Immunotherapy represents a transformative approach in cancer care, utilizing the body’s own immune system to identify and destroy cancer cells, often through agents like checkpoint inhibitors or cellular therapies. Nutrition serves as a supportive framework for the body during this process, helping to manage side effects and maintain the energy required for the immune response. Before making any significant changes to your diet, consult with your oncology team and a registered dietitian specializing in cancer care for personalized guidance.
Preventing Foodborne Illness and Infection
Immunotherapy can sometimes weaken the immune system, increasing the risk of infection. Certain foods carry a higher microbial load and must be avoided or carefully handled to prevent serious foodborne illness, which can be particularly harmful to an immunocompromised patient.
Patients should avoid raw or undercooked meat, poultry, and seafood, including sushi and ceviche, as these are common sources of bacteria like Salmonella and E. coli. All meats and eggs must be thoroughly cooked until they are well-done and steaming hot. Deli meats, such as sliced turkey or ham, and cured meats like salami, should also be avoided unless they are heated until steaming hot.
Unpasteurized dairy products, including raw milk and cheeses made from unpasteurized milk, pose a significant risk due to the potential presence of Listeria. This includes soft cheeses like Brie, Feta, and Camembert. Even some pasteurized soft cheeses that are mold-ripened or blue-veined should be avoided unless cooked. Raw fruits and vegetables must be meticulously washed and peeled, or avoided entirely if they cannot be thoroughly cleaned, such as raspberries or broccoli florets.
Strict attention must be paid to food preparation to prevent cross-contamination. This includes using separate cutting boards for raw meat and produce, and never placing cooked food on a plate that previously held raw ingredients. Untreated well water or unpasteurized juices and cider should be avoided unless they have been boiled or are specifically labeled as filtered or distilled.
Dietary Components That Exacerbate Gastrointestinal Side Effects
Immunotherapy frequently leads to inflammation of the digestive tract, known as immune-related colitis, which presents as diarrhea, nausea, or abdominal pain. When experiencing acute gastrointestinal distress, certain dietary components can worsen these symptoms by irritating the gut lining or being difficult to digest. Dietary modification during these flare-ups aims to soothe the gut and reduce inflammation.
Foods high in fat, such as fried foods, greasy meats, or rich desserts, should be limited because fat is more difficult to digest and can increase gut motility. High-fiber foods can also be irritating to an inflamed colon. During periods of active diarrhea, a low-fiber or bland diet focusing on refined grains like white rice and white bread is often recommended. High-fiber foods to limit include:
- Raw vegetables
- Whole grains
- Nuts
- Seeds
Acidic foods, including citrus fruits, tomato products, and vinegar-based dressings, can irritate the mucous membranes of the mouth and throat. Spicy foods, such as those containing chili, hot sauce, or curry, should also be avoided. Beverages containing excessive caffeine or simple sugars can stimulate the gut, leading to increased fluid loss and diarrhea.
Supplements and Herbal Remedies That Interfere with Immunotherapy
The use of concentrated supplements and herbal remedies during immunotherapy requires caution due to the risk of chemical interactions with the treatment drugs. Many herbal products contain biologically active compounds that can either reduce the effectiveness of the drug or increase its toxicity. These interactions often occur because the compounds interfere with the liver enzymes responsible for drug metabolism.
Grapefruit and grapefruit juice are well-known examples of this interaction, as they contain furanocoumarins that inhibit cytochrome P450 enzymes in the liver, which can lead to high concentrations of certain medications in the bloodstream. St. John’s Wort, an herbal supplement sometimes used for mood support, has the opposite effect, inducing these same liver enzymes, which can cause the immunotherapy drug to be metabolized too quickly.
Supplements marketed to “boost” the immune system, such as high-dose Echinacea or certain medicinal mushrooms, are generally discouraged because their immunomodulatory effects are unpredictable in the context of immunotherapy. These compounds could interfere with the delicate balance of immune activation that the cancer treatment is designed to achieve. Furthermore, high-dose antioxidant supplements, including large amounts of Vitamin C, Vitamin E, or beta-carotene, are sometimes cautioned against because they might protect cancer cells from the oxidative damage intended by some anti-cancer treatments.
Probiotics and fermented foods, which contain live and active bacterial cultures, should be discussed with the care team, as there are varying clinical opinions and a potential, though small, risk of infection in immunocompromised patients. The general rule remains that any concentrated compound that can alter the immune system or drug metabolism should be cleared with the oncologist before consumption to ensure treatment safety and efficacy.