Study: High-Fiber Diet May Help Some Melanoma Patients

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Key Takeaways

  • Research has shown that a high-fiber diet contributes to a healthy gut and immune system.
  • A new study has found that patients with melanoma who are receiving immunotherapy to treat their cancer may have a better response to treatment if they eat a high-fiber diet.
  • Most people benefit from a diet that includes many plant-based whole foods, even if they do not have cancer.

New research from The University of Texas MD Anderson Cancer Center has found that people who are receiving immunotherapy for melanoma skin cancer may have better outcomes if they eat a high-fiber diet that's made up of mostly plant-based foods.

The findings were in line with those from previous studies that had shown having a healthy balance of certain gut bacteria improves the immune responses of people with melanoma.

What the Study Found

For the new study, the researchers looked at gut bacteria from 438 melanoma patients. Most of the patients had late-stage cancer and were getting systemic cancer therapy. All of the patients were having their tumor response and survival kept track of.

Of the patients in the study, 128 provided data on their dietary habits and were being treated with immune checkpoint inhibitors.

The researchers put the patients into two groups: One group ate a sufficient amount of fiber (at least 20 grams per day), and the other group ate less than 20 grams of fiber per day. Their fiber intake came from fruits, vegetables, whole grains, and legumes.

Patients who did not eat enough fiber had shorter progression-free survival rates than the patients who did eat enough fiber daily. For every 5-gram increase in daily fiber consumption, the patients had a 30% decreased risk of melanoma progression or death.

The researchers also looked at whether taking certain kinds of supplements that may benefit the gut microbiome would have any effect on patient outcomes. They concluded that taking probiotic supplements did not improve outcomes for patients in the study.

What Is the Gut Microbiome?

The gut microbiome refers to all the different microbes that live in our intestinal tract. They play a major role in digestion, immunity, and inflammation. Recent studies have shown that our gut microbiome may even affect our heart health.

Jennifer Wargo, MD

A healthy balance of bacteria in the gut can change and enhance our immunity.

— Jennifer Wargo, MD

Jennifer Wargo, MD, MMSc, director of the Innovative Microbiome and Translational Research program at The University of Texas MD Anderson Cancer Center, told Verywell that having a balanced gut microbiome goes hand-in-hand with having a strong immune system.

“Within our bodies, we have trillions of microbes that outnumber our cells, and a lot of them sit in our gut," said Wargo. "You have the gut microbiome, and on the other side, you have immune cells. A healthy balance of bacteria in the gut can change and enhance our immunity.”

Here's an example of what that could mean for your health: Some studies have suggested that taking antibiotics before getting a flu shot can decrease your immune response to the vaccine.

Sharing "Good" Microbes

A fecal transplant is a procedure where stool with a good balance of bacteria from a healthy donor is transferred to a person who is having treatment.

Wargo said that these transplants may help patients with melanoma achieve better treatment outcomes.

Another example applies to people undergoing cancer treatment. Immunotherapy treatments for cancer help a patient’s immune system fight the cancer cells.

For patients with cancer who are undergoing immunotherapy, a healthy digestive system supports a stronger immune system, which could lead to a better response to treatment. According to Wargo, gut microbes could also affect a cancer patient's response to chemotherapy and radiation.

Fiber and Gut Health

Fiber is food for the bacteria in your gut. The more fiber you eat, the healthier, more diverse, and more active your microbiome will be.

Carrie Daniel-MacDougall, PhD, MPH, associate professor of epidemiology at The University of Texas MD Anderson Cancer Center, told Verywell that many of the foods your gut microbes like are good for your body in general.

Jennifer Wargo, MD

Your diet and what you put into your body matters.

— Jennifer Wargo, MD

“These are same healthy foods encouraged across national dietary recommendations and by targeted organizations such as the American Institute for Cancer Research (AICR) that define diet and lifestyle recommendations across the cancer continuum from prevention to survival," said Daniel-MacDougall.

