Some side effects of metastatic breast cancer (MBC) treatment can make eating uncomfortable or unappealing. Nausea, fatigue, mouth sores, and constipation are common, and when eating is difficult, it’s easy to fall behind on the nourishment your body needs. Sufficient calories and nutrients can help you maintain energy, support your immune system, and avoid treatment interruptions, says Alison Tierney, RD, a board‑certified oncology dietitian and cancer survivor.

Though it’s not always easy, small tweaks, like changing food choices, textures, or meal timing, can be helpful on difficult days. It’s also important to loop in an oncology dietitian for personalized support and let your cancer care team know early if eating becomes challenging. With that in mind, we asked oncology experts to share some foods and strategies that can help you manage the most common MBC treatment side effects.

Many people find nausea to be one of the most frustrating side effects of MBC treatment. When you’re feeling nauseated, food might be the last thing you want to think about. Here’s how to get nourishment even on queasy days.

Choose Bland Foods

On days when nausea is especially bad, opt for bland, easily digestible foods, says Gabrielle Haskell, RD, a clinical dietitian for oncology at the OSF HealthCare Cancer Institute. Saltine crackers, white toast, plain pasta, applesauce, or a banana are good choices.

And try eating something small before you get moving for the day, says Erin Holley, RD, a clinical dietitian at the Ohio State University Comprehensive Cancer Center. A few crackers or a slice of toast before getting out of bed can help.

Eat Small Meals Often

Haskell recommends six to eight small meals throughout the day instead of three larger ones. For example, you can try:

• White toast with peanut butter, sliced banana, and a drizzle of honey

• Shredded chicken with mashed sweet potatoes, and a little olive oil

These combinations provide protein, easy-to-digest healthy fats, and fiber, to give your body energy without overloading your stomach, says Haskell.

If drinking feels easier than chewing, smoothies can help you get in calories and nutrients, says Haskell. Try blending banana, nut butter, oats, or protein powder into a nutritious smoothie.

Ginger tea, ginger chews, or ginger ale may settle your stomach, says Tierney. But skip them if you don’t like the flavor.

Minimize Food Smells

Hot foods release stronger aromas, which can worsen nausea. Letting meals cool before eating or choosing foods straight from the fridge may help, says Holley. Soups and broths can be cooled to room temperature or quickly chilled with an ice cube.

You can also try opening a window, turning on a fan, or eating in a well-ventilated area, says Holley. Use a lid and straw for drinks to limit odors.

What to Avoid

Some foods are simply harder to tolerate when you’re nauseated, so it might be best to avoid them altogether. Our experts note a few common culprits:

• Fried and greasy foods: These take longer to digest and can sit heavily in the stomach, worsening nausea.

• Spicy foods: Hot sauces, chili peppers, and heavily seasoned dishes can irritate the stomach and increase acid production.

• Very sugary foods or drinks: Pastries, candy, or sugary sodas may trigger blood sugar swings that can worsen nausea. Try applesauce or a ripe banana instead to satisfy sweet cravings.

• Foods high in insoluble fiber: Whole-grain breads, nuts, raw broccoli or cauliflower, and seeded fruits like blackberries or raspberries can be irritating when your stomach is unsettled, says Haskell. While they’re healthy and nutritious, these foods may be better tolerated when nausea improves.

Mouth sores can make chewing and swallowing painful, which can interfere with eating. Here are a few strategies you can try to get the nutrition you need when eating is difficult.

Start With Good Mouth Care

Tierney recommends a baking soda and salt rinse to help cleanse the mouth and reduce soreness to help make eating more comfortable.

To make the rinse, mix one cup of water, a ⅛ teaspoon of salt, and a quarter teaspoon of baking soda. Swish it around your mouth gently several times throughout the day.

Choose Soft, Moist Foods

Try softer textures or liquids that allow you to get enough calories without worsening mouth irritation, says Amy Hughes, DO, a board-certified oncologist at Mission Cancer + Blood, a part of University of Iowa Health Care. Soft, smooth foods that don’t require much chewing are often easier to tolerate when your mouth is sore, says Dr. Hughes. Good options include:

• Applesauce

• Yogurt

• Mashed potatoes

• Soft, cooked vegetables

“Adding broth, soups, sauces, or gravies and pureeing or blending foods as needed can make swallowing much easier,” says Tierney. For soft protein, tofu, creamy nut butters, scrambled eggs, and smooth hummus are often better tolerated, she says.

When solid foods are too painful, smoothies and protein shakes allow you to customize ingredients based on what sounds appealing, says Hughes. Add peanut butter, bananas, berries, Greek yogurt, higher-calorie milk, or even a small scoop of ice cream to increase calories.

Holley adds that smoothies can also be made more nutrient-dense by including spinach or other greens, nuts, nut butters, and seeds like chia or flax.

