Cancer Diet: What to Eat Before, During, and After Treatment

Written by Nichole Owens
Medically Reviewed by Melinda Ratini, MS, DO and Jabeen Begum, MD on February 10, 2023
7 min read

A so-called “cancer diet” is a dietary plan created to help people with cancer during their treatment and recovery. It’s not a one-diet-fits-all approach. Your doctor will tailor your diet to meet your unique needs.

What you eat is important when you have cancer. Your body needs enough calories and nutrients to stay strong. But the disease can make it hard to get what you need, which can be different before, during, and after treatment. And sometimes, you won’t feel like eating.

You don’t need a drastic diet makeover — just a few simple tricks to make healthy foods easy and appealing.

Start focusing on healthy foods even before you begin your treatment. You don’t know how it will affect you or what kind of side effects you might have. So start your good nutrition habits now. It can help you feel better and your body stay strong.

“A healthy, balanced diet that includes a variety of whole grains, fruits, vegetables, beans, nuts, and healthy proteins while limiting processed meats and processed foods is recommended for cancer prevention for all types of cancer,” says Elaine Siu, a lead on the Clinical Nutrition Service team at City of Hope in Newnan, Georgia. 

Siu says this is also a good time to stock your fridge or pantry with ready-to-eat or easy-to-make snacks, such as yogurt, frozen fruit, nuts, soups, or saltine crackers, in case of nausea. Ready-made nutritional shakes are also good to have on hand for days when you’re not feeling well or able to eat.

You may also get help from some friends and family who can bring you meals for the first days or weeks of your therapy.

You may have days when you feel hungry, and others when food is the last thing you want. During this phase, your goal is to get the nutrients your body needs, even if it’s the bare minimum.

Side effects of treatment, such as nausea, taste changes, and fatigue, can make it hard to keep food down. Try to eat small, frequent meals and bland foods, such as:

  • Farina (such as Cream of Wheat)
  • Saltine crackers
  • Fruit
  • Eggs
  • Cottage cheese

Healthy proteins

It’s important to eat enough protein. That will keep your body strong and help repair damage from your cancer or its treatment.

Healthy foods that are high in protein include:

  • Lean meat, chicken, and fish
  • Eggs
  • Beans, nuts, and seeds
  • Cheese, milk, and yogurt

You can also eat plant-based proteins, which have the added benefit of fiber. Good options include:

  • Lentils
  • Legumes
  • Beans
  • Peas

Fruits and vegetables

The National Cancer Institute recommends eating one to two-and-a-half cups of fruits and one to four cups of vegetables daily. These foods contain fiber and help boost your immune system. 

Include dark green and deep yellow veggies and citrus fruits like oranges and grapefruits. Colorful foods like these have many healthy nutrients. 

Always wash fruits and veggies before you eat them.

Hydrating liquids

Cancer treatments can dehydrate you. So can their side effects, such as vomiting, diarrhea, and fever.

Drink plenty of fluids as part of your cancer diet. Other than water, some healthy hydration choices include milk, sports drinks, tea, and coffee.

Moist foods, such as soup, gelatin, yogurt, and pudding, can also help you stay hydrated.

Calorie-dense foods

Cancer and cancer treatment are hard on your body. On the days when you do have an appetite, choose foods that are heavy in calories. This will help you maintain your weight.

Here are some quick ways to add calories to your food:

  • Add butter or oils to foods such as bread, rice, or noodles.
  • Add avocado or guacamole to salads or sandwiches.
  • Spread peanut butter or other nut butters on bread or fruit.
  • Drink calorie-dense beverages, such as fruit juice, milkshakes, and smoothies.

Many side effects of cancer treatments can make it hard to get enough to eat. Your diet may help you get past some of the most common issues.

Nausea/vomiting. Avoid high-fat, greasy, or spicy foods, or those with strong smells. Eat dry foods such as crackers or toast every few hours. Sip clear liquids such as broths, sports drinks, and water.

Mouth or throat problems. For sores, pain, or trouble swallowing, stick to soft foods. Avoid anything rough or scratchy, as well as spicy or acidic foods. Eat lukewarm (not hot or cold) meals. And use a straw for soups or drinks.

Diarrhea and constipation. For diarrhea, it’s important to stay hydrated. Drink lots of liquids, and cut back on high-fiber foods such as whole grains and vegetables. If you’re constipated, slowly add more high-fiber foods to your diet and have plenty of liquids.

