intake and an increased incidence and mortality rate of proximal colon cancer.

Interestingly, this significant relationship didn't exist in the distal colon or rectum. Researchers believe that these findings provide evidence that dietary sugar can directly contribute to the development of colorectal cancer.

Next: A deeper look at how sugar can feed cancer.

Read the entire "The Ultimate Guide to Kicking Sugar" series here.