Cancer Nutrition: How to Maintain Your Strength

Dr. Boris Wydoff

Cancer nutrition helps support your body's strength during treatment and recovery. Right now, it is important not to look for a “miracle diet,” but to make sure you get enough nutrients, take your condition into account, and choose foods you can tolerate. Loss of appetite, weakness, and weight loss can occur because of the disease or its treatment, so it is best to discuss dietary changes with your doctor.

During treatment, your body faces additional demands. It needs energy, protein, fluids, vitamins, and minerals to maintain normal functions and recover after medical procedures. Good nutrition does not replace prescribed treatment, but it can be part of taking care of your health.

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

Why can eating habits change during cancer treatment?

During cancer treatment, eating as usual can sometimes become difficult. You may feel less hungry, tire more quickly, notice changes in the taste of foods, or have trouble swallowing.

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

Radiation therapy in certain areas of the body can also affect your ability to eat normally. For example, radiation to the head and neck area may cause dry mouth, changes in taste, and difficulty swallowing. Treatment involving the abdomen may lead to changes in bowel function.

When you do not eat enough, your body may receive less energy and protein than it needs. This can lead to weight loss and weakness. That is why cancer nutrition should not follow general rules alone. It should take into account your condition, the type of treatment, and how well you tolerate different foods.

Nutritional needs can also depend on which organ is affected by the disease. For example, nutrition for stomach, intestinal, or pancreatic cancer may require particular attention to food tolerance, appetite, and adequate nutrient intake. For tumors affecting other organs, the approach is also determined individually rather than by following a universal anticancer diet.

Sometimes, an approach considered healthy for someone without an illness needs to be adjusted during treatment. For example, people without a medical condition are often advised to limit their calorie intake, while during active treatment, maintaining weight and getting enough nutrients may be more important.

The goal of nutrition during this period is not to create additional restrictions, but to help your body get the resources it needs alongside your prescribed treatment.

How can you recognize nutritional problems during cancer treatment?

Signs of nutritional problems can vary. You may start eating noticeably less than usual, lose weight, feel full after a small portion, or experience discomfort when eating.

Appetite can also be affected by fatigue, anxiety, pain, and emotional well-being. Some people find that their favorite foods begin to smell or taste different. Sometimes, changes in taste make food less appealing.

Pay attention not only to how much you eat but also to changes in your condition:

• Your clothes become noticeably looser;
• Your strength and endurance decrease;
• Everyday household tasks become difficult;
• You feel constantly tired;
• Preparing and eating food become difficult.

However, you should not draw conclusions based on a single sign alone. Loss of appetite or weakness does not, by itself, reveal the cause of your condition. A doctor assesses the situation and makes a diagnosis after an examination and any necessary tests.

When appetite decreases, specialists generally recommend discussing nutrition with your treating doctor or a dietitian. This can help you find a suitable diet and identify shortages of important nutrients in time.

How to make eating easier in everyday life

During treatment, it can help to prepare things in advance so that eating becomes easier. You can:

• Keep foods at home that do not require lengthy preparation;
• Prepare meals in small portions;
• Freeze ready-made meals so you do not have to spend energy cooking every day;
• Ask family or friends to help with shopping and cooking;
• Choose times to eat when you feel better.

Sometimes, eating more often in smaller portions is easier. If a large plate of food puts you off eating, several small meals throughout the day may be easier to manage.

How should cancer nutrition be adapted to the affected organ?

Nutrition during cancer depends on your condition, the characteristics of the disease, the treatment, and how well you tolerate different foods. Therefore, nutritional recommendations for breast cancer are not necessarily the same as those for tumors affecting the digestive or urinary systems.

When managing nutrition for intestinal cancer, it is important to consider changes in bowel movements and tolerance of certain foods. Nutrition for rectal cancer should also be individualized: a universal list of permitted and forbidden foods is not suitable for everyone.

With stomach cancer, you may need to reconsider portion sizes and how you eat, especially if you feel full quickly or experience discomfort after meals. For pancreatic cancer, your doctor will consider how well you tolerate food and whether you are getting the nutrients you need.

Nutrition for liver cancer and kidney cancer requires particular attention to your overall condition and any related health problems. Do not independently restrict protein, fluids, or other components of your diet. The right approach depends on your specific medical situation.

With bladder cancer, it is also important to follow your treating doctor's individual recommendations, consider food tolerance, and take other health conditions into account. The diagnosis alone does not mean that everyone must eliminate the same foods.

In all these cases, the main goal is to provide adequate nutrition and prevent dietary restrictions from causing energy deficiencies or weight loss. It is best to discuss specific dietary changes with your oncologist or a specialist in clinical nutrition.

How does nutrition affect your body during cancer treatment?

Cancer nutrition often comes down to a simple goal: giving your body enough energy and nutrients. Depending on your situation, you may need foods that provide protein, calories, vitamins, minerals, and sufficient fluids.

Protein is particularly important for maintaining body tissues. Sources include animal-based and plant-based foods. The choice depends on your individual tolerance, health, and your doctor's recommendations.

