How Exercise Supports Cancer Prevention and Recovery

Rich Roll: Cancer. What do we know about the impact of exercise on cancer prevention?

Dr. Rhonda Patrick: Cancer prevention and treatment are important. We've talked a lot about cardiovascular disease, which is the leading cause of death in the United States and many developed nations. Cancer is the second leading cause of death. Exercise is one of the best things you can do for cancer prevention and treatment.

People who have been diagnosed with cancer may think they need to save their energy and rest. For many years, many oncologists advised against exercise because they didn't think patients could do it. But exercise causes many changes, including changes in inflammatory and immune cells.

Exercise can increase the number of immune cells that kill cancer cells, including cytotoxic T lymphocytes and natural killer cells. Cancer cells can take a long time to form a solid tumor. A cell divides from one cancer cell into two, four, eight, and more. Cancer cells are abnormal and stressed.

Chemotherapy is toxic and kills normal cells too, but it kills cancer cells because they are primed to die. They have acquired mutations that help them override programmed cell-death systems or evade the immune system. They need a stressor to push them over the edge, which a toxic chemotherapy drug can provide.

Exercise is also a stress on the body. It acutely increases inflammatory cytokines, followed by a beneficial adaptation with anti-inflammatory cytokines. The net effect is anti-inflammatory. Normal cells can produce antioxidants and anti-inflammatory cytokines as they adapt. Cancer cells cannot adapt in the same way, so exercise stress may contribute to their death.

Exercise can also make it more likely that the immune system finds a small number of cancer cells by increasing immune cells that can kill them. Cancer cells also have mechanoreceptors that sense movement. When exercise increases blood flow, circulating tumor cells experience shear stress. Normal cells can withstand this force, but cancer cells may be more vulnerable to it.

Studies in people with colorectal or breast cancer have associated exercise with a lower risk of recurrence and cancer mortality. Studies in those cancers have also shown fewer circulating tumor cells among people who exercise. Circulating tumor cells escape the primary tumor site and enter the blood to establish themselves elsewhere, which is metastasis. Reducing metastasis can improve outcomes.

Exercise supports cancer prevention in many ways. It changes immune function and improves metabolic health. Obesity is associated with 13 types of cancer, and factors such as glucose, insulin, and hormones are involved.

Rich Roll: These are not independent.

Dr. Rhonda Patrick: Exactly. They're all connected.

Rich Roll: What you said makes sense. I understand why it would help stave off cancer progression. But exercise-induced stress creates oxidation, and my layperson's brain thinks oxidation is bad for cells. Exercise also causes inflammation, which we think of as bad for health. There are differences between acute and chronic responses. Can you make that clearer?

Dr. Rhonda Patrick: Exercise is a type of hormetic stress, meaning a beneficial stress. It creates oxidation, reactive oxygen species, IL-6, pro-inflammatory cytokines, and acute inflammation. But our cells adapt by increasing antioxidant systems such as glutathione and superoxide dismutase. These systems address both the acute oxidation from exercise and inflammation generated during normal life in the days that follow. The net effect is anti-inflammatory and antioxidant.

Cancer cells do not have the same hormetic response. They don't increase antioxidant and anti-inflammatory genes in response to exercise because their regulatory systems are disrupted. That difference is part of the proposed mechanism.

Dr. Valter Longo, a mutual friend, has shown a related concept in a few studies. He calls it differential stress resistance and has studied it in the context of fasting. Fasting shortly before cancer treatment may stress cancer cells while normal cells increase antioxidant and anti-inflammatory responses. Deliberate heat exposure may cause a similar type of response.

When you enter a sauna, heat acutely creates reactive oxygen species and inflammation. IL-6 increases, but the longer-lasting response includes more IL-10, an anti-inflammatory cytokine. Several beneficial stressors can produce this pattern, including exercise, fasting, deliberate heat exposure, and plant phytochemicals.

Phytochemicals such as sulforaphane, resveratrol, and curcumin create a small amount of stress but strongly activate cellular stress-response pathways such as NRF2. That pathway increases a variety of anti-inflammatory and antioxidant genes. This beneficial type of stress, or eustress, is one thing exercise provides.

Rich Roll: Setting aside cancers of the blood, not all cancers are the same. Are some more resilient and others more responsive to exercise?

Dr. Rhonda Patrick: It does seem that some are. Breast and prostate cancers are hormone-related and closely connected to metabolism, so they are studied frequently in relation to exercise. Colorectal cancer has also been studied extensively and appears to respond well.

I don't know as much about other cancers, such as brain cancer. I would imagine exercise would be beneficial, but there is not enough data.

Rich Roll: Yeah.

Dr. Rhonda Patrick: That limits what we can show. Cancers are different. I would not call the effect a sure thing for every cancer, but I feel strongly that exercise is broadly beneficial and appears to help with most cancer types.