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A Gutsy Approach to Preventing Gastrointestinal Cancer
June 11, 2024
As a child, I used to play outside under the sweltering sun for hours. When I returned home tired, my mother would give me a glass of chilled buttermilk flavored with crushed ginger and tempered with curry leaves and mustard seeds. During the hot and humid months, curd rice with a simple side of stir-fried vegetables was also a staple. My grandmother and mother said it would keep the body cool and stomach free from illnesses. Such traditional remedies, which our elders swore by, are making a comeback, with several being scientifically tested, creating new ways to prevent and treat diseases.
At the intersection of science and tradition lies the significant importance of the gut microbiome or the collection of microorganisms that live naturally within the digestive system. Benefits provided by curd, buttermilk, or any other type of fermented food, such as kimchi or natto, go beyond merely keeping the stomach healthy as they boost the health of the gut microbiome. Now, a growing body of evidence suggests a healthy gut microbiome may help with the prevention and treatment of gastrointestinal cancers.
The gut microbiome and its functions
Within the gut of every person lies an ecosystem with diverse flora and fauna that could rival that of the Amazon rainforest. It contains trillions of microorganisms, such as bacteria, viruses, protozoa, and fungi. There are generally between 300 to 500 different species of bacteria present in the gut which outnumber human cells by 10 to one.
As soon as we are born, these species are present in the gut and vary in bacterial type and diversity depending on our birth (vaginal or caesarian), with children born vaginally showing better immunity as compared to children born via caesarian or C-section. The type of food a newborn consumes, whether breastmilk or formula, also helps to define the variety of microbiota. Furthermore, other factors that influence the microbiome include genetic makeup, sex, age, body mass index, and diet.
Importantly, the gut microbiome has several functions in our bodies. First, it trains the body’s immune system to differentiate between harmless and harmful microorganisms, as the gut contains almost 80% of the total immune cells in the body. The microbiome breaks down complex carbohydrates and fibre, and provides enzymes necessary for the synthesis of several vitamins such as B1, B9, and K12. As a byproduct of this process, the gut microbiome also produces short-chain fatty acids, which are essential to the body to run properly. Furthermore, it metabolizes bile in the intestines and sends it back to the liver to be reabsorbed and recycled, ensuring that the liver has adequate levels of bile.
Link between gut microbiome and gastrointestinal cancers
Gastrointestinal cancers are a set of heterogeneous cancers that affect the digestive tract including stomach, colorectal, liver, pancreatic, and esophageal. An estimated 4.8 million people—one in four cancer patients—are diagnosed with one of these cancers worldwide every year. They are responsible for one in three deaths due to cancer, taking the lives of 3.4 million people globally every year.
Even though genetic and lifestyle factors are the predominant cause of cancer, 20% of the cases are caused by microorganisms such as hepatitis B and C viruses, human papillomavirus, and Helicobacter pylori (H. pylori). Several studies have found that the gut microbiome and its products can promote or inhibit the progression of certain cancers. It can also influence different treatment modalities. As such, understanding the gut microbiome, its functions, and how to keep it healthy may be one way to prevent gastrointestinal cancers.
Studies have found that dysbiosis—an imbalance in the gut microbiota—can cause inflammation, resulting in cancer. In the case of stomach cancer, one of the risk factors is a persistent H. pylori infection, which can affect the acidity of the stomach and modify the gastric microbiome. Studies have also found that changes in the gastric microbiome can hasten the development of stomach cancer. Changes in the gut microbiota or lesser diversity of microbiota in the esophagus can lead to lesions, resulting in esophageal cancer. A leaky gut due to inflammation, an injury or dysbiosis contributes to the progression of liver cancer. Similarly, dysbiosis is also associated with the progression and survival outcomes of pancreatic cancer. Changes in the gut microbiome along with an unhealthy diet and alcohol consumption also contribute significantly to colorectal cancer, which is the second leading cause of cancer deaths worldwide.
The gut microbiome is capable of modulating the efficiency of anticancer treatments. Modified gut microbiota can reduce the efficiency of chemotherapy drugs or immune checkpoint inhibitors. However, introducing new species of bacteria through supplementation can improve the responses. Furthermore, a healthy microbiome can enhance the efficiency of immunotherapy. A study conducted in 2023 found that healthy gut bacteria can travel to lymph nodes and help fight cancers affecting other parts of the body too.
Keeping the gut healthy
Maintaining a healthy gut microbiome can not only prevent gastrointestinal cancers but also keep several other conditions such as Type 2 diabetes and cardiovascular diseases at bay. Some ways to keep the gut healthy include lowering stress through activities such as meditation or yoga, getting adequate sleep, consuming a healthy diet, eating slowly, and drinking adequate water.
The Mediterranean diet, which consists of fruits, vegetables, whole grains, legumes, nuts and seeds, and heart-healthy fats, can also help. Fibrous foods, garlic, and fermented foods rich in probiotics—yogurt, buttermilk, kimchi, miso, sauerkraut, natto, kombucha, and kefir—can boost the health of the gut microbiome. This also aligns with traditional remedies which place a greater emphasis on such foods to solve many gut-related problems.
The relationship between gut microbiome and gastrointestinal cancers is an exciting field, but researchers have only just started scratching the surface. As health communicators, we play a crucial role in bridging the gap between conventional practices and newer clinical insights. By disseminating accurate information, creating engaging content, and addressing misconceptions, we can enhance the understanding of how these options can support gut health. After all, a healthy gut could be all it takes to prevent cancer.
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