In light of suggestions linking the consumption of probiotics and the prevention of colorectal cancer, it is pertinent to evaluate the validity of such a connection.
General surgeon and surgical oncologist Dr. Grace Tan takes us through what research has pointed to, the important facets of colorectal cancer, and the role of probiotics in reducing the risk of this cancer.
According to the World Health Organization’s International Agency for Research on Cancer, “Colorectal cancer is the third most common cancer type worldwide; in 2020, almost 2 million cases were diagnosed. Colorectal cancer is the second most common cause of cancer death, leading to almost 1 million deaths per year.”1
With those statistics as a backdrop, the term colorectal cancer refers to the colon, rectum, or anus being affected by cancer. Colorectal cancer is a disease in which cells in the lower gastrointestinal tract (also called the large intestine) grow out of control and form a tumor.
This tumor has the ability to grow over time and affect the surrounding organs, with cancerous cells potentially spreading to other parts of the body via the body’s blood circulation.
Treatments aside; much of colorectal cancer prevention is focused on screening, a healthy lifestyle, and the role of one’s diet.
Understandably, when news of an ingredient which can be consumed readily to help prevent cancer is read, seen, or shared; that information carries a certain momentum in the context of cancer research and seeking better health.
However, much of what we know of the effects of probiotics both in preventing and treating colorectal cancer has yet to be examined by large-scale randomized studies.
At the same time, it is heartening that interest in this subject can firstly lead to a reminder of the preventive steps that one can take in the area of improving our lifestyles health-wise and considering undergoing screening for colorectal cancer.
Secondly, this interest can perhaps spur further research on the efficacy of using probiotics against the onset of colorectal cancer.
The United States’ National Center for Complementary and Integrative Health defines probiotics as “live microorganisms that are intended to have health benefits when consumed or applied to the body”2 and which “may contain a variety of microorganisms. The most common are bacteria that belong to groups called Lactobacillus and Bifidobacterium.”3
We can consume probiotics by eating food that has undergone fermentation or by taking supplements. For the former, we see the role of such fermentation where “cabbage becomes sauerkraut, cucumbers become pickles, soybeans turn into miso, and milk can be made into yogurt, cheeses, and sour cream.”4
In the case of supplements, these can be purchased easily for a variety of health purposes, a few of which are related to improving one’s immune system, addressing diarrhea, and achieving weight loss. It has been recommended that medical advice should prompt the use of such supplements. But we cannot deny the fact that these supplements are readily available. One should note that probiotic supplements are not seen as medication.
As an aside, a procedure that has garnered interest lately is a fecal transplant which is carried out to treat a bacterial infection of the Clostridium difficile bacterium in the lower intestine.5 This again uses bacteria which are beneficial for us.
The evidence from research is of good quality, suggesting that the consumption of probiotics can contribute to the prevention of colorectal cancer by exerting anti-cancer activity on the cells in the colon and rectum.6
In addition, patients with colorectal cancer have been shown to bear a distinct microbiota (collection of microorganisms) signature in their tumors and nearby tissue which may be altered with probiotics.7
However, most of the studies have involved animal models or a small number of human subjects. Larger clinical studies are needed for a better understanding of the properties and mechanisms of the action of probiotics in preventing colorectal cancer development.
Going back to Lactobacillus and Bifidobacterium, many of us locally might be familiar with the marketing of a beverage or two which has made reference to ingesting good bacteria to aid the health of our digestive systems.
The preventive approach in question is similar to what is alluded to in such branding in terms of employing the aid of specific bacteria to improve gut health.
As a topic of interest, the human microbiome which, according to a particular source, “is composed of communities of bacteria (and viruses and fungi) that have a greater complexity than the human genome itself”8 contains trillions of microbes, “the bulk of which live in our gut”9 and there has been much research and discussion on the link between these gut microbes and overall health.
While we wait upon what further research on preventing colorectal cancer with probiotics might bring, the risk factors for this disease can be addressed with monitoring one’s diet for healthy consumption. Reducing red meat and processed meat intake could help.
In addition, keeping active along with smoking cessation and being mindful of the increased associated risk with obesity are important. Health screening can also play a role in tracking one’s general health outlook.
Colorectal cancer symptoms do not usually show in the early stages and undergoing a colonoscopy is a reliable method to screen for this condition.
Recently, the adoption of Artificial Intelligence has been shown to increase the incidence of catching polyps on camera in a colonoscopy.10 Polyps can turn cancerous on the inside surfaces of the colon or rectum.
The treatment for colorectal cancer depends mostly on the stage of the cancer. Hence, accurate staging is the most important factor – this will usually include scans involving computerized tomography (CT), positron emission tomography (PET), or magnetic resonance imaging (MRI).
Based on these scans, a physician will then be able to come up with a treatment strategy and recommend the next suitable step in the cancer treatment, be it surgery, radiotherapy, or systemic therapy i.e. chemotherapy.
The treatment also will be affected by the symptoms that a patient may have. For example, if a patient is bleeding from the tumor or faces obstruction from the tumor, he may require emergency surgery to deal with the acute problem.
6 Ambalam P, Raman M, Purama RK, Doble M. Probiotics, prebiotics and colorectal cancer prevention. Best Pract Res Clin Gastroenterol. 2016 Feb;30(1):119-31. doi: 10.1016/j.bpg.2016.02.009. Epub 2016 Feb 19. PMID: 27048903.
7 Ohara T, Yoshino K, Kitajima M. Possibility of preventing colorectal carcinogenesis with probiotics. Hepatogastroenterology. 2010 Nov-Dec;57(104):1411-5. PMID: 21443095.