# Cancer Nutrition: How to Keep Your Strength

> How to maintain strength during treatment: cancer nutrition, body support, Dr. Wydoff’s advice and safety rules.

- URL: https://celitel.online/en/blog/pitanie-pri-onkologii/
- Author: Dr. Boris Wydoff — https://celitel.online/en/about/
- Published: 2026-10-14
- Language: en

Cancer nutrition helps support the body’s strength during treatment and recovery. Right now, it is important not to look for a “miracle diet,” but to maintain an adequate intake of nutrients, consider a person’s condition and food tolerance. Loss of appetite, weakness and weight loss can occur because of the disease or treatment, so dietary changes are best discussed with a doctor.

During treatment, the body faces an additional burden. It needs energy, protein, fluids, vitamins and minerals to maintain normal functions and recover after medical procedures. Proper nutrition does not replace prescribed therapy, but it can be part of caring for a person’s condition.

Before using any herb, supplement or changing your diet — tell your oncologist.

## Why does the attitude toward food change during treatment?

During cancer treatment, usual eating habits can sometimes become difficult. A person may have less desire to eat, become tired more quickly, notice changes in the taste of foods or experience difficulty swallowing.

Doctors associate these problems not only with the disease itself but also with the effects of treatment. Chemotherapy can cause nausea, vomiting, dry mouth, changes in taste, diarrhea or constipation. Some medications affect rapidly renewing cells of the mucous membranes, which can lead to unpleasant sensations in the mouth and throat, as well as pain when eating.

Radiation therapy in certain areas of the body can also affect the ability to eat normally. For example, when the head and neck area is treated, dry mouth, taste changes and swallowing difficulties may occur. Treatment in the abdominal area can lead to problems with intestinal function.

When food intake becomes insufficient, the body may receive less energy and protein than it needs. This can lead to weight loss and weakness. That is why cancer nutrition is not chosen according to general rules, but with consideration of a person’s condition, type of treatment and food tolerance.

Sometimes an approach considered beneficial for a healthy person needs to be changed during treatment. For example, people without illness are often advised to limit calories, while during active treatment maintaining weight and receiving enough nutrients may be more important.

The goal of nutrition during this period is not to create additional restrictions, but to help the body receive the resources it needs along with prescribed therapy.

## How can you understand that nutrition needs special attention?

Signs of nutrition problems can vary. A person may start eating noticeably less than usual, lose weight, feel full after a small portion or experience unpleasant sensations while eating.

Appetite can also be affected by fatigue, anxiety, pain and emotional state. Some people find that their favorite foods begin to smell or taste different. Sometimes food becomes less appealing because of changes in taste perception.

It is important to pay attention not only to the amount eaten, but also to changes in overall condition:

- clothes become noticeably looser;
- strength and endurance decrease;
- it becomes difficult to perform usual daily activities;
- there is a feeling of constant tiredness;
- preparing and eating food becomes difficult.

At the same time, conclusions should not be made based on only one sign. Loss of appetite or weakness alone does not indicate the cause of a condition. A doctor determines the diagnosis and evaluates the situation after an examination and necessary tests.

When appetite decreases, specialists usually advise discussing nutrition with the treating doctor or a dietitian. This helps choose a suitable diet and notice a lack of important nutrients in time.

### How to make eating easier in everyday life

During treatment, it is useful to prepare conditions that make eating easier. You can:

- keep foods at home that do not require long preparation;
- prepare meals in small portions;
- freeze prepared food so you do not have to spend energy cooking every day;
- ask loved ones for help with shopping and cooking;
- choose times for meals when you feel better.

Sometimes it is easier to eat more often but in smaller portions. If a large plate feels overwhelming, several small meals throughout the day may be easier to tolerate.

## What can be changed in the diet during treatment?

Nutrition during cancer treatment is often built around a simple goal: to provide the body with enough energy and nutrients. Depending on the situation, a person may need foods containing protein, calories, vitamins, minerals and enough fluids.

Protein is especially important for maintaining body tissues. Sources can include animal-based and plant-based foods — the choice depends on individual tolerance, health condition and doctor’s recommendations.

If regular food is difficult to eat, doctors may sometimes recommend making nutrition more convenient: choosing foods that are easier to tolerate, preparing small portions in advance and using help from loved ones.

