Common Nutrition-Related Side Effects

Surgery, chemotherapy and radiation therapy can have a dramatic effect on your ability to maintain proper nutrition. Side effects such as loss of appetite, fatigue, depression, constipation, nausea and mouth sores can limit the types of foods you’re able to eat.

In addition you may experience:

  • Difficulty digesting some foods
  • Changes in taste that make food unappealing
  • Chewing and swallowing problems

Note: We recommend that you see your dentist for a checkup before starting chemotherapy or radiation. Get a head start on your oral health and address any dental issues. If you have not seen a dentist but you have started treatment, talk to your medical team about the best time for a dental visit.

If you lose weight before or during your cancer treatment, tell your medical team.

Unintentional weight loss reflects the loss of muscle mass along with body fat. As a result, you may have:

  • Fatigue, lack of energy
  • Increased risk of infection
  • Delayed wound healing
  • Difficulty coping with the side effects of cancer treatment
  • Unplanned breaks or delays in your planned cancer treatment

To maintain your weight and keep your treatment plan on track, you must:

  • Manage your treatment-related side effects.
  • Get any assistance needed with nutrition interventions.

During treatment, it’s common to lose your appetite. Possible causes include:

  • Side effects of cancer treatment and/or the cancer itself
  • Physical difficulty with eating
  • Changes in the way your body digests food and nutrients
  • Pain
  • Anxiety and/or depression

If you are not feeling particularly hungry, try these tips.

  • Eat smaller meals more often.
  • Snack between meals and before going to bed.
  • Do some light exercise 10-15 minutes before eating to help stimulate your appetite.
  • Adjust the seasonings and flavorings in your food to please your tastes.
  • Try high-calorie, high-protein foods and beverages to get more benefit from a smaller amount of food. Try peanut butter, cheese, cereal with whole milk, yogurt, or liquid nutrition drinks.
  • Set an alert every few hours on your clock or phone to remind you to try to eat something – even if you do not feel hungry.
  • Talk to your medical team about medications that may help stimulate your appetite.
  • Chew your food slowly and thoroughly.
  • Eat small, frequent meals 5-6 times a day instead of three big meals.
  • Avoid carbonated beverages, chewing gum, and foods or beverages that give you gas.
  • Avoid high-fat, greasy foods, and foods high in fiber. These foods can make you feel full for longer periods of time.


  • Experiment with different textures of food. Make them softer and easier to chew and swallow. Try mashed potatoes, cottage cheese, scrambled eggs, oatmeal, yogurt, custards, puddings, gelatin, bananas, or applesauce.
  • Cook foods to a very soft and tender texture.
  • Moisten foods by cooking with broth, gravies, sauces or cream soups.
  • Stews, soups and casseroles are moist meal options.
  • Cut foods into very small pieces, or grind/puree them.
  • Try cold foods that are not too thick such as sherbet or popsicles to soothe mouth soreness.
  • Avoid foods that may be irritating such as:
    • coarse, dry, rough, or fibrous foods (like raw fruits/veggies)
    • coarse whole grain or bran products
    • acidic foods and beverages (such as orange juice, citrus fruits, or tomato sauce).

Mouth Care

  • Oral care is very important. It removes food, promotes healing and avoids infection. Use a soft toothbrush.
  • Rinse your mouth several times a day with water or a homemade mixture of 1 cup warm water, ¼ teaspoon salt, and ¼ teaspoon baking soda.
  • If you prefer a commercial mouthwash, make sure it is alcohol-free.
  • Remove dentures (except during eating) if your gums are sore.
  • Ask your medical team about numbing agents to relieve your mouth/throat pain long enough to eat and drink without pain.
  • If you see small, white patches in your mouth, or if swallowing is difficult or painful, tell your medical team. This could be a sign of infection.

Possible causes: radiation, chemotherapy, or medications. A reduced flow of saliva can change the way foods taste, make it difficult to eat, and, over time, harm your teeth.


