Nutrition Considerations During Cancer Treatment

By Jean LaMantia, RD

Compared to most people, I was extremely well qualified to make decisions about proper nutrition during cancer treatment: I had a Bachelor’s degree in applied human nutrition and I had completed a clinical dietetic internship at a busy teaching hospital. I’d even had a job that included some time with inpatient cancer patients! Still, when diagnosed with cancer myself, I felt completely unqualified as to which diet I should follow and which supplements, if any, to take.

My first challenge with nutrition came with my first chemotherapy treatment. I was warned that I might experience nausea afterwards so I choose my last supper carefully. I didn’t want to choose my favourite food — pasta — for fear that I would be forever turned off of it. So, I chose something that I enjoyed, but could live without ever eating it again (and probably be better for it)… a McDonald’s filet-o-fish.

Chemotherapy is chemical therapy — essentially drugs, administered either through IV or pills. The type of chemotherapy that you receive will be different based on your specific type of cancer and other considerations. Not all of them make you sick, but mine certainly did. After that filet-o-fish, I didn’t eat another thing for 8 days. I’m not exaggerating. The tray would come up to my hospital room and I couldn’t lift the lid off, knowing that the smell would send my stomach into painful heaves.

The staff who picked up my untouched trays would remark “You haven’t eaten anything, you should eat!” This started to stress me out, to the point where when my oncologist came into my room and asked how I was doing, I replied in a panicked voice “I’m not eating anything!” He was very reassuring, and said: “Don’t worry about it, just drink”. That advice eased the fear and anxiety that was building in me with each untouched meal, and I have since repeated it to my own clients many times.

Drink Up!

If you are going through treatment, make this a goal for yourself: maintain your hydration [1]. Why is this so important? First off, the chemo drugs need to leave your body and they get processed through the liver and kidneys then exit the body through the urine, sweat, and feces [2].

Another important reason is that when you get dehydrated, you get constipated, when you get constipated your nausea gets worse, when nausea is worse, you eat and drink less, which leads to more dehydration. I call this the vicious cycle. You need to break this cycle by drinking and keeping yourself hydrated.

Is There a Cancer Diet?

Your nutrition needs during treatment either chemotherapy, radiation, or surgery are symptom-driven. For example, you may experience altered taste, dry mouth, nausea, vomiting, constipation, diarrhea, high blood sugars, low blood sugars, poor appetite, increased appetite, weight loss, weight gain… well, you get the idea. Your diet needs to be adjusted to help treat whatever symptom you are experiencing. In this way, the diet during treatment is not one-size fits all.

If you are not having many symptoms (or side-effects) to speak of, then you can complement your cancer therapy by choosing a cancer risk reduction diet. This is generally what people think of when they think of a “cancer diet”. This is a diet that consists primarily of plant foods, with an emphasis on unprocessed foods.

What About the Diet of the Day?

There are many diets that you can find on the Internet that claim to cure cancer. Do they? As a registered dietitian, I can’t in good faith recommend any diet as a cure for cancer, as none has been scientifically proven to do so as of now.

By scientifically proven, I mean using the scientific method, which involves developing a hypothesis and setting up an experiment to test it. The experiment needs to include a sufficient number of people, so that you can be fairly certain that the results are not just a fluke. Ideally, the study is also done repeatedly, so you can demonstrate that the results are reproducible. This just hasn’t ever been the case with any diet yet.

Of course, there are websites out there that will really test your resolve — or, as I like to say, “mess with your head” — because of their use of very compelling testimonials. These captivating first-person accounts of people sharing their story, and saying they managed to cure cancer through their diet alone without any other cancer treatment, can certainly get you to question your choice to proceed with a conventional cancer treatment plan.

Here’s my advice: if you find yourself being tempted by anything that sounds too good to be true, do more research. Try to be thorough and unbiased, and search out phrases like “the downside to…” or “the problem with…” or “why ____ doesn’t work”. Recognize your own bias, try to keep it under control, and see if you can talk to a real person who has undergone what you’re looking into.

Getting the Whole Story

I remember talking to a woman who told me how the Budwig protocol was working for her mother. This woman couldn’t believe how well her mother was doing because her prognosis wasn’t that good. The entire family was amazed at how well she was doing.

I was intrigued with this: could this be an actual encounter with a person whose mother used diet to treat their cancer? I kept asking more about what her mother was doing and specifics about the protocol. During my enthusiastic questioning, the daughter eventually mentioned that the mother was still undergoing chemotherapy.

So, while her mother was on a proven chemo regime, the daughter continued to be convinced and to tell others that the key to her survival was her diet. Had I not probed more and asked more questions, I might have taken her initial testimonial at face value.

Too Good to Be True?

There are a couple of red flags that you should keep in mind. If you read that “your doctor knows about this but refuses to use it, as it would put him out of business” or anything of the same sentiment, walk away. Oncologists are healers who studied medicine to help people. If you don’t trust your doctor, then by all means get a different one, but don’t believe these conspiracy theories.

If there really was a diet that could cure cancer without the need for other treatment, we would know about it, and it would be prescribed to you.

Please know that there isn’t just one way to go through cancer treatment. While working with a doctor whom you trust is key, everyone has their own path. While you might be drawn to complementary therapies, others may want to do strictly what the doctor has ordered and nothing more. It’s your decision. While you certainly don’t want to throw your money away on fake cures — or worse, interfere with a reliable treatment — I understand the desire to research what else you can do to complement your cancer treatment. Just be sure to keep your cancer care team in the loop about what you are doing.

Can Food Really Make A Difference?

I believe food can help you to manage the symptoms of cancer and of its treatment. After treatment is finished, there is evidence to support that making changes to your diet and lifestyle may reduce your risk of recurrence or of developing a new cancer [3]. These changes work through a variety of channels, including supporting your immune system, reducing chronic inflammation, and acting on cancer cells directly. By working with a registered dietitian who can help get you on the right path to healthy eating after cancer, you will feel better knowing that you are doing everything you can to be cancer-free.

Helpful Resources

Oncology Nutrition — Academy of Nutrition and Dietetics

American Institute for Cancer Research

Memorial Sloan Kettering Cancer Center

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About the author:  Jean LaMantia, RD

Jean LaMantia is a Cancer Survivor, Registered Dietitian, Best Selling Author of The Essential Cancer Treatment Nutrition Guide and Cookbook. She serves cancer patients and survivors with her one-on-one counseling and public talks. Learn more at or email her directly at [email protected]


  1. National Cancer Institude, Eating Hints Before, During and After Cancer Treatment.
  2. Dana-Farber Cancer Institute, How Long Does Chemotherapy Stay in Your Body?
  3. American Institude for Cancer Research, Cancer Preventive Diet Model Plate.

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