Diet For Oncology Patients

Malign diseases are a significant problem of public health. They are the second most important cause of death behind cardiovascular diseases. Thanks to the possibilities of early detection of malign diseases, survival rate has grown for about 20% when compared to the 70s and malign disease is nowadays considered a chronic disease.

Guest author: Margareta Benković, msc
Nutritionist at the Centre for Nutrition Counseling
Centre for psychological assistance of Association of women affected by cancer EVERYTHING for HER*

Considering the fact that around 35% of diagnosed tumors in men and up to 60% in women can be linked to diet, it is no wonder this topic raises attention and interest of those affected by a disease. Changes to diet can be made already today.

People affected by malign diseases can be divided into those in the process of initial treatment, and those living with cancer after the initial treatment. The second group includes those that no longer have the disease after the treatment, those who continue to take medications to reduce the risk of relapse, and those whose disease is under control, showing little symptoms but undergoing treatment for malign disease as a chronic disease.

A third of deaths caused by malign diseases can be linked to diet and lifestyle habits such as poor diet, physical inactivity, drinking and smoking, being overweight and obese.

There can be no list of factors that help protect the health, prevent disease, and develop a healthy lifestyle without a balanced diet and maintained body weight during the entire life. During treatment and recuperation from malign diseases, a proper diet is very important – adjusted to the physical state, treatment phase, and reaction to therapy. Under pressure from disease, patients often seem more than willing to make drastic changes to diet which, if not balance, won’t bring any benefits. Proper diet does not necessarily ask for drastic changes but for adjustment to the current state and needs of the organism.

Some of the most common questions and problems those affected by malign diseases have:     

  • Which foods can I and cannot I eat?
  • What to take for a better immune system?
  • What to take to preserve the healthy cells during chemotherapy?
  • What to eat to raise leucocyte numbers?
  • I have no appetite.
  • I force myself to eat, because I know I have to.
  • I’m losing weight.
  • Food disgusts me.
  • I’m afraid to eat because it will feed the carcinoma.
  • I stopped eating carbs to starve the cancer cells.

There are many different professional and amateur opinions on how people affected by malign diseases should eat. There are many products on the market and it’s not always easy to recognize what makes sense to take and when, and what’s unnecessary or even has a negative effect on health.

„Sugar feeds cancer“

Saying that cancer feeds on sugar is a very simplified way of looking at it. It’s actually inaccurate because cancer progression depends on many factors. When diet is concerned, reducing sweets to a minimum is recommended to both healthy and ill people – more specifically, to see them as an occassional treat. Too much sugar is not welcome in the diet, just like too much caffeine, alcohol, or red meat. Basically, too much of anything is not good.

Those who follow the basic principles can from time to time have a treat without worry.

Diet is a very important support in treating malign diseases. Generally speaking, emphasis should be on plant-based foods, quality sources of protein, vitamins, minerals, complex carbs and quality fats – food with high nutritive value. It’s important to maintain adequate fluid intake, mostly water. Since nutritive needs are individual, it’s recommended to advise the nutritionist in order to receive recommendations created for personal needs. Patient needs to be supervised during the treatment and the diet needs to be continuously adjusted to patient’s current state and needs.

Even though diet needs to be adjusted on an individual level, these are some guidelines that can help maintain a balanced diet:

  • Try to eat mostly plant-based foods – this means you should limit the intake of animal-based products and include more fruits and vegetables
  • Raise the daily intake of fruits, vegetables and whole grains. A good common rule is to try to eat five portions of vegetables and two portions of fruit per day (e.g. a cup of broccoli is one portion). Also, try to eat more beans (kidney beans, lentils etc.) if they suit you
  • Reduce the intake of processed foods, red meat, animal fat and alcohol
  • Reduce the intake of high-calorie food, like sweet drinks, fast foods and candy or sweets
  • Limit alcohol intake (e.g. wine, beer, spirits) to max two drinks per day
  • Reduce portion size and increase the frequency of planned meals
  • Reduce the intake of snacks and the number of meals outside of the house
  • Increase the variety of foods and ensure a suitable intake of nutrients
  • Diet supplements are NOT recommended to people living with cancer without first consulting a physician

Body weight

In oncology patients, it’s very important to track body weight. Even a small loss of body weight (less than 5%) before the treatment begins is connected to worse prognosis and reduced quality of life.

Types of malign disease treatment that affect the diet are surgery, chemotherapy, radiotherapy, and immunotherapy.