  • Sip water or other cool beverages throughout the day.
  • Aim for at least 8-12 cups (2-3 quarts) of liquid a day.
  • If water does not taste good to you, try infusing your water with a wedge of fresh fruit. Or try fruit nectars, 100% fruit juice diluted with water, or electrolyte replacement beverages.
  • If your mouth is not sore, tart foods and beverages may help your mouth make saliva.
  • Suck on popsicles or ice chips.
  • Cook with liquids, or moisten foods with broths, gravies, sauces, or milk to make them easier to chew/swallow.
  • Ask your medical team about products to help coat and protect your mouth, such as saliva substitutes or mouth moisturizers.
  • Try lip balms to prevent dry lips. Use a product that has no flavor or fragrance. Avoid products that contain essential oils, peppermint, citrus, or cinnamon.
  • Rinse your mouth with an alcohol-free mouthwash or a homemade salt and baking soda mixture.
  • Use a cool-mist humidifier in your room while sleeping.
  • Do not smoke or use tobacco products.

Make Your Own Mouth Rinse

  • 1 cup warm water
  • ¼ teaspoon salt
  • ¼ teaspoon baking soda

Mix well. Swish in mouth for 15 seconds and spit out.

Possible causes: chemotherapy, medications, dry mouth.

Tips to prevent or reduce symptoms of taste changes

  • Keep your mouth clean and moist using a mouth rinse.

Rinse your mouth well before eating by swishing a small amount of mouth rinse in your mouth and spitting it out.

Recipe for Homemade Mouth Rinse

Mix together:
1 cup warm water
¼ teaspoon salt
¼ teaspoon baking soda

Use plastic utensils if you have a metallic taste in your mouth.
  • Add some slices of citrus fruit (such as lemon or lime), or an ounce or two of fruit juice to make water taste better.
  • Try some tart foods or beverages as these may taste better during treatment.
  • Try cold or room temperature foods – they may be more appealing than warm foods when your taste perception is a bit off.
  • If things taste too sweet, try adding something sour or bitter to improve its taste.  (For example, try adding some Decaffeinated instant coffee granules to creamy oral liquid nutrition supplements.  Or add a small amount of lemon juice to a fruit smoothie.)
  • Try adding different dried spices or fresh, washed herbs to change the flavor of your foods or beverages.  Condiments, marinades or salad dressings can also help make the flavor of foods more appealing.

Possible causes: surgery or radiation to the head and neck.

If you have trouble swallowing, tell your medical team. You may be sent to a speech language pathologist who can evaluate your swallow. They can also recommend a diet consistency and/or swallowing techniques to keep you comfortable and safe.

Tips to help with swallowing problems

  • Drink liquids at room temperature rather than very hot or very cold temperatures.
  • Thicken liquids to the consistency recommended by your speech pathologist.
  • Eat small, frequent meals.
  • Puree moist foods with a blender or food processor to make them easier swallow.
  • If you require a pureed or liquid diet, ask for a consultation with a Registered Dietitian Nutritionist. They can offer suggestions to help meet your calorie, protein, and fiber needs.
  • Tell your medical team if you have any episodes of choking or coughing while eating, especially if you develop a fever.

Possible causes: surgery, chemotherapy, radiation, and some medications.

Nausea can prevent you from eating enough and can lead to unintended weight loss as well as loss of muscle mass. Address nausea right away. (If you have nausea, you are not likely to eat foods with the most nutritious value.)

Tips to prevent or lessen nausea

  • Take anti-nausea medications as prescribed by your medical team.
  • Eat small meals more often (5-6 times per day).
  • Eat slowly, sitting upright. Remain upright for at least 1 hour after eating. If you need to recline, keep your head elevated.
  • If beverage odors bother you, use a cup with a lid.
  • Foods and beverages with ginger may help reduce nausea.
  • Before and after you eat, rinse your mouth with water or a homemade salt/baking soda rinse.
    • Homemade Mouth Rinse
      • 1 cup warm water
      • ¼ teaspoon salt
      • ¼ teaspoon baking soda
    • Mix well; swish in mouth for 15 seconds” then spit out
  • Chose cold or room temperature foods if you are sensitive to food odors: hot foods produce more odors.
  • Avoid spicy, fried, high-fat, or high-fiber foods and rich desserts.

