How Stress Can Lead to Cancer

Stress harms gut microbes that can slow tumor growth.

“It’s not the strongest of a species that survive, nor the most intelligent, but the ones most resilient and responsive to change.”—Charles Darwin

The continuous stresses of modern life surround us like a dense fog. Stress seems to be everywhere, all the time, unlike the rare and momentary stressors of our hunter-gatherer ancestors. Evolution crafted our stress response to last for a few minutes while running from a tiger. For better or worse, that kind of stress is over quickly.

Continuous stress is a modern malady that our bodies are unprepared for. It can lead to anxiety, neurosis, and depression. It can come in the form of a nasty boss, bloviating politicians, or existential climate change. And those are just the external stressors.

We also have internal stressors, including anxiety, poor health, and bad habits. The sum of our stressors is oppressive, but there is an even bleaker consequence: Stress can contribute to cancer.

A new study by Dr. Qing Li and her colleagues from Sichuan University found that stressed mice had reduced amounts of Lactobacillus bacteria. Lactobacillus is known to amp up the immune cells that target tumors. As a consequence of their loss, colonic tumors develop faster. In this way, Dr. Li found that stress can increase the odds of colon cancer.

This comports with a previous study this year from Yatrik Shah at the University of Michigan, which also found that stress reduces Lactobacillus and enhances colon tumor growth. In both studies, adding Lactobacillus as a supplement slowed the progression of the tumors.

Both studies were done in mice; much work is needed before human therapies are available. But there are some known techniques to improve your gut microbiome, and you can’t go wrong by following these three major guidelines.

Diet

We can’t change external stressors, but we have a surprising amount of control over our internal turbulence. Diet is an easy road to stress resilience. When you feed your good microbes, they produce substances called small-chain fatty acids that nourish and heal the cells lining the gut. That helps your gut fight off bad microbes, lowering inflammation. It also nurtures the Lactobacillus species that encourage your immune system to halt the growth of tumors. "Restoring beneficial bacteria in the gut, such as Lactobacillus, could strengthen the body's natural defenses against colorectal cancer," says Dr Li.

What kind of food do your beneficial microbes want? Fiber. This is a component of plants that gives them stiffness. Fiber is typically made with long chains of sugar molecules, and you can find it in veggies like onions, beans, and artichokes. Once again, your mom was right. Eat your veggies.

Polyphenols are also key to the health of your gut, and you can find them in foods like nuts, red grapes, and chocolate. Also eat fruits with both fiber and polyphenols like strawberries, blueberries, and raspberries.

Meat has no fiber, so although it is rich in nutrients, very few of them make it to the colon where the microbiome hangs out. "More plants, less meat" is a good mantra for stress control.

Exercise

Exercise increases your endorphins and makes you feel better. This attitude adjustment is a good antidote to stress. It doesn’t need to be strenuous either. Swimming, playing tennis, or a hike in the woods can do wonders to ease your mind. Exercise also helps to balance your gut microbes, keeping your gut lining robust against inflammatory pathogens.

If your main form of exercise is lifting the remote control, start slowly. You risk injury if you rush it, and recovery time can destroy a good exercise program.

Do something that you enjoy. If you’re lucky, you’ll be doing this for the rest of your life. Dancing, sports, or gardening are great exercises that can add some joy to the sweat. Get your friends to join in. The camaraderie makes it more fun, and a friend network makes you more serious about showing up.

Attitude

Hans Selye was known as the father of stress research, positing that “It’s not stress that kills us; it is our reaction to it.” That means our attitudes count when it comes to coping with stress.

It shouldn’t surprise us: The gut-brain axis is a two-way street, and the brain can affect our gut microbes in many ways. Studies have shown that cognitive behavioral therapy and meditation can improve your microbiome.

Your attitude is merely a habit you’ve established. We tend to identify ourselves by these habits, but we shouldn’t. We aren’t insects with specialized goals and a limited repertoire. We are complex creatures that can change in a flash—if we want to.

This sounds almost inane, but try smiling. Your friends and colleagues will smile back. It’s contagious, and the pressure of the entire world diminishes ever so slightly.

Try to stay calm. Nervous agitation is not a helpful problem-solving framework. All of these guidelines, if followed together, add up. With a good diet and frequent exercise, it is much easier to moderate your emotions—and turn stress into a challenge that you can conquer.

As Dr. Li puts it, "When people are diagnosed with a malignant disease like colorectal cancer, it's natural for them to experience feelings of worry and concern. However, these emotions are not beneficial for their condition. Our findings suggest that patients should try to adjust their mindset as much as possible to avoid further exacerbation of their disease."

If you keep your gut in good shape, your odds of getting colon cancer are reduced. That is a pretty good reward for a little exercise, a better diet, and a few extra smiles.

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References

Li, Q. & Yang, J. Chronic stress accelerated colorectal cancer progression by disturbing the balance of gut microbiota. Presented at UEG Week 2024; 13 October 2024; Vienna, Austria.

McCollum, Shannon E., and Yatrik M. Shah. “Stressing Out Cancer: Chronic Stress Induces Dysbiosis and Enhances Colon Cancer Growth.” Cancer Research 84, no. 5 (March 4, 2024): 645–47.