In some situations, cancer nutrition differs from the usual idea of “the healthiest food.” During treatment, a person may need more protein and energy than someone without illness.

Do not switch to strict restrictions, fasting or so-called cleansing programs on your own. During treatment, the body often needs a stable supply of nutrition. Before using any herb, supplement or changing your diet — tell your oncologist. You should not change prescribed treatment or medications yourself.

## What I recommend … for cancer and restoring strength

I, Dr. Boris Wydoff, have studied the influence of nutrition, movement and lifestyle on a person’s condition for more than fifty years. In cancer, I view nutrition as support for the body’s strength and as a way to treat yourself with care during a difficult period.

My observations: during serious treatment, people are often helped not by searching for one “main food,” but by returning to simple daily habits — understandable food, routine, movement according to their abilities and a calm attitude toward their condition.

**Bring more living foods back to your plate.** In my books, I write that vegetables and greens should have an important place in natural nutrition. I associate “living” food with receiving a simpler and more natural diet. In my experience, calm and understandable nutrition helps maintain a sense of support during recovery.

Vegetables can be added gradually, depending on tolerance. If there are intestinal problems, pain, diarrhea or other symptoms, the approach should be discussed with a specialist.

**Remove what overloads your diet.** I recommend paying attention to excess sugar, white flour and heavily processed foods. In my books, I explain it this way: the body needs strength not for an extra burden from heavy food, but for recovery. This is my view, based on my observations of people’s nutrition.

At the same time, during cancer treatment, nutrition should not become a strict system of prohibitions. If a person has difficulty getting enough calories and protein, a doctor may recommend a more nutritious diet.

**Use vegetable juices as an addition to your diet.** I have written about fresh vegetable juices as part of my approach. I associate them with the desire to give the body an easier way to receive nutrients. In my system, there are combinations of carrot with beetroot and cucumber, as well as carrot with spinach.

Juices are not an essential part of nutrition and do not replace treatment. Before drinking juices with certain health conditions, while taking medications or during therapy, you should discuss this with your oncologist.

**Maintain movement and warmth in everyday life.** I believe that walks, moderate activity and caring about warmth help support a person’s overall condition. In my books, I connect movement with maintaining vitality and well-being.

Even a short walk within your abilities can become part of your daily routine. However, the level of activity should match your condition and your doctor’s recommendations.

I have also written about separate food combining as my approach to combining foods. Doctors do not consider food separation a necessary condition for nutrition in cancer, but I view it as part of my perspective on lighter eating. All dietary changes during treatment should be discussed with your doctor.

## Small practical steps to maintain strength

During treatment, it is useful not to try to change everything at once. Gradual introduction of habits is often more sustainable. You can start with simple actions:

- drink enough fluids if your doctor has not prescribed restrictions;
- plan shopping in advance;
- add a source of protein to suitable meals;
- choose foods that are easier to tolerate;
- write down changes in appetite and well-being to tell your doctor.

If you feel worse after eating, it is useful to note which foods cause discomfort. Such records help the specialist better understand the situation.

## How is cancer nutrition different from nutrition for other conditions?

Many people wonder how diet changes with different illnesses. For example, nutrition for gastritis usually takes into account food tolerance and stomach condition, while nutrition for pancreatitis requires special attention to pancreatic function. Such restrictions cannot automatically be applied during cancer treatment.

When cancer is combined with other conditions, the diet should be chosen by a doctor. For example, nutrition for insulin resistance may require monitoring the composition of the diet and the amount of carbohydrates, but during cancer treatment the main goal remains receiving enough energy and nutrients.

Nutrition for anemia also depends on the cause of reduced hemoglobin levels and a person’s overall condition. Sometimes additional correction is needed under specialist supervision.

## What should not be done during chemotherapy without a doctor’s permission

During chemotherapy, any supplements and major dietary changes should be discussed with an oncologist. Some common foods and substances may affect treatment. Without a doctor’s permission, you should not use St. John’s wort or grapefruit, as they can change the concentration of some anticancer medications in the body. You should not take high doses of antioxidants during chemotherapy or radiation therapy on your own. Concentrates and herbal extracts should also not be used without consulting a specialist.

