Effects of Chemotherapy on the Digestive Tract

The side effects of chemotherapy treatment can be overwhelming. Some of the side effects of chemotherapy can include nausea, vomiting, diarrhea, and constipation. The good news is that all of these side effects are temporary and very treatable.

Woman receiving chemotherapy
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Nausea and Vomiting

Nausea and vomiting are side effects that are a common concern for chemotherapy patients. There are new drugs that can now eliminate or diminish these side effects. Contact your healthcare provider if nausea and vomiting are not being helped by the medication, or if you can't keep even liquids down.

Here are some tips that may help control these symptoms:

  • Before chemotherapy treatment, try eating a light meal.
  • Concentrate on breathing slowly and deeply when feeling nauseated.
  • Drink plenty of liquids, or suck on ice chips, but do so an hour before or after mealtimes.
  • Eat several small meals throughout the day instead of three large ones.
  • Eat and drink slowly, chewing well.
  • Eat foods cold or at room temperature to avoid being bothered by strong odors.
  • Eating foods like cereal, toast, and crackers before getting up out of bed can help with morning nausea. This is not recommended for anyone with mouth and throat sores, or who has trouble producing saliva.
  • Rest as you need to, but don't lie flat for at least 2 hours after a meal.
  • If you get nauseous during treatment, try fasting for a few hours before.
  • Keep busy to distract yourself from nausea by watching TV, talking with friends and family, or working on hobbies.
  • Suck mints or tart candies (again not recommended for anyone with mouth or throat sores).
  • Take anti-nausea medication 30 minutes before eating a meal.
  • Try to avoid foods that are fatty, fried, or sweet.
  • Try drinking clear unsweetened fruit juices (such as apple or grape), and light-colored sodas that have lost their fizz (gone flat).


Chemotherapy can affect the cells that line the intestine, and diarrhea may be the result. If diarrhea is troublesome, doesn't clear up in 24 hours, or is accompanied by pain or cramps, talk to your healthcare provider. Don't take over-the-counter diarrhea medicine without talking to your practitioner first. If the diarrhea is severe, your healthcare provider may prescribe some medication, or recommend intravenous fluids to avoid dehydration.  

Here are some tips to keep diarrhea at a minimum:

  • Drink plenty of fluids at room temperatures such as water, broth, sports drinks, or ginger ale to keep from getting dehydrated. Remember to sip them slowly.
  • Eat foods that are low in fiber such as white bread, white rice or noodles, creamed cereals, ripe bananas, canned or cooked fruit without skins, cottage cheese, yogurt without seeds, eggs, mashed or baked potatoes without the skin, pureed vegetables, chicken, or turkey without the skin, and fish.
  • Eat several small meals throughout the day instead of three large ones.
  • If you're lactose intolerant, avoid milk products.
  • Keep your potassium level up by eating bananas, oranges, potatoes (boiled or mashed), and peach and apricot nectars (as long as they are on the diet plan given to you by your healthcare provider).
  • Stay away from coffee, caffeinated tea, alcohol, sweets, and fried, greasy, or spicy foods which can make diarrhea worse.
  • Stay away from high fiber foods such as whole grain bread and cereals, raw vegetables, beans, nuts, seeds, popcorn, and fresh and dried fruit.


Some medicines, such as opioid pain medication, can cause constipation. Low amounts of physical activity and a lack of fluids and fiber in the diet can also contribute to constipation. If you go a day or two without moving your bowels, call your healthcare provider and follow any instructions you are given.

Here are some other tips for avoiding constipation:

  • Ask your practitioner about taking medicine and if it's possible for you to increase the fiber in your diet. Examples of high fiber foods are bran, whole-wheat bread and cereals, raw or cooked vegetables, fresh and dried fruit, nuts, and popcorn.
  • Avoid cheese, chocolate, and eggs which can cause constipation.
  • Check with your healthcare provider about starting an exercise program, or try taking a walk every day.
  • Drink lots of fluids, including water and warm or hot liquids.
8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Cancer Society. Chemotherapy Side Effects.

  2. American Cancer Society. Nausea and Vomiting Caused by Cancer Treatment.

  3. Managing Nausea and Vomiting at Home. American Cancer Society.

  4. McQuade RM, Stojanovska V, Abalo R, Bornstein JC, Nurgali K. Chemotherapy-Induced Constipation and Diarrhea: Pathophysiology, Current and Emerging TreatmentsFront Pharmacol. 2016;7:414. doi:10.3389/fphar.2016.00414

  5. American Cancer Society. Diarrhea.

  6. Neefjes ECW, van der Wijngaart H, van der Vorst MJDL, et al. Optimal treatment of opioid induced constipation in daily clinical practice - an observational studyBMC Palliat Care. 2019;18(1):31. doi:10.1186/s12904-019-0416-7

  7. National Cancer Institute. Constipation: Cancer Treatment Side Effect.

  8. National Institute on Aging. Concerned About Constipation?

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.