Diet, Health

Study Looks At Link Between Having A Higher Fiber Intake And Lower Melanoma Progression

A new observational study has found a link between eating a high dietary fiber diet with better responses to immune therapy for cancer patients diagnosed with melanoma, which is a type of skin cancer.

The study showed that for every 5-gram (g) increase in daily consumption of fiber had a 30% lowered risk of cancer progression or even death. While this benefit was observed in those that didn’t consume probiotic supplements, but for those that had ‘more of two particular types of bacteria in their gut.’

According to Harvard T.H. Chan, ‘Fiber is a type of carbohydrate that the body can’t digest.’ In addition, ‘Fiber helps regulate the body’s use of sugars, helping to keep hunger and blood sugar in check.’ Fiber can be found in certain foods like fruits and vegetables, as well as in whole grains, all of which have an impressive range of health benefits.

People that have a diet rich in dietary fiber are also known to have better weight control, as well as a lowered risk of developing chronic conditions such as diabetes and heart disease.

Oxford Academic shares that people that eat more fiber tend to have better gut health, which is partially due to the benefits of fiber on the “gut microbiota,” which is the community of microorganisms that live in a person’s intestines.

Over the last decade, scientists have found multiple associations between human health and gut microbiota, especially in the interactions between the immune system and bacteria. Notably, there has been a rise in the use of commercially bought probiotics all due to the idea that they add “friendly” or beneficial bacteria to the gut microbiota in order to improve on one’s health.

A number of studies have shown that a person’s gut microbes can affect their response to immune therapy for cancer, yet there is still a lack of research that focuses on the contribution of diet and probiotic supplements, experts say.

According to professor of genomic medicine and surgical oncology at the MD Anderson Cancer Center in Houston, Jennifer Wargo, M.D. “Research from our team and others has shown that gut microbes impact response to immunotherapy treatment, but the role of diet and probiotic supplements has not been well studied.”


Survival Chances and the Benefits of Fiber

Prof. Wargo and her colleagues led the observational study that looked at patients with melanoma that at high-fiber diets, and how they positively responded better to their immune therapy. What they found was that these individuals were ‘significantly more likely to survive without their cancer worsening after around 13 months of treatment.’

After accounting for the other clinical factors, the researchers also found that with every 5-g increase in daily fiber intake showed an association with 30% lower risk of cancer progression or death. Strangely, the study authors also noticed that people that ate satisfactory amounts of fiber, but did not take any commercially available probiotic supplements, showed even greater benefits from the treatment.

In addition, the research group also saw that the ones who responded well to immune therapy also had a higher amount of a family of bacteria known as Ruminococcaceae, as well as another species called Faecalibacterium prausnitzii within their gut. These types of bacteria also work to digest fiber and starch.

There were significant difference between those that responded to treatment, and those that did not, more so after the research group accounted for other factors that affected the microbiota, like age, body mass index (BMI) and antibiotic use.

You can find their study published in the Science journal.


Finding the Link Between Probiotic Use and Dietary Fiber

The research team requested for 128 people diagnosed with melanoma to answer a questionnaire to assess their diet and their use of probiotic supplements within the past month. The team also analyzed fecal samples to see the relative diversity and abundance of bacterial species living with the participants’ guts.

The participants were also beginning to take anti-cancer drugs called immune checkpoint inhibitors. These work by preventing the immune cells from switching off before they kill the cancer cells. To have the proper gauge in the study, the scientists also defined “sufficient” daily intake of dietary fiber to be ‘at least 20 g of fiber from fruit, vegetables, legumes, and whole grains.’

What they found was that from the 128 participants, only 37 of them met the criterion of “sufficient” fiber intake. After looking at an average of 13 months of treatment, these participants were also found to have a significantly likelier chance of survival without their cancer also progressing.

Of the 22 people that reported a sufficient amount of fiber intake and no probiotic use, at least 18 (or 82%) of them responded to immune therapy. On the other hand, out of 101 people that reported an insufficient fiber intake or who took probiotics, at least 60 (or 59%) responded to the treatment.

Researchers also share that probably due to the small participant number of the study, there was no ‘statistically significant link between probiotic use alone and response to treatment.’


What’s the Cause and Effect?

Because this was an observational study, the research that was done couldn’t prove that dietary fiber was directly responsible for actual improvements in people’s treatment response, or if probiotics managed to reduce the benefits.

Additionally, the research group also noted that they had to rely on the participants’ abilities to recall the kinds of food they ate, as well as their use of probiotics supplements, which may or may not be accurate.

Co-first author Jennifer McQuade, M.D., led another ongoing randomized clinical trial, this one with an aim is to provide stronger evidence of how diets with varying fiber content and the way it affects the microbiome and response to immune therapy in individuals with melanoma.

For the newly published study, the scientists also conducted tests in animal models of melanoma in order to help confirm the results of their observational findings. They noted that when they fed mice a low-fiber diet or probiotics, the animals were observed to not respond as well to immune therapy as compared to the mice control group.

Moreover, the research group also found that the mice that ate a low-fiber diet or probiotics also had less immune cells, which are called cytotoxic T cells, in their tumors.

In conclusion, the authors share, “Together, these studies support the need for more careful investigations of the effects of current commercially available probiotic formulations on immunity and cancer immunotherapy response.”


Probiotics Could Have a Disruptive Effect

In an interview with Medical News Today (MNT), Prof. Wargo said, “[I]f you have a sufficient dietary fiber intake, by taking commercially available probiotics, you may, in fact, harm your response to cancer immunotherapy.”

While not necessarily confirmed, she also speculated that the bacteria in probiotics may disrupt the gut microbiota in one way or another.

She shared, “If you think about these commercially available probiotics, it tends to be one particular species and to a high extent. It could throw off the balance of the gut.”

In fact, Prof. Wargo shared that the experiments actually found that probiotics in mice had reduced diversity of their gut microbiome, which is worse for their health, causing an impaired response to immune therapy.

Although other studies claim that probiotics are beneficial, Prof. Wargo also explained, “people need to really be aware that they may not help and they may in fact harm.”

As for senior vice president of scientific and regulatory affairs at the Council for Responsible Nutrition, Dr. Andrea Wong, she told MNT that probiotics do have a wide range of health benefits.

She shared, “While probiotics are most widely known for their role in maintaining digestive health, research shows benefits of specific organisms for immune function, brain health, oral health, and heart health, among others, and the body of scientific research supporting the use of probiotics continues to grow.”

But she also emphasized that since cancer is quite a complex disease, interventions that are known to complement their treatments should really be “carefully and extensively studied” if they could truly benefit patients.