Diet and Lifestyle Guidelines

While research shows that a healthy diet may help prevent or halt the development of certain cancers, there is no one food or nutrient that has been proven to cure cancer or keep it from coming back.

Many studies have been done about nutritional strategies to prevent cancer. Much less is known about the best nutrition for people with cancer. Until more research is done, follow guidelines that can help prevent cancer and may also protect against its return.

Make plant foods the base of your diet. Research shows that eating plant foods can help fight cancer, because fruits and vegetables contain disease-preventing compounds called phytochemicals. These substances provide more health benefits than vitamins and minerals alone. They slow the absorption and disable or stop the binding of cancer-causing substances (carcinogens) within cells. They also may slow the growth of cancer cells.

The phytochemical content of different fruits and vegetables varies by color. Each has a unique function. Fruits and vegetables with cancer-fighting qualities include broccoli, cauliflower, cabbage, and Brussels sprouts (called cruciferous vegetables), citrus fruits and berries, onions and garlic, and brightly colored vegetables like carrots, squash, tomatoes, spinach, peppers, and beets.

Eat at least five or more servings of fruits and vegetables each day. Include several servings of whole grain breads, cereals, or beans. Limit the amount of high-fat foods, especially high-fat meats. Round out your diet with four to six ounces of protein a day from lean sources such as lean beef, pork, poultry, fish, beans, and lower-fat dairy products. Keep meats from charring when you grill them.

Maintain a healthy weight. People with cancer may gain or lose body weight during treatment and recovery. If you are losing weight and can’t meet your nutritional needs through regular food during treatment, you may want to try a liquid nutritional supplement. If you are gaining weight, follow a healthy eating plan that meets, but does not exceed, your caloric needs. If you are overweight, you should only try to lose weight after your treatment is complete.

Exercise regularly. Researchers have not yet been able to determine whether physical activity can prevent cancer from coming back or slow its growth. But studies have shown that regular activity can reduce anxiety and depression, improve mood and self-esteem and reduce symptoms of fatigue, nausea, pain, and diarrhea. Try to get 30 to 60 minutes or more of activity on most days of the week.

Limit alcohol and tobacco. The connection between tobacco and cancer is clear. Tobacco is the main cause of lung cancer, and plays a role in other types of cancer as well. If you use tobacco, talk to your doctor about ways to quit.

Alcohol may increase the risk of several cancers. Some evidence indicates alcohol may have health benefits. The substances found in red wine that may decrease the risk of certain cancers can also be obtained by eating fruits and vegetables. Cancer survivors should limit alcohol to no more than one to two drinks per day. If you are receiving cancer treatment, talk to your doctor before drinking any amount of alcohol.

Handle food safely. Food safety is important if your immune system is weakened. Wash your hands before eating, wash fruits and vegetables well and use special care when handling meats. Wash all utensils and countertops that come in contact with raw meat, and cook meat, poultry, and seafood well. Drink only pasteurized milk and juices. Store foods at low temperatures (below 40º F) to minimize bacterial growth. Thaw food in the refrigerator, not on the kitchen counter. In restaurants, avoid salad bars, sushi, and raw or undercooked meat, shellfish, poultry, and eggs.

Nutritional Therapies

Many people who are diagnosed with cancer hear about a wide variety of nutritional therapies that claim to cure cancer. Unfortunately, very few controlled clinical trials have been performed to test the impact of these nutritional methods. In the studies that have been done, the findings often don’t agree, making it difficult to make informed decisions. Discuss the use of these therapies with your health care team to assure they can be used safely with your treatment plan. Some of the most widely known nutritional therapies include:

• Supplements
  Because of the apparent anti-cancer effects of fruits and vegetables, which are rich in vitamins and minerals, some people believe that taking high doses of vitamin, mineral, or herbal supplements will destroy cancer cells. However, there is no evidence that any nutritional supplements, even in high doses, can provide the same benefits of a diet high in vegetables and fruits. Some vitamins and herbal compounds are toxic at high levels. Supplements, especially those that have not been well-tested, should only be used in moderate doses if at all. A multivitamin/mineral supplement that doesn’t exceed the recommended Daily Value (DV) may be helpful if you can’t eat enough to obtain these nutrients.
  
  Controversy surrounds the use of antioxidant supplements during treatment for cancer. More research needs to be conducted to establish if these supplements may be used safely during treatment.
  
• Phytochemical Supplements
  Scientists have identified hundreds of phytochemicals in foods. They believe there are thousands more. Each seems to have a unique role in protecting the body against cancer. However, it is unlikely that taking a supplement is as effective as eating phytochemical-containing foods, since it is believed that the various phytochemicals and vitamins found in foods act together to reduce cancer risk.
  
• Soy
  Soy contains high levels of phytochemicals (genistein and diadzein), which seem to show anti-cancer activity in laboratory studies. Soy foods may have good effects for some, and bad effects for others. Studies on soy and breast cancer have produced conflicting results. Some show that genistein reduces the growth of cancer cells, and others show it increases growth. People with breast cancer should only use moderate amounts of soy foods. They should not supplement their diets with more concentrated sources of soy like pills, powders, or supplements.
  
• Vegetarian Diets
  Vegetarian diets can have a variety of healthy qualities, since they tend to be low in saturated fats and high in fiber, vitamins, and phytochemicals. At this time, however, there is no evidence that a vegetarian diet can prevent cancer from coming back. If you choose to follow a strict vegetarian diet, you may need to take a vitamin B12 supplement.
  
• Macrobiotic Diets
  Macrobiotic diets are based on whole grains and cereals, specific vegetables, seaweed, beans, fruits, nuts, seeds, miso soup, and teas. There is no clear scientific evidence these cure or prevent cancer. Macrobiotic diets are very restrictive. Cancer survivors choosing these diets should take special care to make sure they’re getting enough calories and nutrients.

Evaluating Nutrition Information

New claims about nutritional treatments and cures for cancer are everywhere. Learn to evaluate this type of information. Keep these points in mind:

• “Natural” doesn’t necessarily mean safe. Even natural substances can be toxic at high levels. They may also interfere with medications or other treatments.
• Unlike prescription and over-the-counter drugs, dietary supplements are not regulated. Supplements can be sold without government approval or safety testing.
• Nutrition information should come from a trusted medical or health-related association. It should be reviewed by qualified health professionals. Beware of information that comes only from those who are selling a product.
• Do the people promoting an alternative treatment claim the medical community is trying to keep their cure from the public? That can signal a scam. No one committed to finding better ways to treat a disease would knowingly keep people from using an effective treatment. Also watch out for anyone who claims to have a “secret formula.” Scientists who believe they have developed an effective treatment publish their results in medical journals where they can be read by other researchers.
• Beware of results claiming to offer a “quick-fix” or using words like “miracle” or “breakthrough.” Science progresses in small steps, not in dramatic discoveries that occur overnight.
• Always remember, if it sounds too good to be true, it probably is!

If you have specific questions about nutrition and cancer, talk to your doctor, nurse, or a registered dietitian.