Experiment With Food Temperature

“Some patients prefer warm foods that soothe the throat, while others find cool foods more comfortable for mouth sores,” says Haskell.

If cooler foods feel better, freeze electrolyte beverages into popsicles or try chilled yogurt and smoothies. If warmth helps instead, soups are a good option and can be boosted with protein using bone broth, chicken, or mashed beans, says Haskell. Choose whatever feels best.

What to Avoid

Foods and drinks that sting or burn can worsen pain when you have mouth sores. Hughes recommends avoiding:

• Acidic foods and drinks: Tomato products, citrus juices, vinegar-based dressings, pickled foods

• Citrus fruits: Oranges, lemons, limes, pineapple

• Spicy foods: Hot sauce, chili peppers, curry

• Crunchy or sharp foods: Chips, crackers, raw vegetables, granola

MBC treatment is usually long-term and can lower your white blood cell count (neutropenia), which weakens your immune system. While no single food can prevent infections, eating a whole-food, plant-based diet can support your immune system and reduce inflammation. Here’s what our experts recommend.

Focus on Key Nutrients From Whole Foods

Nutrients that support the immune system include:

• Protein In addition to repairing tissue and maintaining muscle, proteins build antibodies that fight infection. Chicken, fish, eggs, Greek yogurt, beans, lentils, tofu, and nut butters are all good sources of protein.

• Omega‑3 Fats These healthy fats help reduce inflammation, and thus support immune function. Find them in salmon, sardines, mackerel, walnuts, chia seeds, and flaxseeds.

• Vitamins A, C, D, and E A review of studies found that these vitamins play important roles in immune function, antioxidant defense, and inflammation regulation in cancer patients. Get vitamin A from sweet potatoes, carrots, and leafy greens. Citrus fruits, strawberries, bell peppers, and kiwi are good sources of vitamin C. Find vitamin D in fatty fish and fortified dairy, and vitamin E in nuts, seeds, and spinach.

Haskell notes that these nutrients are best obtained from whole foods when possible. High‑dose supplements aren’t usually recommended during cancer treatment unless your care team has identified a deficiency.Whole, minimally processed foods provide vitamins, minerals, antioxidants, and plant compounds that support immune health, Holley says. The American Institute for Cancer Research recommends filling about two-thirds of your plate with plant foods, such as fruits, vegetables, whole grains, beans, nuts, and seeds, with the remaining third coming from lean protein like chicken or fish.

Support Your Gut Health

Much of the immune system lives in the gut, says Tierney. A review of studies found that plant-based diets support beneficial gut bacteria, which help strengthen the immune system and reduce inflammation.

Helpful gut‑supporting foods include:

• Oats

• Beans and lentils

• Berries

• Leafy greens

• Whole grains

Practice Safe Food Handling

Strict “neutropenic diets” that eliminate fresh fruits and vegetables or any foods that might contain bacteria are no longer supported by research, says Tierney. Instead, focus on these safe food-handling practices.

• Wash all produce thoroughly before eating.

• Use separate cutting boards for produce and raw meat.

• Reheat leftovers fully until steaming.

• Avoid expired foods.

• Use clean preparation surfaces.

• Only consume pasteurized dairy and juices.

What to Avoid

Cut back on ultra-processed foods, which are low in nutrients and high in additives that don’t support healing, says Hughes. Diets that emphasize whole foods over processed ones are associated with better cancer outcomes.

Ultra-processed foods include:

• Prepackaged snacks and chips

• Sugary cereals

• Processed meats (lunch meats, hot dogs, bacon, sausage, jerky)

• Candy and desserts

• Sweetened beverages and sodas

• Fast food

A helpful rule of thumb is to shop mostly around the perimeter of the grocery store, where fresh produce, proteins, and dairy are usually located, says Hughes. The exceptions are whole grains (like brown rice, quinoa, barley, and steel-cut oats) and dried or canned beans, which are all typically found in the center aisles.

Some MBC treatments can trigger inflammation in the body, which can lead to stiff, achy joints. An anti-inflammatory eating pattern can help make joint pain and stiffness more manageable, says Tierney. Research showed that women with metastatic breast cancer who ate a whole food, plant-based diet had reduced inflammation and lower tumor markers after eight weeks. Here’s what to focus on.

Fill Your Plate With Colorful Fruits and Vegetables

Deeply colored fruits and vegetables supply antioxidants and compounds that help regulate inflammation, says Tierney. Try adding the following to your plate.

• Berries Blueberries, blackberries, raspberries, and tart cherries are rich in antioxidants and polyphenols that help reduce oxidative stress. Aim for one cup daily, says Haskell.

• Leafy Greens Spinach, collard greens, kale, and Swiss chard contain anti-inflammatory nutrients. Tierney suggests including these regularly to your meals, lightly cooked. If eating them raw, make sure they’re well-washed.

• Cruciferous Vegetables Broccoli, cauliflower, Brussels sprouts, cabbage, and bok choy contain phytochemicals that help slow inflammation and protect joint health, says Haskell.