There are also some things that you may put in your body that can deplete your gut microbes. For example, while antibiotics have a place in treating various health conditions, research has shown that using them indiscriminately can affect the balance of gut bacteria.

Therefore, Wargo warned against the overuse of antibiotics, as it has the potential to do long-term harm to the microbiome and immune system.

Finding the Best Diet for Each Patient

Each person living with cancer has different needs. In the same way that one treatment may not work for everyone, the dietary needs of each person will be different, too.

“Cancer patients may have other concurrent conditions or medications that may require special guidance," said Daniel-MacDougall "And discussion with a clinical nutrition specialist and care/treatment team. Following a high fiber diet should also be done in the context of an adequate balance of protein and other important nutrients for the immune system and recovery, such as B12 and iron.”

Wargo said that people being treated for cancer "shouldn’t take matters into their own hands" when it comes to making decisions about their diet. In some cases, a patient may not be able to follow a high-fiber diet safely.

Luckily, most cancer treatment teams include a registered dietician, who can help patients figure out which diet will be the best fit for them.

Should You Take Fiber or Probiotic Supplements?

For people who want (and safely can) increase their fiber, there are ways to do so besides eating more fiber-rich foods, mostly in the form of supplements.

However, fiber from whole foods provides broader benefits than you'd get from the fiber that's found in supplements. Similarly, probiotic supplements are not necessarily better at restoring your helpful gut microbes than the probiotics you'd get naturally from food like yogurt and kefir.

“Prebiotic and probiotic foods seem to behave differently than supplements or pill form," said Daniel-MacDougall. "Dietary supplements which often deliver specific nutrients or bacteria types in high doses should not be taken without careful discussion as they may have unintended effects."

Researchers also don't really know how to predict which patients will (and won't) be helped by these supplements. Wargo said that someday, patient-specific prebiotic and probiotic supplements could be made based on an individual’s gut microbiome profile, “but they would have to be rationally designed.”

Benefits Beyond Cancer

Wargo said the study's findings could be applied more broadly: the authors believe that having a healthy gut microbiome could lead to better outcomes for patients with other types of cancer, too.

The bottom line? Don't wait until you get sick to start thinking about how your diet affects your health and wellbeing. The food you eat is, in a way, its own kind of medicine. It may even help prevent some negative health outcomes.

“We can all learn something from this,” said Wargo. “Your diet and what you put into your body matters. I don’t think there’s any substitute. We all need to eat well.”

What This Means For You

New research has shown that some patients with melanoma might have a better response to treatment if they eat a high-fiber diet that supports their gut microbiome.

However, a high-fiber diet is not the best fit for everyone. Before increasing how much fiber you eat, talk to your doctor—especially if you're being treated for cancer.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Spencer CN, McQuade JL, Gopalakrishnan V, et al. Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy responseScience. 2021;374(6575):1632-1640. doi:10.1126/science.aaz7015

  2. Gopalakrishnan V, Spencer CN, Nezi L, et al. Gut microbiome modulates response to anti–PD-1 immunotherapy in melanoma patientsScience. 2018;359(6371):97-103. doi:10.1126/science.aan4236

  3. Asnicar F, Berry SE, Valdes AM, et al. Microbiome connections with host metabolism and habitual diet from 1,098 deeply phenotyped individualsNature Medicine. 2021;27(2):321-332. doi:10.1038/s41591-020-01183-8

  4. Hagan T, Cortese M, Rouphael N, et al. Antibiotics-driven gut microbiome perturbation alters immunity to vaccines in humansCell. 2019;178(6):1313-1328. doi:10.1016/j.cell.2019.08.010

  5. Johns Hopkins Medicine. Fecal transplantation (bacteriotherapy).

  6. National Center for Complementary and Integrative Health. Probiotics: What you need to know.

By Cyra-Lea Drummond, BSN, RN
 Cyra-Lea, BSN, RN, is a writer and nurse specializing in heart health and cardiac care.