13 Foods and Supplements to Avoid During Chemotherapy
What to avoid during chemotherapy.
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Nutrition plays an important role in cancer treatment. Healthy fats, protein, vitamins, and minerals maintain energy levels, keep the body strong, and prevent weight loss. But not all foods and nutrients are equally safe to eat during chemotherapy. Cancer cells attack rapidly dividing cells, including the cells of your immune system that normally fight infections. When the immune system is weakened, you are at greater risk for infections and foodborne illnesses.
"Some foods and supplements can also interact with chemotherapy drugs, either by affecting how the body absorbs, metabolizes, or eliminates the medication, or by increasing side effects," says Lily Lichtenstein, RD, a clinical dietitian at Tufts Medical Center in Boston. "Because of these risks, it's important for patients to discuss all dietary changes and supplement use with their oncology care team."
Be sure to talk to your doctor before taking any supplements to make sure they won’t interact with any of your medications, even if you are not undergoing chemotherapy.
To prevent unwanted interactions, worsening of treatment side effects, or foodborne infections, avoid these 13 foods and supplements while on chemotherapy.
Chemotherapy drugs may interact with some foods and supplements, or worsen side effects. It’s important to discuss all dietary changes and supplement use with your cancer care team.Everyday Health
1. Unpasteurized Milk
Dairy milk is a rich source of nutrients like calcium, protein, potassium, and B vitamins. Most milk is pasteurized with heat to kill the germs that cause illnesses. Because raw milk is unpasteurized, it can carry bacteria like salmonella, E. coli, and listeria.
Unpasteurized milk (and juice) is especially dangerous for people with an immune system weakened by cancer treatment. "There's a huge trend with raw milk right now," says Carly Roop, RD, a clinical dietitian specialist at Penn Medicine's Abramson Cancer Center in Philadelphia. "We would not recommend raw milk because you could potentially put yourself at risk for [bacteria] like listeria."
2. Grapefruit
Like other citrus fruits, grapefruit is a good source of vitamin C, potassium, and dietary fiber. It's a healthy, low-fat way to meet your recommended daily fruit allowance. Yet both grapefruit and its juice can interact with many different medicines, including some chemotherapy drugs. That's why grapefruit is one of the foods to avoid while on chemotherapy, says Roop.
3. Raw or Undercooked Meat, Poultry, Fish, and Eggs
Protein needs increase during chemotherapy treatment, in part because this nutrient is important for maintaining muscle mass and strength. Lean meat, poultry, fish, and eggs are good protein sources, but they need to be cooked thoroughly to kill germs like salmonellaand E. coli. Avoid rare meat until your doctor gives you the okay.
Salmonellabacteria also hides in eggs, which need to be cooked all the way through, too. Don't eat them soft-boiled or over-easy. Also avoid any foods that contain raw eggs, such as unbaked cookie dough and cake batter, some Caesar salad dressings, and hollandaise sauce.
Keep raw and incompletely cooked foods separated from cooked foods. You should be keeping your cooking utensils separate for raw and cooked foods as well, to avoid cross-contamination.
4. St. John’s Wort
St. John's wort is an herb that some people take to manage depression, anxiety, sleep disorders, or menopause symptoms. In addition to potential side effects like headache and nausea, this supplement can make chemotherapy medications less effective.
That's because St. John's wort acts on enzymes that help the body break down and remove drugs in the liver. Older research shows that it may cause the liver to remove chemotherapy drugs more quickly than usual, making them less effective. No newer research is available, as St. John’s wort is generally not recommended by healthcare professionals, as it can be unsafe in several circumstances, such as when taking certain medications. If you've been using St. John's wort, stop at least one week before starting cancer treatment. And don't begin taking this supplement during cancer treatment without your doctor's okay.
5. Sprouts
Any raw fruits and vegetables may be problematic during cancer treatment, because they can carry infection-causing germs on their surface, says Lichtenstein. That's especially true for alfalfa and bean sprouts. These foods grow in warm, moist conditions, where it's easy for bacteria like salmonellaand E. coli to attach to them. Do not eat sprouts, as they cannot be thoroughly washed.
Other raw fruits and vegetables are safe as long as they are thoroughly washed under running water. If you have neutropenia, consult your doctor for a specialized diet plan, which might cut out all raw fruits and vegetables entirely.
6. Unpasteurized Cheeses
Pasteurized cheeses like cheddar, Parmesan, and American are safe to eat during cancer treatment (they should say "pasteurized" on the package). Avoid unpasteurized cheeses like these (often soft cheeses), which can carry bacteria:
Brie
Camembert
Roquefort
Bleu
Gorgonzola
Stilton
Cotija
Queso blanco fresca
7. Echinacea
Echinacea supplements help to boost the immune system and treat colds and flu. While this herb is safe for healthy people, it may cause problems when used at the same time as cancer medicines. Echinacea blocks enzymes that break down chemotherapy drugs, which can affect the amount of these medicines in the body. Goldenseal, ginseng, and kava are other supplements to avoid because of potential interactions with cancer treatments, says Lichtenstein.