Regular vegetables and fruits are not prohibited foods. It is important to follow food safety rules, especially if treatment lowers the body’s defenses. When immunity is reduced, a doctor may separately explain food preparation rules and foods that are better avoided temporarily because of infection risks.

## Can you follow a weight-loss diet during cancer treatment?

During treatment, the goal of nutrition usually differs from ordinary weight loss. If a person loses appetite or weight, the goal may be the opposite — maintaining sufficient energy intake.

Therefore, a diet to lose weight should not be started independently during cancer. Any restrictions should be discussed with a doctor who considers treatment and the person’s condition. Even restrictions that are useful in another situation may be unsuitable if the body currently needs more resources for recovery.

## How to choose cancer nutrition considering age and goals?

The diet depends on a person’s condition, so nutrition for children with cancer requires separate specialist monitoring. A child’s needs for energy and nutrients differ from those of adults, and dietary changes should be supervised by a doctor.

Adults should also consider their goals. For example, nutrition for building muscle mass during treatment can only be considered according to health condition, tolerance to exercise and recommendations from the medical team.

## When to see a doctor

### Seek medical help urgently

During chemotherapy, a temperature of 38 °C or higher or chills require immediate contact with your oncologist. Do not try to reduce fever on your own before receiving medical advice. Urgent medical evaluation is also needed for shortness of breath, chest pain, leg swelling, vomiting lasting more than a day or inability to drink. Do not delay seeking help in case of blood in stool or vomit, black stool, fainting or severe heart palpitations.

### Discuss your condition with a doctor as planned

Contact a specialist if you experience a significant decrease in appetite, weight loss, difficulty eating or a feeling that your usual nutrition has become impossible. It is helpful to tell your doctor in advance:

- how much weight you have managed to maintain or lose;
- which foods have become difficult to tolerate;
- whether there is nausea, vomiting or bowel problems;
- how much fluid you are able to drink;
- whether swallowing difficulties have appeared.

A doctor will help understand the cause of changes and choose support. It is especially important to report any new symptoms during treatment.

More about how I work with this topic can be found on the page “[Oncology](/health/onkologiya/)”.

## From the editorial team

This article was prepared using the books of Dr. Boris Wydoff and medical reference materials about nutrition during treatment. The material does not replace a doctor’s consultation and does not cancel prescribed therapy.

Medical information: [NCI (National Cancer Institute of the USA)](https://www.cancer.gov/about-cancer/treatment/side-effects/appetite-loss/nutrition-pdq), [NCI (National Cancer Institute of the USA)](https://www.cancer.gov/about-cancer/treatment/side-effects/appetite-loss).

## FAQ

**Q: Cancer nutrition: what should you eat during treatment?**
A: Nutrition is selected based on your condition, appetite and recommendations from your treating doctor.

**Q: Can you change your diet during cancer on your own?**
A: Any major changes are best discussed with your oncologist.

**Q: What should you do if you have no appetite?**
A: Discuss the problem with your doctor and choose a convenient way to receive nutrition.

**Q: Which foods are important during cancer?**
A: Usually, attention is paid to getting enough nutrients, protein and fluids.

**Q: Can you drink juices during cancer treatment?**
A: Fresh juices may be part of the doctor’s approach, but dietary changes should be discussed with a specialist.

**Q: Do you need to avoid fruit during treatment?**
A: Regular fruits are not prohibited unless your doctor gives other recommendations.

**Q: Can diabetes nutrition be combined with cancer treatment?**
A: When diseases occur together, nutrition should be selected individually with a doctor.

**Q: How can you maintain strength during chemotherapy?**
A: It is important to monitor nutrition, tell your doctor about eating problems and follow prescribed treatment.

**Q: Can you fast during cancer treatment?**
A: Fasting and strict restrictions without a doctor’s permission are not recommended during treatment.

**Q: Can you change nutrition for gastritis or pancreatitis during treatment?**
A: When cancer is combined with gastritis or pancreatitis, nutrition should be discussed with a doctor because restrictions depend on a person’s condition.

**Q: How can you build muscle mass during treatment?**
A: Building muscle mass requires sufficient nutrition and appropriate physical activity, but the plan is best created together with a specialist.


_Educational content; it does not replace medical advice._