Virtual Medical Centre

Nutrition in Cancer Patients

• Introduction to nutrition in cancer patients
• Nutritional concerns for cancer patients
• Dietary supplementation

Introduction to nutrition in cancer patients

Cancer treatment often involves one or a combination of surgery, radiation therapy, chemotherapy, hormone therapy, and biologic immunotherapy. These conventional methods of treatment are aimed at killing cancer cells, but ultimately kill some healthy cells as well. Cancer patients therefore have the double burden of fighting cancerous cells and finding ways of replacing damaged cells.  

Nutritional concerns for cancer patients

The nutritional needs of a cancer patient depend on several factors, including the stage of the disease (i.e. treatment, recovery and living after recovery), the symptoms experienced, the type and frequency of the cancer treatment being used and the side effects associated with that treatment, and the effect of the specific cancer on food and nutrient ingestion, tolerance, and utilisation. For many cancer patients, managing nutritional needs while living with advanced cancer becomes a particular challenge that needs to be overcome.

The onset of cancer is reported to cause profound metabolic and physiological changes which tend to increase the nutritional needs for protein, carbohydrate, fat, vitamins and minerals. Therefore, nutritional requirements are high during cancer treatment, and may lead to malnutrition. Malnutrition can be prevented simply by eating enough foods rich in nutrients and antioxidants. An adequate nutrient supply will assist the body in rebuilding damaged cells, and antioxidants may directly fight the cancer.

All methods of cancer treatment can influence nutritional needs, alter regular eating habits, and adversely affect how the body digests, absorbs, and uses food. Common side effects of cancer treatment that can lead to inadequate nutrient intake and subsequent malnutrition include:

• Loss of appetite (anorexia)
• Loss of lean mass
• Early satiety
• Changes in taste and smell
• Disturbances of the gastrointestinal tract
• Nausea and vomiting
• Diarrhoea
• Lactose intolerance
• Constipation
• Sore mouth or throat

These side effects therefore constitute a major nutritional and health risk for cancer patients.

The nutritional needs of people with cancer are different from the needs of the general population. Often, recommendations for healthy living focus on eating lots of fruits, vegetables, and whole grain breads and cereals; including a moderate amount of meat and dairy products; and cutting back on fat, sugar, alcohol, and salt. For cancer patients, the emphasis is on maintaining adequate energy balance. This presupposes the consumption of energy-dense foods, mainly to counteract the weight loss side effect that often accompanies cancer treatment.

Cancer patients often suffer from a substantial loss in weight and energy as a result of changes in appetite and metabolism. It is a known fact that appetite in cancer patients is adversely affected as a direct consequence of the disease and/or its treatments. Cancer patients are therefore vulnerable to malnutrition and may be predisposed to a poor health and quality of life. Substantial weight loss and poor nutritional status have been reported in more than half of cancer patients at the time of diagnosis, although the prevalence of malnutrition and weight loss varies widely across cancer types. 

The main nutritional recommendations for cancer patients are designed to:

• Help build up strength;
• Help withstand the effects of cancer and its treatment;
• Prevent or reverse nutrient deficiencies;
• Preserve lean body mass;
• Minimise nutrition-related side effects (such as decreased appetite, nausea, taste changes or bowel changes); and
• Maximise quality of life.

During cancer treatment, more calories than normal may be needed to help maintain energy levels. High-energy diets that also contain a substantial amount of protein (e.g. milk, cream, cheese, and cooked eggs) may help replenish energy and protein losses associated with cancer treatment. The best choices to meet protein needs are foods that are also low in saturated fat (e.g. fish, lean meat and poultry, eggs, nonfat and low-fat dairy products, nuts, seeds, and legumes).

Snack foods and other foods high in fat may therefore be more appropriate during cancer treatment. Additionally, consuming more sauces and gravies, or changing your cooking methods to include more butter, margarine, or oil, are commonly suggested to cancer patients.

Not all cancer patients lose weight. Instead, some gain weight (i.e. become obese). This is just as detrimental, since being overweight can complicate cancer treatment. While consuming a diet that is low in fat has been shown to be protective against heart disease, it is uncertain whether there is any benefit for preventing cancer recurrence. During cancer treatment, adding moderate amounts of fats and fat-containing foods can help improve calorie intake. However, after treatment, cancer patients should eat a diet low in high-fat foods and animal fats for optimal heart health.

Emerging evidence from some studies suggests that omega-3 fatty acids may have specific benefits for cancer patients, such as reducing cachexia, improving quality of life, and perhaps enhancing the effects of some forms of treatment. However, these findings are not conclusive, and more research is needed. Foods that are rich in omega-3 fatty acids (e.g. fish, walnuts) are associated with a lower risk for cardiovascular diseases and a lower overall mortality rate, and are therefore recommended for cancer patients.

Anaemia is common during and after cancer treatment, and may be attributed to blood loss, chemotherapy, and/or radiation therapy, or from the cancer itself. A balanced diet will help produce new blood cells. Iron supplements should be taken only after consulting your health care provider since extra iron may cause digestive system side effects.

Your dietitian can help you manage any nutrition-related issues arising from the cancer or cancer treatments. Examples of useful strategies include:

• For patients experiencing a reduced appetite: Consuming smaller, more frequent meals without liquids can help to increase food intake.
• For patients who cannot meet their nutritional needs through foods alone: Fortified and commercially-prepared or homemade nutrient-dense beverages or foods may improve the intake of energy and nutrients.
• For patients who are unable to meet their nutritional needs through these measures: Other means of short-term nutritional support may be needed, such as enteral nutrition via tube feeding, or intravenous parenteral nutrition.

Dietary supplementation

The use of dietary supplements during cancer treatment, such as vitamins, minerals, and herbal preparations, remains controversial. For example, it may be counterproductive for patients to take folate supplements or to eat fortified food products that contain high levels of folate while receiving methotrexate, a chemotherapy drug that acts by interfering with folate metabolism.

Currently, available scientific evidence for the use of dietary supplements is inconclusive. Some cancer experts advise against taking higher doses of supplements with antioxidant activity during treatment because antioxidants could prevent the cellular oxidative damage to cancer cells that are required for treatments such as radiotherapy and chemotherapy to be effective. In contrast, others have noted that the possible harm from antioxidants is only hypothetical, and that there may be a net benefit to help protect normal cells from the collateral damage associated with these therapies.

For more information, see Vitamins, Supplements and Cancer.