8. Sushi
Stay away from both sushi and sashimi during chemotherapy treatment. In fact, any raw or undercooked fish and seafood (clams, mussels, oysters) can contain bacteria that cause norovirus, hepatitis A, and other serious illnesses. Cooking fish and seafood thoroughly before you eat them will kill any harmful germs.
9. Hot Sauce
Chemotherapy sometimes causes inflammation and painful sores inside the mouth, called mucositis. Eating spicy foods irritates the sores. "For patients experiencing mucositis as a side effect of their treatment, avoid foods that are spicy, acidic, sharp, or crunchy to prevent further pain and discomfort," Lichtenstein says.
10. Antioxidant Supplements
Antioxidants like vitamins A, C, and E, and carotenoids protect healthy cells from damage caused by oxidative stress. Those same mechanisms could also protect cancer cells and make treatment less effective. "Antioxidant supplements may interfere with the oxidative stress mechanism that some chemotherapy agents rely on to destroy cancer cells," says Lichtenstein.
11. Ice Cream
Extreme sensitivity to cold is a possible side effect of the chemotherapy drug oxaliplatin, which treats colorectal, pancreatic, stomach, and esophageal cancers. Touching foods straight out of the refrigerator and freezer, or eating or drinking cold foods and beverages may be very uncomfortable. "Have gloves by the fridge, let foods get to room temperature, and choose warm beverages," Roop suggests. Depending on the severity of the cold sensitivity, you may want to avoid ice cream, milkshakes, and smoothies while you're on chemotherapy.
12. Garlic Supplement
Garlic has the potential to promote cardiovascular health and regulate the immune system. It has also shown some anti-cancer effects. But because garlic supplements can interact with enzymes that break down chemotherapy drugs in your body, it's best to avoid them during treatment. You can still safely add garlic seasoning to your food for flavor, says Lichtenstein.
13. Deli Meat
Stop eating deli meats like ham, liverwurst, salami, and bologna, which have been linked to listeria outbreaks. Processed meats also are linked to a higher risk of cancer — another reason to limit your intake, even after chemo treatments.
Eating cheese that was sliced at the deli counter isn't recommended either, because it could be cross-contaminated with germs from deli meats. It's safer to buy prepackaged cheese.
The Takeaway
Chemotherapy can weaken the immune system and increase the risk for infections or complications. Eat only pasteurized and well-cooked foods to avoid foodborne illnesses.
Some vitamin and nutrient supplements — such as St John’s wort, garlic, and vitamins A, C, and E — may interact with chemotherapy drugs and make cancer fighting drugs less effective.
Get dietary advice from a healthcare professional, and talk to your oncologist, registered dietitian, or pharmacist if you currently take any supplements or want to take them.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Woldeselassie M. Therapeutic controversies over use of antioxidant supplements during cancer treatment: A scoping review. Frontiers in Nutrition. December 8, 2024.
Adams M. How to Cope With Cold Sensitivity During Chemotherapy. MD Anderson Cancer Center. April 9, 2021.
Ansary J et al. Potential Health Benefit of Garlic Based on Human Intervention Studies: A Brief Overview. Antioxidants. July 15, 2020.
Recall of Deli Meats Linked to Listeria Expanded. Westchester County. July 31, 2024.
VanThomme G. Processed Meat and Cancer: What You Need to Know. MD Anderson Cancer Center. August 1, 2025.
Reyna Franco, RDN, is a New York City–based dietitian-nutritionist, certified specialist in sports dietetics, and certified personal trainer. She is a diplomate of the American College of Lifestyle Medicine and has a master's degree in nutrition and exercise physiology from Columbia University.
In her private practice, she provides medical nutrition therapy for weight management, sports nutrition, diabetes, cardiac disease, renal disease, gastrointestinal disorders, cancer, food allergies, eating disorders, and childhood nutrition. To serve her diverse patients, she demonstrates cultural sensitivity and knowledge of customary food practices. She applies the tenets of lifestyle medicine to reduce the risk of chronic disease and improve health outcomes for her patients.
Franco is also a corporate wellness consultant who conducts wellness counseling and seminars for organizations of every size. She taught sports nutrition to medical students at the Albert Einstein College of Medicine, taught life cycle nutrition and nutrition counseling to undergraduate students at LaGuardia Community College, and precepts nutrition students and interns. She created the sports nutrition rotation for the New York Distance Dietetic Internship program.
She is the chair of the American College of Lifestyle Medicine's Registered Dietitian-Nutritionist Member Interest Group. She is also the treasurer and secretary of the New York State Academy of Nutrition and Dietetics, having previously served in many other leadership roles for the organization, including as past president, awards committee chair, and grant committee chair, among others. She is active in the local Greater New York Dietetic Association and Long Island Academy of Nutrition and Dietetics, too.
Stephanie Watson is a freelance health writer who has contributed to WebMD, AARP.org, BabyCenter, Forbes Health, Fortune Well, Time, Self, Arthritis Today, Greatist, Healthgrades, and HealthCentral. Previously, she was the executive editor of Harvard Women’s Health Watch and Mount Sinai’s Focus on Healthy Aging. She has also written more than 30 young adult books on subjects ranging from celebrity biographies to brain injuries in football.
