The food choices we make should be decided upon with great consideration, some people more than others. For instance, a person’s diet can affect how well immunotherapies work against cancer. High-fiber diets are good because they can change gut microbes and make these therapies more effective. Taking probiotics is not good because they could do the opposite.
A growing number of studies tell us that consuming more probiotics — live microorganisms often touted for their health benefits — can lead to reduced diversity in the gut microbiome. This is particularly detrimental to cancer patients on immunotherapy. High-fiber diets, on the other hand, may help a type of immune therapy work better against tumors. So, eating more foods high in fiber has been recommended to prevent cancer.
Take this recent study (which was presented at a news conference held by the American Association for Cancer Research) for example. They found that cancer patients being treated with immune therapy did worse when their diets were supplemented with probiotics. They also found that patients who had diets rich in high-fiber foods, such as whole grains, fruits, and vegetables, showed marked improvements in the effectiveness of their treatment, as well as higher gut flora diversity.
The Study
- Spencer and colleagues at MD Anderson Cancer Center in Houston examined 113 people with melanoma.
- The participants were getting a kind of immune therapy called PD-1 blockade or checkpoint inhibition.
- Each patient was surveyed about their diet, including the use of probiotics, and fecal samples were collected.
The Results
- Those who ate a high-fiber diet were five times as likely to have the therapy halt the growth of or shrink tumors as those on diets low in fiber.
- Meanwhile, 40 percent of patients in the study who said they were taking probiotics saw a decrease in their gut microbe diversity.
- High-fiber diets seem to foster a more diverse collection of gut microbes, which is associated with better outcomes from PD-1 blockade therapy.
- But probiotic supplements — pills or food supplements that are supposed to contain helpful bacteria — actually reduced the diversity of microbes in cancer patients’ guts.
Microbiome Diversity Is Essential
Our microbiome plays a major role in activating our body’s immune response, which is why gut flora diversity is particularly important for patients on immunotherapy. Normally, around 20 to 30 percent of cancer patients see their tumors stop growing or shrink with PD-1 blockade immunotherapy. The reason for this is still unclear. Spencer and colleagues did find that bacteria in the Ruminococcaceae family seem to improve responses to the treatment, but they don’t know why.
All they know is that some people have more of those helpful bacteria than others for some reason. It is safe to assume that it has something to do with what people are eating since diet is one way to change a person’s microbiome (the collection of bacteria, fungi, and other microbes that live on and in the body). In other words, the best way to improve our chances of having these helpful bugs in our system is to increase microbiome diversity on the whole through what we consume. The research proves this.
The 46 patients who consumed the highest amount of fiber in their diets, including fruits, vegetables, and whole grains, tended to have more of the bacteria associated with a response to the immune therapy. Those were the patients that had a positive effect from the therapy. Participants who ate more processed meat and excess sugar had fewer of those bacteria. Their treatments didn’t go as well, and their tumors were more likely to grow despite immune treatment.
Furthermore, more than 40 percent of patients said they were taking probiotics. Those people had lower gut microbe diversity than people who didn’t take the supplements. Spencer said that “a lot of people have perceptions that probiotics will have health benefits, but that might not be the case for cancer patients.” The new work adds to a growing number of recent studies that have hinted that probiotics may not offer the health benefits doctors and patients have hoped for.
Many studies have linked high-fiber diets to decreased cancer risk and other health improvements, so even if eating more fruit and vegetables doesn’t boost immune therapy’s effectiveness, Sears said, “the upside is you’re probably not hurting anyone with a high-fiber diet.” The researchers’ final note states that even in cases where eating more fruit and vegetables didn’t boost the immune therapy’s effectiveness, no one got worse. Meaning, you can’t go wrong with fiber like you can with probiotics.