• Other Colorful Vegetables Carrots, beets, onions, peas, and squashes provide carotenoids with anti-inflammatory activity.

Add Other Anti-Inflammatory Ingredients

Several other ingredients can help manage joint pain through their anti-inflammatory properties, such as:

• Whole-Soy Foods and Mushrooms Tofu, tempeh, and edamame contain antioxidant compounds. Asian mushrooms like shiitake and maitake can support immune function. But always cook mushrooms thoroughly.

• Healthy Fats Extra-virgin olive oil, avocados, and nuts provide anti-inflammatory fats that may help reduce joint pain. Use these in place of fried or heavily processed fats, says Hughes. Omega‑3s, which we discussed earlier, also help support joint comfort by reducing inflammation. Try adding a tablespoon of ground flaxseed to your oatmeal or a handful of walnuts as a snack.

• Spices Turmeric and ginger contain compounds that can help reduce inflammation. Hughes also suggests curry powder, garlic, basil, and cinnamon. Add these to meals as you can tolerate.

Most people undergoing MBC treatment struggle with fatigue, and the three biggest nutritional factors that can help improve energy are calories, protein, and fluids, says Holley. Here are ways to use food and fluids to support your energy.

Pair Foods Strategically

Eating protein and carbohydrates together can help stabilize blood sugar and support muscle maintenance, says Tierney. Try combinations like:

• Oatmeal with nut butter

• A smoothie with soy milk, banana, and protein powder

• Beans and rice

• Whole‑grain toast with avocado and an egg

Low iron or folate can contribute to low energy. Foods that help include lentils, beans, leafy greens, and fortified cereals. Pairing these with a vitamin C–rich food, if tolerated, can help improve absorption. For example, try lentil soup with a side of bell peppers, spinach salad with strawberries, or black beans with tomatoes.Inflammation can also contribute to fatigue. The same anti-inflammatory foods previously mentioned (whole grains, colorful vegetables and fruits, and omega-3-rich foods) can help manage cancer-related fatigue.

Stay Hydrated

Dehydration, even when mild, can worsen fatigue, says Tierney. Sip fluids consistently throughout the day, rather than trying to drink large amounts at once.

On days when you have diarrhea, reach for electrolytes like sports drinks, coconut water, or oral rehydration solutions to help replace both fluids and minerals.

Choose Low-Prep Meal Options

When you’re too tired to prepare a meal, Tierney suggests leaning on foods that require little to no effort, such as:

• Premade smoothies or protein shakes

• Yogurt cups

• String cheese or cheese cubes

• Precut fruits and vegetables

• Applesauce

Let others help with meal prep and delivery. On days when you have more energy, consider making extra portions to freeze for later.

Treatment medications and anti-nausea drugs can cause constipation. When you combine that with moving, eating, or drinking less because you don’t feel well, your digestive system can slow to a crawl, says Haskell. Food-based strategies can help manage constipation.

Start With Fluids

Before increasing fiber, make sure you’re getting enough fluids, says Tierney. Fluids soften stool and allow fiber to work properly. Aim for about 8 glasses of fluids per day. Without enough hydration, extra fiber can worsen constipation.

Try sipping fluids throughout the day, and include a warm beverage, like a cup of warm prune juice or apple juice, in the morning, which can help get your bowels moving. Haskell says both contain sorbitol, a natural sugar alcohol that can soften stools and stimulate a bowel movement.

Add Fiber Slowly

Once you’re drinking enough fluids, you can start increasing fiber in your diet, but go slowly, says Hughes. This might mean adding one high-fiber food at a time, like switching to whole-wheat bread, then adding a spoonful of chia seeds a few days later. Increasing fiber too quickly in your diet can cause gas, bloating, or stomach discomfort.

Fiber-rich foods that may help include:

• Fruits Prunes, kiwi, pears, figs, berries

• Vegetables Leafy greens, sweet potatoes, carrots, broccoli

• Whole Grains Oats, brown rice, whole-wheat bread

• Legumes Beans, lentils, chickpeas

• Nuts and Seeds Ground flaxseed or chia seeds

If you tend to alternate between constipation and diarrhea, soluble fiber from oatmeal, applesauce, and bananas may help, Tierney says. This type of fiber absorbs water and helps soften stools without irritating the gut.

• Managing metastatic breast cancer treatment side effects through nutrition can help you maintain your strength, tolerate treatment better, and improve your quality of life.

• Choose bland foods for nausea, soft or cool foods for mouth sores, pair protein with carbs for energy, add fiber gradually for constipation, and eat anti-inflammatory foods for joint pain.

• Staying hydrated, practicing safe food handling, and limiting ultra-processed foods can help support your immune system and overall health throughout treatment.

• If eating becomes very difficult or side effects are interfering with your ability to get enough nutrition, reach out to your oncology team early.