Colorectal cancer: A preventable widespread disease?

Trends and advances in cancer medicine

Colon cancer is one of the most common and deadly cancers. Thanks to improved screening, the number of affected individuals has been declining for years, but the incidence of colon cancer is increasing at an alarming rate, especially among younger people. The reason for this is not yet fully understood, but there is increasing evidence that our modern lifestyle is to blame.

But what factors specifically influence whether we develop colon cancer, and how do they interact? What type of cancer is it, and how does it develop? How is a tumor in the intestines detected, and how can it be treated? Researchers are discovering new answers to these questions and new aspects of colon cancer almost every week. An overview.

The bacteria in the intestinal flora can also be involved in tumor development. © ChrisChrisW_GettyImages

Between Lifestyle and Genes

How Do Colon Tumors Develop?

There are numerous risk factors that promote colon tumors. Many of these factors can be influenced by lifestyle. As with other types of cancer, these include obesity, alcohol consumption, smoking, and lack of exercise. "Statistically speaking, the likelihood of developing colon cancer can be reduced by 20 to 30 percent through physical activity," writes the German Cancer Aid.

Running away from the tumor?

However, you can also overdo it with exercise: A study recently presented at a conference found that young marathon runners have an above-average incidence of precancerous lesions in the colon. The team suspects that ultra-long runs increase the risk of cancer-causing mutations in colon cells. This is because prolonged physical exertion increases blood flow in the legs and reduces blood flow in the colon, causing cells to die or divide more rapidly in some places. This could lead to tumors, it is suspected. However, other lifestyle factors of long-distance runners could also be the cause.

"Lifestyle is key," emphasizes Robert Grützmann from the Colorectal Cancer Center at the University Hospital of Erlangen, also recommending exercise and sports. "I primarily advise my patients to do muscle-building exercises. This is generally good for their health, but also helps them better survive an illness. According to recent studies, fasting diets also contribute to a longer, healthier life."

Stay away from meat

Diet does indeed play a special role in colorectal cancer. For example, the consumption of highly processed foods such as convenience foods, sausages, fast food, and sports nutrition can negatively alter the intestinal flora due to the fats, sugar, and additives they contain, thus promoting colon tumors. The iron in red meat has also been shown to damage intestinal cells.

White meat from chicken—a supposedly healthier alternative to red meat—has also been linked to colon cancer. However, critics criticize the study's methodology, which did not take the preparation of the chicken into account (doi: 10.3390/nu17081370). Therefore, it is still unclear whether ingredients in white meat per se or substances in processed chicken products are carcinogenic.

Red and processed meat are among the risk factors for colon cancer.

Protective Foods

A diet rich in fiber and vitamins from fruits, vegetables, legumes, and whole grains, however, can protect against colon cancer. These foods speed up digestion and prevent harmful substances from staying in the intestines for a shorter time. They also promote intestinal microbes that produce anti-inflammatory substances.

Ingredients in nuts such as macadamia nuts, hazelnuts, and walnuts, as well as almonds and pistachios, also have a protective effect. These inhibit inflammation, stimulate detoxification mechanisms in healthy intestinal cells, and activate the suicide program of tumor cells. The calcium in milk and yogurt, in turn, binds harmful substances, protects the mucous membrane, changes the composition of the microbes living in the digestive tract, and thereby reduces the risk of cancer.

Bacteria as Cancer Drivers

These examples show that diet and other risk factors interact with the intestinal flora. In fact, dozens of bacteria are particularly common in people with colon cancer and may trigger the cancer, a study has shown. These microbes of the intestinal flora produce molecules in their metabolism that damage the genetic material and can therefore lead to cancer. "The results of our meta-analysis support a model according to which – possibly many different – ​​microbes contribute to or benefit from tumorigenesis," explains the research team.

Recently, researchers identified another intestinal inhabitant that increases the risk of colon cancer even in people under 50 years of age: certain strains of Escherichia coli. These bacteria are important for healthy digestion. However, some of them produce the toxin colibactin, which can alter the genetic material in the mucosal cells. Therefore, people who carry these bacteria in their intestines as children often have genetic mutations in their intestinal cells that can lead to cancer later in life – and earlier in life than mutations in intestinal cells that arise from other causes.

Influence of Genes

People with a family history of colon cancer also have an increased risk of developing it, even at a younger age. Doctors define this as people in whom one or more close relatives have had a colon tumor or numerous colon polyps. In these cases, there is often a genetic, inherited predisposition. "Three to five percent of all cases can be traced back to known genetic mutations that can be inherited and primarily cause colon cancer," explains the German Cancer Society.

Predispositions Increase the Risk

In addition, people with certain pre-existing digestive disorders have a higher risk of developing colon cancer. These include diabetics, patients with cystic fibrosis, or intestinal diseases such as ulcerative colitis or Crohn's disease. The latter are chronic inflammations of the intestinal mucosa triggered by an excessive immune response in the body. Researchers suspect that a specific protein, which is significantly more common in the intestines of these patients, triggers tumors (doi: 10.1002/cac2.70022).

There are many factors that contribute to the development of tumors in the intestine. But what exactly happens after cells in the intestine become cancer cells? And how can we determine what's happening in the intestine?