Our Hidden Allies Within: How Gut Microbes Shape Our Health and Defend Against Cancer and Disease

In the hidden world within us, a strange and alien community thrives, forming what we know as the gut microbiota. These microscopic inhabitants play a monumental role in our health, particularly in the training and regulation of our immune system. From the moment we are born, our gut microbiota begins to colonize. It is this early life interaction with those microbes that helps our immune system learn to distinguish between harmless and harmful entities and encourages the maturation of our immune cells, ensuring that our immune system is well-equipped to protect us throughout our lives.

Beyond their role as teachers, when gut bacteria ferment the fibers provided to them via our diet, they produce a host of beneficial compounds including something called short-chain fatty acids. Our gut is technically considered to be outside of our body, I know, it is a strange concept, but think about it: It is part of a tube that goes from our mouth to our anus, both external openings. That means it is exposed to all sorts of things that would be harmful if they got into our circulation. Between our gut and the rest of our body stands the gut barrier. This barrier, made up of tightly joined epithelial cells, acts as a frontline defense against pathogens and toxins entering the bloodstream. And it is only a single layer deep. The short-chain fatty acids produced by our friendly colonizers are the preferred fuel for those cells and thus vital to maintaining this fragile barrier and our health.

When the barrier is breached, inflammatory agents can enter our bloodstream and potentially overwhelm our immune system, triggering systemic inflammation. This leaves us vulnerable to anything from metabolic disease, atherosclerosis, mental health issues, and cancer.

But keeping our gut barrier intact is not the only way short-chain fatty acids contribute to our health. They also play a role in reducing inflammation when it does occur. They function as signaling molecules that decrease the production of pro-inflammatory cytokines and enhance the production of anti-inflammatory ones. Short-chain fatty acids also promote the expansion of regulatory T-cells (T-reg). Those cells are a vital part of our immune system, acting as a sort of overseer to ensure our inflammatory response is balanced, preventing the overreactions we see in autoimmune disorders and allergies.

In addition to their role in immune modulation, gut bacteria engage in a form of competitive exclusion. They outcompete pathogenic microbes for nutrients and attachment sites, reducing the likelihood of infections. Some beneficial bacteria even produce antimicrobial compounds, further inhibiting the growth of harmful pathogens.

This dynamic relationship makes our gut microbiota a powerful ally in our fight against cancer. Especially cancers of the colon. By not only keeping inflammation in check but also modifying the tumor microenvironment and keeping out bacteria that fuel cancer growth, they not only help prevent the onset of cancer but also slow the progress of tumor development and spread.

Like any relationship, the one we have with our microbial companions requires nurture and care. The choices we make every day determine the quality of the environment they live in. If we want them to thrive, we need to provide them with the right fuel and living conditions.

First and foremost, there is of course diet. Because what we eat, they eat. Or to be more precise: what is left of what we eat. I am talking about fiber. Fiber is a type of carbohydrate our body can not digest, but our friendly colonizers can. It is by fermenting this fiber, that they produce those short-chain fatty acids. It is found in vegetables, grains, fruits, pulses, and nuts. Sticking to a mostly plant-based diet will already set you on the right path. Making sure you include some that are minimally cooked or raw will increase the amount of fiber available for our friends. There are estimated to be anywhere between 500 to 1000 different species of bacteria that call our gut their home and they each have their unique taste and preference for food. The more varied your diet, the more diverse your microbiota will be. While we are still a long way from understanding which role they each play, one thing that is agreed on is that microbial diversity is much more important than the specific strains making up your microbiota.

Having said that, we do know that an overabundance of bacteria belonging to certain phyla (families of related bacteria), like Firmicutes, can negatively affect our health. A large presence of Firmicutes is linked to obesity and metabolic disorders, as these bacteria can influence fat storage and energy extraction from food. Not what we want in our fight against cancer. Unlike most bacteria, Firmicutes seem to thrive on refined carbohydrates and they appear to be more abundant in people consuming a diet higher in animal protein. Now let me just state that they are not “bad” nor is the consumption of animal protein. It is the ratio that matters. You want to make sure you have enough bacteria belonging to other phyla such as the Bacteroidetes to keep your Firmicutes in check. And Bacteroidetes love their vegetables. The occasional indulgence in pizza or cheesecake is not going to hurt you (unless you are lactose intolerant), you just want to make sure this is not what your diet consists of most days.

A great way to introduce more bacteria to your gut is by consuming fermented foods. With one caveat: avoid those that have a high salt content such as traditional kimchi. Those are linked to an increased risk of colon cancer, the opposite of what we are after. Luckily there are many types of fermented foods available that use little to no salt. Even most kimchi available in health food shops is much lower in salt than the real thing. But it is expensive. Real yogurt, even plant-based ones, contains an abundance of beneficial bacteria, as does kefir, kombucha, and cheese (not counting supermarket cheese which is not made by fermentation).

Besides limiting foods that contribute to an imbalance of bacterial populations, you also want to take care not to indulge too often in dietary and lifestyle choices that will actively harm our fragile ecosystem. Things like fried foods, alcohol, nicotine, high use of NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) like Ibuprofen, and aspirin, antibiotics, and recreational drugs like cocaine are detrimental to our gut microbiome.

What we consume is not the only thing impacting our microbiome. Lifestyle factors such as getting enough sleep, managing stress, and adequate hydration are all contributing to our gut health.

Our circadian rhythms don’t just regulate our sleep-wake cycle, they govern the switching on and off of many of our genes throughout the 24-hour cycle. Ensuring the right proteins get made at the right time. Poor sleep or irregular sleep patterns can disrupt this delicate balance, affecting our microbiome and leading to a decrease in beneficial bacteria and an overgrowth of harmful microbes.

It is also important to manage stress as best as we can. Chronic high levels of cortisol, the stress hormone, can be deleterious to our microbiome. It can impact metabolic functions, including glucose regulation and fat storage which can affect which bacteria can thrive in our gut as well as lead to gastrointestinal issues such as constipation or diarrhea. These disruptions in gut motility can alter the transit time of food and waste through the digestive tract, impacting microbial growth and activity in the gut.

Another often overlooked factor contributing to a healthy gut is hydration. Remember that precious gut barrier? It is lined with a mucous membrane which plays an important role in our immune system. This mucus layer also provides a habitat for our microscopic support team. These microbes adhere to the mucus and thrive in this environment. Proper hydration is necessary to ensure that the mucous membranes are well-lubricated and functioning optimally.

Last but not least is the all-time superstar of lifestyle interventions: Exercise. Yes, even your gut microbes love it when you move. Exercise can selectively promote the growth of beneficial bacteria, especially those producing higher levels of short-chain fatty acid (SCFA). It also enhances gut motility, fostering a favorable environment for beneficial bacteria to thrive. Exercise can also influence the balance of hormones that interact with the gut microbiome, such as cortisol, serotonin, and endorphins. For example, regular physical activity can reduce cortisol and increase serotonin levels.

So put on your sneakers and make both yourself and your gut happy!

Of course, no lifestyle interventions, even the most perfect ones, never offer a guarantee that we will not get cancer. But they do stack the deck in our favour. Even if we do get sick, study after study shows that our chances of recovery and avoiding recurrence are hugely impacted by the choices we make. The way I always put it to my clients is, it is like training for a marathon. It may not guarantee you a smooth run or even a finish, a lot can happen on the day. But it for sure gives you a much better chance of crossing the finish line.

Sybille Hazward