13 Foods and Supplements to Avoid During Chemotherapy
These 13 foods and supplements may increase your risk of foodborne illness, interact with your cancer medications, or worsen treatment side effects.
Published on September 4, 2025
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13 Foods and Supplements to Avoid During Chemotherapy
What to avoid during chemotherapy.
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.
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 salmonella and E. coli. Avoid rare meat until your doctor gives you the okay.
Salmonella bacteria 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 salmonella and 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.
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Reyna Franco, RDN
Medical Reviewer
Member of American College of Lifestyle Medicine
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 Col...
Stephanie Watson
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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, ...