If eating ordinary meals is difficult, doctors sometimes recommend making food easier to manage: choosing foods you can tolerate more comfortably, preparing small portions in advance, and asking loved ones for help.

In some situations, cancer nutrition differs from the usual idea of “the healthiest food.” During treatment, you may need more protein and energy than someone who is not ill.

You may sometimes come across the term “cellular nutrition for cancer.” It can refer to different approaches involving nutrient intake and support for metabolic processes. However, the term itself does not describe a proven cancer treatment. Neither a special diet nor individual foods should be considered a substitute for anticancer therapy. If cellular nutrition involves supplements or specialized programs, discuss their ingredients and safety with your oncologist.

Do not independently switch to strict dietary restrictions, fasting, or so-called cleansing programs. During treatment, your body often needs a steady supply of nutrients. Before using any herb or supplement or changing your diet, tell your oncologist. Do not change prescribed treatment or medications on your own.

What I recommend … for cancer and regaining strength

I, Dr. Boris Wydoff, have spent more than fifty years studying how nutrition, movement, and lifestyle affect people's health. When it comes to cancer, I view nutrition as a way to support the body's strength and care for yourself during a difficult period.

My observations suggest that people undergoing demanding treatment often benefit not from searching for one “miracle food,” but from returning to simple daily habits: familiar foods, a routine, movement within their abilities, and a calm approach to their condition.

Bring more fresh, natural foods back to your plate. In my books, I write that vegetables and greens should play an important role in a natural diet. I associate “living” foods with a simpler, more natural way of eating. In my experience, a calm and straightforward approach to food can help people maintain a sense of stability during recovery.

You can gradually add vegetables, depending on how well you tolerate them. If you have bowel problems, pain, diarrhea, or other symptoms, discuss the right approach with a specialist.

Reduce foods that make your diet unnecessarily heavy. I recommend paying attention to excess sugar, white flour, and highly processed foods. In my books, I explain it this way: the body needs energy for recovery, not an additional burden from heavy foods. This is my perspective, based on my observations of people's eating habits.

At the same time, cancer treatment is not the time to turn nutrition into a rigid system of prohibitions. If you struggle to get enough calories and protein, your doctor may recommend a more energy-dense diet.

Use vegetable juices as an addition to your diet. I have written about freshly squeezed vegetable juices as part of my approach. I associate them with the idea of offering the body another way to obtain nutrients in an easily consumed form. My approach includes 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 when you have specific health conditions, take medications, or are undergoing treatment, discuss this with your oncologist.

Keep moving and stay warm in everyday life. I believe that walks, moderate activity, and keeping warm can help support a person's overall well-being. In my books, I associate movement with maintaining vitality and feeling well.

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

I have also written about food combining as my approach to pairing foods. Doctors do not consider separating foods an essential requirement of nutrition for cancer, but I see it as part of my perspective on making eating feel lighter. Discuss all dietary changes during treatment with your treating doctor.

Small practical steps to help maintain your strength

During treatment, it is helpful not to try to change everything at once. Gradually introducing habits is often more sustainable. You can start with simple steps:

• Drink enough fluids unless your doctor has prescribed a restriction;
• Plan your shopping in advance;
• Include a source of protein in meals where appropriate;
• Choose foods that are easier for you to tolerate;
• Keep track of changes in your appetite and well-being so you can tell your doctor.

If you feel worse after eating, it can help to note which foods cause discomfort. These records can help your specialist better understand your situation.

What to avoid during chemotherapy without your doctor's approval

During chemotherapy, discuss all supplements and major dietary changes with your oncologist. Some common foods and substances can affect treatment. Do not use St. John's wort or grapefruit without your doctor's approval, as they may change the levels of certain anticancer medications in your body. Do not take high doses of antioxidants on your own during chemotherapy or radiation therapy. You should also avoid herbal concentrates and extracts unless a specialist has approved them.

Ordinary fruits and vegetables are not forbidden foods. It is important to follow food safety practices, especially if treatment weakens your immune system. If your immunity is reduced, your doctor can explain food preparation guidelines and which foods you may need to avoid temporarily because of the risk of infection.

When to see a doctor

Seek medical help urgently

During chemotherapy, a temperature of 38 °C or higher or chills require you to contact your oncologist immediately. Do not try to lower a fever on your own before receiving medical advice. Urgent medical assessment is also needed if you experience shortness of breath, chest pain, leg swelling, vomiting lasting more than a day, or an inability to drink. Do not delay seeking help if you notice blood in your stool or vomit, black stools, fainting, or a rapid heartbeat.

Discuss your condition with your doctor at a scheduled appointment

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

• How much weight you have managed to maintain or have lost;
• Which foods you can no longer tolerate well;
• Whether you have nausea, vomiting, or changes in bowel movements;
• How much fluid you are able to drink;
• Whether you have developed difficulty swallowing.

Your doctor can help identify the cause of these changes and find appropriate support. It is especially important to report any new symptoms during treatment. You can read more about my approach to this topic on the “Cancer” page.

Boris Wydoff — naturopath and author, Ph.D. in nutrition. For over fifty years I have helped people restore health through nutrition, cleansing and the power of the mind — in Europe, America and Asia. About the author →

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