Change in taste. Treatment can affect your taste buds. Things you didn’t like before might taste good now. So, be open to new foods. See if you like sour or tart flavors, such as ginger or pomegranate. Spices such as rosemary, mint, and oregano might also help you enjoy other foods.

Always check with your doctor before using supplements, as many of them can affect your treatment. 

But if you’re not eating as much as normal or side effects such as diarrhea and vomiting are causing you to lose important nutrients, a multivitamin might be a good idea. You might also ask your doctor whether you need a vitamin D supplement. Experts say people who are having cancer treatment often don’t get enough.

“It is best to get nutrients from foods, as each food not only provides that single nutrient, but also a variety of other benefits,” Siu says. “For example, a tomato not only provides vitamin C but is also a good source of potassium, vitamin K, beta-carotene, fiber, and the antioxidant lycopene.”

If you’re trying to stimulate your appetite, it’s a good idea to avoid a supplement claiming to do so. “There are no well-tested, over-the-counter appetite stimulant supplements,” says Gabriella Nowicki, MS, RDN, of Annapolis, MD.

Stay away from foods high in hydrogenated oils, which can increase inflammation.

You should also avoid:

  • Highly processed foods
  • Soft-cooked eggs
  • Undercooked or raw fish, such as sushi
  • Unpasteurized dairy products

Your goal after you finish cancer treatment is to rebuild your body and maintain your long-term health. Your nutrition needs will depend on the type of cancer you had and the treatment you received.

In general, a balanced diet heavy in fruits and vegetables, whole grains, and legumes may help reduce the risk of your cancer coming back.

Plenty of people tout “special” diets that they say will help treat cancer or keep it from coming back. Maybe you’ve heard that you should go vegan, vegetarian, or start a raw diet. Before you make any major changes, talk to your doctor.

There’s no magic cancer-fighting diet. There’s also no good research that shows that any eating plan, such as a vegetarian diet, for example, can lower the chance of cancer coming back.

Your best bet is to stick to a balanced diet with lean proteins, fruits, vegetables, whole grains, and low-fat dairy. Limit your intake of sugar, caffeine, and salt, and avoid alcohol.

Ketogenic diet and cancer

In this diet (which is popular for weight loss), you take in a very low amount of carbohydrates. This puts your body into a state called ketosis, where your body burns fat — instead of glucose — for energy.

Even though previous studies have found that the ketogenic diet might help fight cancer, recent studies show that it could cause tumors to spread.

Alkaline diet for cancer

This diet is based on the idea that if we eat certain foods, we can change our body’s pH level and prevent certain health conditions, such as cancer.

Nowicki says the alkaline diet does not help prevent cancer. “Our bodies run a very tight ship when it comes to pH regulation and will do everything they can to keep it stable,” she says.

“If it strays even slightly, it can cause serious health issues like metabolic alkalosis or metabolic acidosis, which can be dangerous.”

Gerson therapy for cancer

An American doctor introduced this diet in the 1940s. It claims to prevent cancer by removing toxins in the body caused by the environment and processed foods.

Gerson therapy is not approved by the FDA.

There is no one magic diet for cancer. Your doctor will suggest a cancer diet based on your unique needs and the type of cancer you have.

In general, a plant-based diet that’s high in protein, fiber, and unsaturated fats is best. You should also limit added sugars, sodium, and saturated fats.

Over the years, there have been many claims that different types of diets can cure cancer. Most of these are false.

Be sure to discuss your cancer diet with your doctor and registered dietitian.

Does Diet Coke cause cancer?

Research suggests that the artificial sweeteners used in Diet Coke and other sodas, including aspartame, are generally safe and do not cause cancer. 

What are the top 5 cancer-fighting foods?

There is no magic cancer-fighting diet, but some plant-based foods that are loaded with natural compounds can reduce your risk for diseases such as cancer. These include: 

  • Vegetables
  • Seeds and nuts 
  • Beans
  • Whole grains
  • Fruits

Which spice kills cancer cells?

In recent years, there has been growing interest in turmeric, a spice used in Asian dishes, as a cancer-fighting spice. Studies are limited, and more research is needed.

What is the best drink for cancer patients?

There is no one best drink if you have cancer. Clear liquids, such as water, can help reduce the side effects of your treatment. So-called full liquids — like fruit juices, vegetable juices, and purees — can help give you the nutrients you need to keep your strength and help you recover.