Specific problems

  • Nausea in the morning: Keep crackers at your bedside to eat before you get up.
  • Nausea during chemotherapy or radiation treatments: Avoid eating 1-2 hours before your treatment. Try bland, soft foods on treatment days.
  • Bad taste in your mouth: Suck on peppermint or lemon candy.
  • Sensitive to food smells: Eat in a well ventilated room to avoid odors.
  • If you don’t eat or drink for 12 hours: Your blood sugar levels can drop and/or cause dehydration. Watch for signs of dehydration such as headache and increasing nausea. Sipping fluids that contain carbohydrates may prevent these symptoms.
  • If you are taking insulin or medications to control blood sugar levels: Tell your medical team if you can’t tolerate food or beverages for 24 hours or more. You may need to have your medications adjusted to avoid a hypoglycemia (low blood sugar) episode.

You may have nausea before a treatment session or at mealtime. Remembering nausea from a previous treatment session, or from a specific food or event, can cause you to anticipate nausea. There are things you can try to prevent or lessen this feeling.

  • Practice meditation or relaxation techniques.
  • Try to change the environment with pleasing conversation, music, or an activity. Doing different things at each session can help distract you from the routine experience of your treatment.
  • Talk to your medical team about medication options that can help relieve anxiety and anticipatory nausea.
  • After an episode of vomiting, sit upright and bend forward.
  • Do not eat or drink until the vomiting is under control.
  • Try sipping on small amounts of clear liquids first, such as apple or cranberry juice, pear or peach nectar, broth (may be better tolerated if cool to warm instead of hot), flat ginger ale, or a popsicle.
  • If you are able to keep clear liquids down, try eating small amounts of crackers, toast, cereal, or noodles in broth.
  • Once you tolerate these foods, gradually reintroduce foods you normally tolerate well.
  • If you are vomiting for more than 24 hours contact your healthcare provider.

Possible causes: surgery, chemotherapy, radiation to the abdomen, certain medications, infection, food sensitivity, and stress.

Diarrhea can lead to dehydration and nutrient loss. Always bring it to the attention of your medical team.

If you have diarrhea:

  • Aim for a minimum of 8 cups of liquids daily. You must drink fluids to prevent dehydration.
  • We recommend beverages such as water, diluted fruit juices, broth, and decaffeinated coffee or tea.
  • Liquids at room temperature or warmed are best: avoid very cold or very hot beverages.
  • Eat small, frequent meals to help your body absorb nutrients.
  • Try low fiber foods (mashed potato, white rice, noodles, or low-fiber bread and cereals made from refined grains), soft cooked vegetables, canned or peeled soft fruits (banana, applesauce), skinless chicken and turkey, lean beef, cooked fish, and cooked eggs.
  • Avoid gas-forming foods and beverages, such as beans/legumes, onions, carbonated beverages and chewing gum.
  • Avoid greasy, fatty, or fried food as well as spicy foods.
  • Avoid alcohol and caffeine.
  • Avoid large portions of mild and dairy products.
  • Avoid rich desserts.
  • Avoid sugar-free candies and gums that contain sugar alcohols (ingredients such as sorbitol, mannitol or xylitol) or other sugar substitutes, which may have a laxative effect.
  • If your diarrhea is oily or greasy in appearance, you may be having trouble digesting fats. Bring this to the attention of your medical team. They may want to prescribe digestive enzymes to relieve these symptoms.
  • Take anti-diarrhea medications as prescribed by your doctor.

If you were able to have milk and dairy products before you began chemotherapy or radiation treatment, but now you get gas, abdominal cramping, and diarrhea after you have them, you may have developed lactose intolerance.

It is not uncommon for cancer treatments to reduce your intestinal tract’s ability to make the enzyme (lactase) that digests the carbohydrate in milk (lactose). This may be a temporary condition.

