Practical Tips: Foods to Support Your Microbiome during Cancer Treatment

Our bodies host trillions of microorganisms, primarily in our gut. In fact, they outnumber our own body’s cells! These guests make up what is called our “microbiome.” When these microorganisms are in a healthy balance, they support many of our body’s functions such as intestinal wall integrity, metabolism, optimal immunity, inflammation control, brain and nervous system health, and mood function. 

Chemotherapy can disrupt the gut microbiome, which can affect treatment outcomes.1 Radiation to the abdominal or pelvic area can damage the lining of the gut and alter the microbiome.2 A growing body of evidence suggests that the microbiome influences the effectiveness of immunotherapy treatments. Certain microbes are associated with improved responses, though the research is complex, making it difficult to make general recommendations.3  

One of the main ways we can support our microbiome is through our diet.

Strategies to support your microbiome during treatment

1. High-fiber diet 
   Consuming whole grains, leafy greens, fruits, vegetables, legumes, and nuts support a diverse microbiome, and feed beneficial gut bacteria.

   • Microorganisms in your gut ferment the fiber you feed them and make a helpful substance called butyrate, which becomes their key energy source. Butyrate also improves the health of the GI tract by decreasing inflammation, protecting the barrier lining of the intestines, promoting a healthy microbiome and protecting against cancers such as colon cancer, and more.4 

   • Specific foods to help with butyrate production include:

     • Whole grains: oatmeal, brown rice, quinoa, whole wheat

     • Legumes: beans, lentils, chickpeas

     • Fruits: high-pectin fruits such as apples, berries

     • Vegetables: garlic, onions, carrots, leafy greens, cruciferous vegetables such as broccoli, cooked and cooled potatoes (high in resistant starch)

     • Nuts and seeds: flax and chia seeds, almonds, walnuts, peanuts

     • Full-fat dairy products in moderation: yogurt, butter, cheese, ghee, milk 

2. Fermented foods 
   Deliver probiotics safely to the gut, creating a healthy and diverse microbiome. Fermentation also enhances digestibility and generates additional nutrients such as vitamins and antioxidants. Other health benefits include a reduced risk of cardiovascular disease, diabetes, and obesity.5

   • Examples of fermented foods:

     • Yogurt 

     • Tempeh

     • Miso

     • Pickled vegetables, kimchi, sauerkraut (naturally fermented) 

     • Kefir 

     • Kombucha 

     • Sour cream 

     • Apple cider vinegar

   • If you have a weakened immune system, avoid:

     • Cheeses and yogurts made with raw/unpasteurized dairy products

     • Unpasteurized drinks such as unpasteurized kombucha or raw milk 

     • Check with your oncologist or oncology dietician to see if unpasteurized foods or beverages are safe for you.

3. Prebiotics
   Stimulate the growth of beneficial bacteria and promote the production of short-chain fatty acids (SCFAs) like butyrate, which have evidence for supporting beneficial bacteria. It has become common for the food industry to add prebiotic supplements like Inulin to prepared beverages or snacks. However, the best (and tastiest) source of prebiotics comes from real food:

   • Garlic

   • Onions

   • Bananas

   • Whole oats

   • Apples

   • Dandelion greens

4. Probiotics 
   Probiotic supplements introduce beneficial bacteria to the gut, but choosing the right probiotic can be complex. The strain of the microbe matters. Whether and which probiotic to use is best guided by your physician, as conditions like low immunity may increase the risk for complications. Find an integrative practitioner to explore a personal probiotic regimen. 

Originally published on CancerChoices.org 2025