- Introduction to nutrition and cancer
- Nutritional concerns for people with cancer
- Dietary supplementation
- Management of common side effects during cancer treatment
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.
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
- Lactose intolerance
- 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.
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.
A number of cancer treatment side effects can be dangerous if allowed to go untreated. Some of these side effects are outlined as follows:
Loss of appetite (anorexia) is commonly experienced after cancer treatment. The exact cause of appetite loss is unknown, but it may be due to the the cancer itself, side effects of cancer treatment (e.g. nausea, fatigue), or to feeling upset.
Try the following strategies to manage appetite loss:
- Try not to miss meals.
- Small meals eaten more often may be easier to manage. Try to eat every 2–3 hours during the day. Serve small food portions.
- There may be times of the day when you feel more like eating. Take advantage of this by eating well at these times.
- Drink after and between meals. Avoid drinking fluids half an hour before meals and during mealtimes – they tend to fill you up, so that you eat less.
- Try liquid or powdered meal replacements, a useful option if you find it very difficult to eat.
- Treat yourself to your favourite foods.
- If you do not feel like preparing a meal, have frozen meals and a range of ready prepared foods and snacks on hand. Nourishing snacks include cheese and crackers, muffins, ice cream, peanut butter, fruit and pudding.
- Choosing a variety of different foods may help increase your appetite. For example, you may choose whole fresh fruit, mixing fruit into a milkshake, or canned fruit.
- Regular exercise may help improve your appetite.
- Enjoy meals as a social occasion – eat with family and friends whenever possible.
Many cancer patients lose weight during treatment. This may be due to the effects of the cancer itself, or to inadequate food intake due to the side effects of cancer treatment (e.g. nausea, sore mouth, taste changes). If you are underweight or losing weight, you need to include more protein and energy (calories or kilojoules) in your diet.
To achieve this, try:
- Including high protein foods, such as meat, chicken, fish, eggs, legumes (e.g. baked beans, lentils), tofu, dairy products and nuts.
- Including high fat foods, such as oil, margarine, cream, avocado, salad dressing, mayonnaise and cream.
- Frequent snacking.
Weight gain may arise from fluid gain. Certain anti-cancer drugs can cause your body to hold on to excess fluid. This condition is called oedema. Patients with oedema may have to limit their salt intake, as salt causes your body to hold extra water. A diuretic may be prescribed to help your body get rid of excess fluid.
Weight gain may also be the result of increased appetite and eating extra food and energy. For patients with breast, prostate and ovarian cancer who are gaining weight, the following strategies may help prevent further weight gain and achieve weight maintenance during treatment:
- Consume moderate portion sizes of mostly vegetables, fruits, breads, cereals and other low fat foods as the basis of the diet.
- Choose lean meats (lean beef or pork trimmed of fat, chicken without skin) and low-fat dairy products (e.g. skim milk).
- Choose low-fat and low-calorie cooking methods (broiling, steaming).
- Consume less oil, butter, mayonnaise, sugar-containing beverages (e.g. fruit juice, cordial, soft drink), sweets, and other ’empty calorie’ foods such as sugar.
- Enjoy regular physical activity.
It may be helpful to discuss strategies specific for your needs with your dietitian.
Radiation therapy, chemotherapy, or infection can result in mouth sores, tender gums, and a sore throat or oesophagus. Patients who have a sore mouth or throat are first of all advised to consult their doctor for a proper diagnosis of the problem. Your doctor can recommend medications to relieve mouth and throat discomfort (e.g. anaesthetic mouthwash) and, if needed, treat mouth infections.
Dietary strategies to relieve a sore mouth and throat and assist with maintaining an adequate intake include:
- Avoid foods that may cause irritation (e.g. oranges, grapefruits, lemons, or other citrus fruit or juice; tomato sauces or juice; spicy or salty foods; raw vegetables; toast, crackers, or other rough, coarse or dry foods). Chopped, blended, diced or pureed foods may be easier to eat, as they require little or no chewing and are easy to swallow.
- Cook foods until they are soft and tender.
- Cut foods into small pieces.
- Use a blender or food processor to puree your food.
- Mix food with butter, margarine, thin gravy or sauce to make it easier to swallow.
- Use a straw to drink liquids.
- Use a smaller-than-usual spoon, such as a baby spoon.
- Try foods cold or at room temperature. Hot foods can irritate a tender mouth and throat.
- Try drinking warm bouillon or salty broth; it can soothe throat pain.
- If swallowing is difficult , tilting your head back or moving it forward may help.
- Rinse your mouth often with water to remove food and bacteria, and to promote healing.
- Ask your doctor about anaesthetic lozenges and sprays that can numb your mouth and throat long enough for you to eat meals.
Nausea, with or without vomiting, is a common side effect of cancer treatment. Nausea can stop you from eating enough food and maintaining your nutritional intake and weight.
Dietary strategies to manage nausea include:
- Discuss anti-nausea (antiemetic) medications with your doctor.
- Avoid eating 1–2 hours before your treatment if this makes nausea worse. Try to ‘catch up’ with your meal after treatment.
- Avoid foods that:
- Are fatty, greasy or fried
- Are spicy or hot
- Have strong odours
- Eat small amounts, often and slowly.
- Eat before you get hungry, because hunger can make feelings of nausea stronger.
- Avoid eating in a room that is stuffy, too warm, or has cooking odours that might disagree with you.
- Sip cold clear fluids (e.g. cordial, flat ginger ale, lemonade, diluted fruit juices, icy pole, jelly). This is particularly important for preventing dehydration if you are vomiting.
- Have foods and drinks at room temperature or cooler; hot foods may add to nausea.
- Rest after meals, because activity may slow digestion. Rest while sitting up for about an hour after meals.
- Choose stomach-friendly foods (e.g. toast, crackers, yoghurt, angel food cake, cream of wheat, rice or oatmeal, boiled potatoes, noodles, baked or broiled skinned chicken, canned peaches or other soft, bland fruits and vegetables, and carbonated drinks).
- If vomiting continues after a day or two, contact your doctor or treatment centre.
Article kindly reviewed by:
The DAA WA Oncology Interest Group
Food4Health (Helen Baker Dietitian-APD)
For more information on nutrition, including information on types and composition of food, nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.
For more information on breast cancer, types of breast cancer and its investigations and treatments, as well as some useful videos, see Breast Cancer.
For more information on gastric cancer, including different types of gastric cancer, see Gastric Cancer.
|For more information on kidney cancer, including types and treatment, see Kidney Cancer|
For more information on prostate cancer, including diagnoses, types of treatments, and some useful tools, videos and animations, see Prostate Cancer.
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