How a High-Fiber Diet Can Improve Outcomes in Melanoma

You probably aren’t getting enough fiber. Studies suggest that just five percent of American adults meet the recommended amounts of 21-25 grams of fiber a day for women and 30-38 grams a day for men. While everything from apples to air-popped popcorn are great sources of dietary fiber, not getting enough increases your risk for obesity, strokes, heart disease, and certain types of gastrointestinal disorders. 

Fiber doesn’t just improve digestion. It also lowers your cancer risk. Now new research suggests it improves the effectiveness of melanoma treatment as well. Here’s what researchers learned. 

Skin Cancer Treatments

The result of genetically damaged cells dividing rather than dying, cancer can sometimes spread or metastasize. More people get skin cancer than any other form of the disease––which is understandable as the skin is our largest organ. Roughly 20% of the population will be diagnosed with the disease in their lifetime. The deadliest form of skin cancer—melanoma—is named for the cancer’s location. It happens when there is damage to the color-producing cells––the melanocytes. It often occurs in places that aren’t exposed to the sun, and unlike other versions of skin cancer, it affects people of color as well as Whites. Almost 200,000 people in the U.S. are diagnosed with melanoma each year. It has a 99% five-year survival rate –– so long as it doesn’t metastasize. Unfortunately, melanoma is extremely aggressive, quickly spreading to the lymph nodes, lungs, or brain.

Our bodies can conspire against us in the cancer fight. That’s because while our immune system is designed to fight foreign invaders, it’s usually prevented from attacking our own cells. This is generally a good thing. Autoimmune disorders like Type 1 diabetes and lupus occur when our immune system misidentifies part of our body as foreign and releases a flood of antibodies to fight it. A similar overreaction in the immune system occurs during a cytokine storm when our body is flooded with inflammatory proteins or cytokines. This overreaction has also been linked to numerous deaths from COVID-19.

Usually, a molecule called a “checkpoint” prevents T-cells from attacking our cells. They also stop them from fighting cancer cells. Immunotherapy uses drugs called “checkpoint inhibitors” to supercharge those T-cells, enlisting them in the cancer fight. This has been one of the most effective treatments for advanced melanoma. Unfortunately, it doesn’t always work. Researchers have been examining patient profiles in an effort to discover the role diet may play in outcomes. One recent study suggested that the fiber melanoma patients eat (or don’t eat) has an outsized role in whether or not their treatment is successful.

High-Fiber Diets and Immunotherapy

To see why some patients respond better to immunotherapy than others, researchers have looked at their gut microbiome––the community made up of over 10 trillion microbial cells belonging to over 1,000 different species of bacteria. Our gut microbiome is crucial to our overall health. Another recent study looked at the role of probiotics––the so-called “good bacteria” found in yogurts. The study found that certain bacteria connected with diets rich in probiotic foods improved outcomes for patients undergoing immunotherapy. Yet this new research contradicts that conclusion somewhat, finding that while a high-fiber diet is beneficial, probiotic supplements may do more harm than good. 

Conducted by the University of Texas and the National Institutes of Health, the study focused on immune checkpoint blockade (ICB) drugs. As one of the study’s authors, Andrey Morgun, explains, “ICB has been a game-changer in cancer therapy, and the influence of the gut microbiome on therapeutic response has been demonstrated in numerous studies, in preclinical models and also in research involving human cohorts. A person’s microbiome is shaped by a wide range of environmental factors including food and medications, while human genetics accounts for a much smaller proportion of the microbiome variation from person to person.”

Examining hundreds of melanoma patients, researchers focused mainly on those taking a type of ICB known as “anti-programmed cell death protein therapy.” They also looked at mice implanted with tumors. With people, they observed that those who ate a high-fiber diet were most likely to benefit from the drug––their cancer stopped spreading. The treatment was most successful on patients with high dietary fiber intake and no probiotic use. The mice had similar results. 

It’s very important to note that the study found best success among patients who reported no use of over-the-counter probiotic supplements. In other words, it didn’t recommend against dietary sources which in other studies have proven to be beneficial with cancer treatments and are an important component in good gut health. Patients on immunotherapy need to inform their doctors about probiotic supplements they are taking. Of course, oncologists should know about everything a patient takes because no matter how benign a vitamin pill or over-the-counter drug may seem, it can affect your treatment.

For everyone, however, the study reinforces the value of a high-fiber diet. It also doesn’t negate how important yogurt and other probiotic rich foods are to gut health––which lowers your risk of cancer.

References

• Closing America’s Fiber Intake Gap
• Chart of high-fiber foods
• Skin cancer: incidence rates
• What is the Difference Between Melanoma and Nonmelanoma Skin Cancer?
• Melanoma Overview
• The COVID-19 Cytokine Storm; What We Know So Far
• Immunotherapy for Melanoma
• Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response
• Associated Cancer Statistics