Plenty of research has demonstrated the benefits of a healthy diet for cancer prevention. But good nutrition is equally important for people with cancer.
Cancer and cancer treatments can reduce your appetite and affect the body's ability to tolerate certain foods and use nutrients. Eating well while undergoing cancer treatment can help you feel more energetic, maintain your weight and muscle mass, prevent infections - and heal and recover more quickly.
Research also suggests that people who are well nourished are better able to tolerate some of the side effects of treatment. They may be able to handle higher doses of certain drugs and have a higher rate of therapy completion. What's more, some cancer treatments are more effective in people who consume adequate calories and protein.
It is estimated that more than half of people diagnosed with cancer receive chemotherapy, a treatment that can make eating well easier said than done. Side effects such as reduced appetite, fatigue, nausea and vomiting, mouth sores and taste changes can affect the ability - and desire - to eat.
(Chemotherapy refers to the use of drugs to treat cancer. It works by slowing or stopping the growth and multiplication of cancer cells. However, it also harms healthy cells, which causes side effects.)
Eating plenty of fruits and vegetables might improve your response to chemotherapy. Last month, a new study from the University of California, Riverside found that apigenin - a naturally occurring compound in fruits and vegetables - helped increase the sensitivity of cancer cells to chemotherapy drugs.
Apigenin is found in fruit (including apples, cherries, grapes), vegetables (including parsley, artichoke, basil, celery), nuts and tea. Lab studies suggest it can inhibit the growth of breast, colon, prostate, skin, thyroid and leukemia cancer cells.
Certain vitamin supplements, on the other hand, may blunt the effectiveness of cancer drugs. A recent study from the Memorial Sloan-Kettering Cancer Center in New York revealed that 30 to 70 per cent fewer human cancer cells were killed by chemotherapy drugs when the cells were pretreated with vitamin C in lab dishes. It is thought that by protecting the mitochondria in cancer cells from harm, vitamin C may prevent chemotherapy drugs from working to their full potential. (When mitochondria, the parts of cells that generate energy, are damaged by drugs, they send signals to the rest of the cell to die.)
There has been much debate on the use of antioxidant supplements including vitamins C and E and beta carotene during chemotherapy and radiation. The concern is that antioxidants may decrease the anti-cancer activity of these drugs. (Chemotherapy and radiation work by generating free radicals to kill cancer cells; antioxidants work by neutralizing these free radicals.)
On the other hand, some studies have suggested that by protecting healthy cells from free radical damage, antioxidants reduce the side effects of chemotherapy without interfering with the action of the drugs.
After more than two decades of research, there is not enough evidence to support taking antioxidant supplements during cancer treatment. A review of 19 randomized controlled trials published in May, 2008, concluded there was potential harm from using these supplements during radiation therapy, and they should therefore be avoided. The review found limited evidence to warrant taking antioxidants during chemotherapy.
Whether you or a loved one are preparing for surgery or going through chemo or radiation, the following nutrition tips can help defend against infections, fight fatigue and maintain your weight.
During cancer treatment, adequate protein can help preserve muscle mass, body tissues and weight. After treatment, extra protein is needed to heal tissues and prevent infection.
Good sources of protein include lean meat, poultry, fish, egg whites, dairy products and legumes. If you can't get enough protein from your diet, use commercial meal replacements, in the form of liquid supplements (such as Ensure and Boost) and instant-breakfast products. If you are sensitive to lactose, check labels to choose a lactose-free product.
Consider making your own protein shake with whey protein powder, milk and fruit. Whey protein powder can be added to any food or beverage.
EAT LESS, MORE OFTEN
If nausea and poor appetite prevent you from eating full-sized meals, eat small meals or snacks every one to two hours to prevent feeling too full. If you don't feel like eating solid foods, drink juice, soup, smoothies and protein shakes during the day to provide calories and nutrients.
Eat your largest meal when you feel the hungriest, often in the morning. Avoid drinking large amounts of fluids with meals to prevent feeling too full. If possible, take a walk before meals to stimulate your appetite.
To help manage nausea, sip sports drinks, clear juices, flat carbonated beverages or herbal tea between meals.
Eating small portions of dry, starchy foods such as bread, crackers and cereal can also help combat nausea. Peppermint candy or peppermint gum may also settle your stomach.
AVOID IRRITATING FOODS
Mouth sores, tender gums and sore throat can result from cancer therapy and make chewing and swallowing difficult. Foods that can irritate your mouth include citrus fruit, tomato sauce, spicy foods, salty foods, raw vegetables and dry foods such as toast and crackers.
Soft foods (e.g. milkshakes, yogurt, cottage cheese, pudding, applesauce, scrambled eggs, bananas) are usually well tolerated.
PRACTISE FOOD SAFETY
When undergoing cancer treatment, your immune system can be diminished, temporarily making you more susceptible to food poisoning. To minimize the risk of infection, cook meat, poultry, seafood and eggs thoroughly. Avoid unpasteurized dairy products and juice, cold smoked fish, raw tofu and unwashed produce.
CONSIDER A MULTIVITAMIN
If you find it hard to eat a balanced diet during cancer treatment, speak to your oncologist or dietitian about taking a multivitamin supplement. Avoid "mega" or "high potency" products that may contain large amounts of some nutrients. If you are undergoing radiation, speak to your doctor about the best time to take a multivitamin.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.