The Benefits and Risks of Probiotics During Chemotherapy

If you have cancer, chemotherapy might be prescribed. But while this regimen is designed to attack cancerous cells, healthy cells can be affected as well, including those in the digestive tract. A possible fix? Probiotics, or the "friendly bacteria" found in yogurt, fermented foods and supplements.

In fact, this "good" bacteria may relieve some of the digestive side effects of chemo treatments. "Chemotherapy can cause diarrhea. Probiotics may ease the severity and frequency of this condition, and they may reduce the need for anti-diarrheal medications," says Adil Akhtar, MD, an oncologist, palliative care expert and associate professor at the Oakland University-William Beaumont School of Medicine in Auburn Hills, Michigan.

But probiotics may not be the best course of action for everyone. "Recent studies have shown that probiotics may be associated with a poor response to the new class of drugs called immunotherapy, which stimulates the body's own immune system to fight cancers," says Dr. Akhtar.

Here's what you should know about probiotic use during chemotherapy, including the benefits and drawbacks, as well as good sources of these microorganisms in case they're recommended to you.

Probiotics are live organisms (sometimes referred to as "good bacteria") that are essential to gut health. According the Mayo Clinic, these beneficial germs help to balance out the "bad" bacteria in your gastrointestinal system in order to protect the body's immunity and digestive health.

Two commons types of good bacteria are Lactobacillus bulgaricus and Lactobacillus acidophilus, both of which are found in yogurt, though yeast, such as Saccharomyces boulardii, is also a probiotic. Probiotic supplements also contain beneficial bacteria, though foods with probiotics are often better options unless a certain strain can't be obtained from a food source, according to the Cleveland Clinic.

Read more: Which Type of Yogurt Is Best? The Pros & Cons of 13 Different Kinds

Chemotherapy often damages the cells that line the intestinal tract, which causes inflammation, pain and diarrhea, since the intestines aren't able to absorb nutrients efficiently. According to Memorial Sloan Kettering Cancer Center, probiotic supplementation has been shown to help a variety of digestive tract issues, such as inflammatory bowel disease, gastroenteritis and irritable bowel syndrome, and it can also be part of a treatment plan for chemotherapy-related diarrhea.

However, a large review of studies on the use of probiotics in people with cancer treatment-related diarrhea failed to document a clear benefit. The August 2018 analysis, published by the Cochrane Database of Systematic Reviews, involved 12 randomized controlled trials with 1,554 participants. Most of the studies were low or very low quality, researchers noted. They concluded that the evidence on probiotic use to prevent diarrhea caused by chemo remains inconclusive, and they found no evidence of any treatment benefit.

Consuming probiotics during chemo isn't without risk. Chemotherapy weakens the immune system in part because it damages the bone marrow where immune cells are made, per BreastCancer.org. "People with cancer who are severely immunocompromised or have a central venous catheter should not take probiotics. Severe infection or sepsis due to the presence of bacteria or fungus in the blood have been associated with probiotics," warns Dr. Akhtar.

According to the Dana-Farber Cancer Institute, two other groups of people that should steer clear of probiotics are those participating in a clinical trial with dietary restrictions and people with low levels of neutrophils, which are a type of white blood cell. This condition, which is called neutropenia, can result in an infection of the bloodstream.

Read more: 13 Surprising and Beneficial Probiotic Foods

There are lots of ways to incorporate probiotics into your diet if your physician recommends them to you.

"A few good sources of probiotics include yogurt, unpasteurized sauerkraut, kimchi, buttermilk, sourdough bread, miso, tempeh, kefir and pickled vegetables," notes Dr. Akhtar. Just be sure to read labels carefully, as not every yogurt brand or loaf of bread contains the same good bacteria (for example, look for Lactobacillus acidophilus on yogurt labels).

If you'd rather take a supplement, be sure to ask your doctor for advice. There are numerous types of bacteria and many species within each — and of course, the levels of probiotic bacteria in supplements can vary according brand, per the Mayo Clinic. Because of this variability, it's a good idea to seek help when determining which supplement best matches your needs.

The use of probiotics for treating chemotherapy-related diarrhea may not be recommended in every case, and more research needs to be done to determine which strains are the most effective.

"My advice is to avoid probiotics if you are taking immunotherapy drugs until further studies are done," says Dr. Aktar. And always speak with your doctor about your own individual case before making any changes to your diet or supplements regimen.