Tips to reduce symptoms:

  • Avoid large portions of milk and dairy products: some people with lactose intolerance can tolerate small amounts without difficulty.
  • Milk and ice cream because they have the highest amount of lactose among dairy products. Aged cheeses, yogurts and non-dairy milk options such as soy or almond milk may be easier for you to digest.
  • Lactaid® or other lactase enzymes in the form of pills, capsules, or liquid are available at pharmacies and grocery stores. You do not need a prescription.
  • Without dairy products, you may need to consider calcium-fortified foods and beverages to help meet your calcium requirements. Ask your medical team or Registered Dietitian Nutritionist to help you decide if a calcium supplement is right for you.

Possible causes: certain cancer treatments, pain medications, dehydration or poor fluid intake, lack of fiber in your diet, and lack of physical activity.

If you are unable to pass stools and have nausea, vomiting, or abdominal pain or swelling, alert your medical team. This combination of symptoms may indicate something more serious, and your doctor needs to know about it.

If you have constipation:

  • Drink at least 8 cups of fluid a day to help keep stools soft. Water, prune juice, warm juice, decaffeinated tea, warm broth, and warm lemonade are good choices.
  • Increase your fiber intake by choosing more fruits, vegetables, whole grains, beans, legumes, and nuts.
  • Consider a fiber supplement if eating a diet with more fiber does not improve your bowel regularity.
  • Avoid inactivity: Moving around for a few minutes every hour during the day, and taking a walk every day can help with bowel motility. Talk to your medical team before starting a new exercise.

Possible causes: certain medications (prednisone), nutritional deficiency, or a medical condition.

If you notice fluid retention (water weight), rapid weight gain, or both, tell your medical team.

Do not reduce your fluid intake without speaking to your doctor – this could result in dehydration. Instead, let your doctor determine the cause and advise you on what to do.

If you are retaining fluid:

  • Continue to drink. (Only restrict your fluid intake if your doctor specifically tells you to do so.)
  • Avoid processed foods that are high in sodium. (The sodium content of foods is listed on the labels. The average person should aim for less than 800 milligrams (mg) of sodium per meal, if eating 3 meals per day.)
  • Be as physically active as possible.

Talk to your doctor about medication to help reduce fluid retention.

Possible causes of weight gain during cancer treatment:

  • Fatigue
  • Decreased physical activity
  • Medication side effects
  • Eating more due to feelings of stress or depression
  • Chemotherapy-induced hormone changes that alter your metabolism or thyroid function
  • Fluid retention/swelling

If you are unintentionally gaining weight but you are not retaining fluid, try these tips.

  • Eat when you are truly hungry. Before you reach for food, ask yourself “Am I really hungry?” This “mindful” approach to eating can help you avoid consuming extra calories for comfort, out of boredom, or for other emotional reasons. Make a list of activities you enjoy and refer to it when you find yourself wanting to eat simply because you are bored.
Talk to your medical team about the integrative care options available in our outpatient centers to help you cope with your feelings or stress in a healthier way.
  • Portions are important. Get the measuring cups out and learn what a standard serving size looks like on your favorite plate, bowl, or cup.

Examples of what a standard serving size looks like:

  • 3 ounces of meat = a deck of cards or size of your palm
  • 1 ounce of cheese = a pair of dice
  • 1 cup vegetables = a clenched fist
  • ½ cup pasta = the front of your clenched fist
  • 2 Tablespoons of hummus or nut butter = a golf ball

Avoid eating foods out of a package. Put food on a plate or in a bowl to help you visualize the proper serving size, and then put the rest of the package away.

If you want to lose weight while receiving cancer treatment, talk to your doctor FIRST. There are limits to how quickly you should lose weight and the total amount of weight that can be lost safely. This is especially true in the pre-treatment and active treatment phases for cancer patients.

Talk about your weight goals, and what you want to do to achieve your goals before you begin a weight loss plan.

Your medical team needs to evaluate the safety of your plan as it relates to your cancer diagnosis and treatment, and monitor you closely throughout the process.