top of page
  • drkaycierosen

What should I eat during Chemotherapy?

Updated: Feb 7

It almost seems rude to put the words "eat" and "chemotherapy" in the same sentence. Chemo is notorious for causing all sorts of problems related to food. Nausea, heartburn, and digestive problems are pretty much standard for anyone during this time. Food can smell and taste weird and things that you normally love can become downright intolerable during chemo. So when we talk about eating during chemo, the goal is to keep your body healthy in the midst of managing symptoms.

*Before making any dietary decisions, please speak with your oncology team to make sure your diet plan is appropriate for you!

Weight Changes and Chemotherapy

Before I mention any diet strategies, I want to talk about weight changes during chemo. You may gain or lose weight depending on your situation, which plays a big role in how you structure your diet. For some cancer patients, a tumor that is growing can cause weight loss, which we generally want to avoid. In this case, eating whatever you can tolerate and keep down is the goal! Nutrient dense, high-calorie food is top priority to keep your weight stable. If you fall into this category, just make sure to keep your calories up to prevent further weight loss.

However--for many women going through chemo for breast cancer, the treatment itself causes weight gain. This is not discussed frequently, but it is very common. Especially for women who have already gone through surgery for a single tumor that has not spread and are now going through chemo just to prevent recurrence, the drugs themselves can cause problems with blood sugar and lead to increased weight. This is hard on the heart, can contribute to prediabetes and diabetes, and be a particularly frustrating side effect of treatment. In this case, just "eating whatever you can" is less crucial, and eating to optimize your health and minimize side effects becomes top priority.

The goals of eating during chemo: feel better, heal faster.

  1. Minimize side effects from chemotherapy

  2. Optimize the efficacy of your chemotherapy

  3. Heal up faster

Minimizing Digestive Side Effects

Minimize effects on your mouth, stomach and intestines.

Our food travels through our body in one connected tube--starting with the mouth, and then moving to the esophagus, stomach, small intestine, large intestine, then out the rectum as stool. Any part of that tube is part of the digestive system. Because our digestive tract is constantly interacting with food, breaking it down, absorbing nutrients, and moving things along, the cells that line your digestive tract are constantly being replaced with new cells. The point of Chemotherapy is to destroy new cells--which is how it gets rid of cancer--so it has the most profound effects on the most rapidly dividing cells in the body, which includes the digestive tract. So any part of the digestion is likely to be affected. It is extremely common to experience sores in the mouth and esophagus, heartburn, and diarrhea or constipation.

The primary ways to minimize these symptoms are to limit the amount of chemotherapy drugs that reach the cells and minimize any irritation to the digestive tract. This is done in two ways:

  1. Decrease the amount of chemo to the cells in the digestive tract:

    • Cold! IV chemo drugs travel through the bloodstream to get to all the cells in the body. If you decrease blood flow to an area, there will be less chemo reaching that area! One easy way to do this is by making it very cold so no blood will flow there. If you suck on ice or eat a frozen smoothie during your infusion, it will limit blood flow to the mouth and esophagus and can prevent mouth and throat sores. This can make a HUGE difference! *Ask your doctor if you are receiving any drugs that can cause mouth sores.

  2. Minimize or eliminate foods that can irritate the gut! This includes:

    • acidic foods

    • fatty meats and dairy (including milkshakes!),

    • Fried foods and BBQ

    • raw vegetables

    • Anything you know bothers your digestion normally

The benefits of limiting calories during chemo

As I mentioned above, for some people going through cancer treatment there can be unintentional weight loss because the cancer itself is consuming so many calories. Especially if you are feeling crummy because of your treatment, in this case it is important to just eat whatever you can get down in order to keep weight up. However, on the other side of this it can actually be quite useful to limit calories around your chemo treatment. A growing number of studies are emerging that show caloric limitation through either modified fasting or a ketogenic diet can help decrease side effects, speed healing, and improve how effective the chemotherapy regimen can be.

One of the primary goals of chemotherapy is to destroy rapidly growing cancer cells. Because cancer cells grow so fast, they use a lot of calories and energy. This is one of the reasons people with growing cancers tend to lose weight without trying. These cells lack the genetic code that would normally tell them to stop growing at the appropriate time.

Having limited calories is one trigger that tells the normal cells in our body to slow their metabolism. It’s the body’s strategy for coping with limited food supply. Basically–if there isn’t a lot of food, our bodies know to slow down our use of the food we have. However, cancer cells do not have this built in mechanism–they go on chugging away and eating everything in sight. We can capitalize on this by eating less on the days around chemotherapy and intentionally slowing the metabolism of our healthy cells. This means that less of the chemo drugs will go to the healthy cells in our organs and will be more concentrated in any rapidly metabolizing cancer cells.

There are two benefits to this strategy: First, it hopefully means less damage to the organs that are more frequently impacted by the chemo (like the liver and heart). This can decrease side effects and speed healing up from your chemo regimen. Secondly, it hopefully will make treatment more effective because more of the chemotherapy drugs will reach their intended target, rather than being absorbed by healthy cells.

For my patients I recommend a specific diet protocol for the day before, day of, and day after chemotherapy that limits calories while keeping blood sugar relatively stable, and minimizes irritation to the mouth and digestive tract. Feel free to contact me to find out more about this and my whole comprehensive chemotherapy support program or check it out here!


Plotti F.a · Terranova C.a · Luvero D.a · et al. Diet and Chemotherapy: The Effects of Fasting and Ketogenic Diet on Cancer Treatment. Chemotherapy 2020;65:77–84

Impact of modified short-term fasting and its combination with a fasting supportive diet during chemotherapy on the incidence and severity of chemotherapy-induced toxicities in cancer patients - a controlled cross-over pilot study. Cancer. 2020; 20: 578.

Steven D. Mittelman. The Role of Diet in Cancer Prevention and Chemotherapy Efficacy. Annu Rev Nutr. 2020 Sep 23; 40: 273–297.

Stefanie de Groot, Rieneke T. Lugtenberg, Danielle Cohen, et al Fasting mimicking diet as an adjunct to neoadjuvant chemotherapy for breast cancer in the multicentre randomized phase 2 DIRECT trial. Nat Commun. 2020; 11: 3083.

Mohammed Jemal, Tewodros Shibabaw Molla, Tadesse Asmamaw Dejenie. Ketogenic Diets and their Therapeutic Potential on Breast Cancer: A Systemic Review. Cancer Manag Res. 2021; 13: 9147–9155.

Recent Posts

See All


bottom of page