During the malign disease treatment some side effects may occur, which can affect food intake, such as change in taste and smell, wounds in the mouth, dry mouth, problem swallowing, chronic fatigue, vomiting, diarrhea, constipation, pain, depression, anxiety, and can lead to malnutrition which will result in reduced ability to fight infections.

Loss of body weight and malnutrition are present in most patients and around 20% of patients die from malnutrition, not the disease itself.

Patients with lung cancer and gastrointestinal system cancer (stomach, colon, rectum, liver, pancreas) have the highest risk of malnutrition.

Some malign diseases, especially pancreas and stomach cancers, cause severe cachexia, and patients lose up to 10-20% of body weight. Primary cause of tumor cachexia is a complicated metabolic state which has hypercatabolism in its base. Protein synthesis is reduced, and their decomposition is enhanced. Standard nutritive support will not stop physical degradation in the syndrome of tumor anorexia and cachexia. Applying megestrol acetate and enteral diet with enhanced EPA intake of 2,2 g/day for 8 weeks is a beneficial therapeutical combination for patients with severe tumor anorexia and cachexia.

Consequences of malnutrition are increased risk of complications, reduced effect and tolerance of treatment, reduced quality of life, lower survival rate, and high treatment costs.

Consuming appropriate meals and food types before, during and after the treatment cycle of malign diseases can help the patient maintain strength, better tolerate unwanted side effects of medication and treatments, and increase the quality of life. Enteral supplements can be introduced to the diet in order to prevent weight loss or help get the lost kilos back during the treatment. Enteral supplements are prescribed by a specialist physician based on indications, and they are available in the pharmacy with a prescription.

Diet during chemotherapy

Treatment phase that includes chemotherapy is not the time for drastic changes in the patient’s diet. It’s important to eat and maintain adequate body weight. When the side effects of the treatment pass, the patient will return to their usual diet and, if necessary, gradually introduce changes so that the diet becomes balanced and adjusted to patient’s health.

Chemotherapy has many side effects that affect food intake.

Hot foods are steamy, which can be repulsive for post-chemotherapy patients that are sensitive to smells, so it’s better to eat when the food cools down. Chemotherapy often damages the mucous membrane in the mouth and leads to dryness, so very firm foods should be avoided so as to not create further complications. Due to possible change in taste and smell some foods don’t sit well with patients, so they need to force themselves to eat it. With nausea, vomiting and diarrhea, it’s recommended to eat small meals often, and the intake of lightly cooked foods, as well as fluids and electrolyte intake.

It’s important to regulate body weight. If you notice weight loss, food intake is not sufficient, and nutritionist and physician need to intervene.

Supplements during chemotherapy

Due to a large number of diet information, especially on supplementation, patients are often bombarded with advice on what they must/should take in order to get better.

If they don’t get a quality advisor for diet, their day is spent eating and drinking, which can be redundant.

If you don’t have a specific gastrointestinal problem, food intolerance, diabetes, or some other disease that calls for a special diet regime, stick to recommendations for the general public.

If the side effects are average, normal and diverse diet is expected to maintain the organism in good shape so that the therapy can be received on schedule. Supplements are necessary if and when insufficient intake of food occurs. Several days before and after chemotherapy, supplements are not recommended. If you decide to take any, consult a physician prior. Never take more than one at the same time, because, for most supplements, it’s unknown how they act if mixed. Some research has showed that certain supplements can decrease the effect of therapy.

Fluid intake

Patients need to have adequate fluid and electrolyte intake to prevent dehydration and hypovolemia. Ascites, edema, vomiting and diarrhea result in increased loss of fluids and electrolytes. Signs and symptoms of dehydration include fatigue, acute loss of body weight, hypernatremia, dry mouth, dark urine with a strong smell, and reduced urine volume.


Proper, balanced diet, fluid intake, and maintaining adequate body weight are very important when treating malign diseases. Diet needs to be adjusted to current state and side effects, as well as satisfy energetic and nutritive needs of the patient for better toleration and results of the therapy. However, don’t expect you’ll cure the disease with diet.

*Association of women affected by cancer EVERYTHING for HER created the Centre for psychological help for women affected by cancer. Through educational workshops as well as individual and group work with users, dietary topics take a significant place which is why the centre for diet counseling has been formed so that affected women can receive advice from a nutritionist about an individual diet system, adjusted to personal needs and possibilities.