When you’re healthy, eating enough food to get the nutrients and calories you need is not usually a problem. Most nutrition guidelines stress eating lots of vegetables, fruits, and whole-grain products; limiting the amount of red meat you eat, especially meats that are processed or high in fat; cutting back on fat, sugar, alcohol, and salt; and staying at a healthy weight. But when you’re being treated for cancer, these things can be hard to do, especially if you have side effects or just don’t feel well.
Good nutrition is especially important if you have cancer because both the illness and its treatments can change the way you eat. They can also affect the way your body tolerates certain foods and uses nutrients.
During cancer treatment you might need to change your diet to help build up your strength and withstand the effects of the cancer and its treatment. This may mean eating things that aren’t normally recommended when you are in good health. For instance, you might need high-protein, high-calorie foods to keep up your weight, or thick, cool foods like ice cream or milk shakes because sores in your mouth and throat are making it hard to eat anything. The type of cancer, your treatment, and any side effects you have must be considered when trying to figure out the best ways to get the nutrition your body needs.
The nutrition needs of people with cancer vary from person to person. Your cancer care team can help you identify your nutrition goals and plan ways to help you meet them. Eating well while you’re being treated for cancer might help you:
- Feel better.
- Keep up your strength and energy.
- Maintain your weight and your body’s store of nutrients.
- Better tolerate treatment-related side effects.
- Lower your risk of infection.
- Heal and recover faster.
Eating well means eating a variety of foods to get the nutrients your body needs to fight cancer. These nutrients include proteins, fats, carbohydrates, water, vitamins, and minerals.
Proteins
We need protein for growth, to repair body tissue, and to keep our immune systems healthy. When your body doesn’t get enough protein, it might break down muscle for the fuel it needs. This makes it take longer to recover from illness and can lower resistance to infection. People with cancer often need more protein than usual. After surgery, chemotherapy, or radiation therapy, extra protein is usually needed to heal tissues and help fight infection.
Good sources of protein include fish, poultry, lean red meat, eggs, low-fat dairy products, nuts and nut butters, dried beans, peas and lentils, and soy foods.
Fats
Fats play an important role in nutrition. Fats and oils serve as a rich source of energy for the body. The body breaks down fats and uses them to store energy, insulate body tissues, and transport some types of vitamins through the blood.
You may have heard that some fats are better for you than others. When considering the effects of fats on your heart and cholesterol level, choose monounsaturated (olive, canola, and peanut oils) and polyunsaturated fats (these are found mainly in safflower, sunflower, corn, and flaxseed oils and seafood) more often than saturated fats or trans fats.
Saturated fats are mainly found in animal sources like meat and poultry, whole or reduced-fat milk, cheese, and butter. Some vegetable oils like coconut, palm kernel oil, and palm oil are saturated. Saturated fats can raise cholesterol and increase your risk for heart disease. Less than 10% of your calories should come from saturated fat.
Most trans fats in our diets come from snack foods and baked goods made with partially hydrogenated vegetable oil or vegetable shortening. These sources of trans fats have largely been removed from the food supply in the US. Trans fats are also found naturally in some animal products, like dairy products, in smaller quantities. Trans fats can raise bad cholesterol and lower good cholesterol. Avoid trans fats as much as you can.
Carbohydrates
Carbohydrates are the body’s major source of energy. Carbohydrates give the body the fuel it needs for physical activity and proper organ function. The best sources of carbohydrates – fruits, vegetables, and whole grains – also supply needed vitamins and minerals, fiber, and phytonutrients. (Phytonutrients are chemicals in plant-based foods that we don’t need to live, but that might promote health.)
Fiber is the part of plant foods that the body can’t digest. There are 2 types of fiber. Insoluble fiber helps to move food waste out of the body quickly, and soluble fiber binds with water in the stool to help keep stool soft.
Other sources of carbohydrates include bread, potatoes, rice, spaghetti, pasta, cereals, corn, peas, and beans. Sweets (desserts, candy, and drinks with sugar) can supply carbohydrates, but provide very little in the way of vitamins, minerals, or phytonutrients.
Water
Water and liquids or fluids are vital to health. All body cells need water to function. If you don’t take in enough fluids or if you lose fluids through vomiting or diarrhea, you can become dehydrated (your body doesn’t have as much fluid as it should). If this happens, the fluids and minerals that help keep your body working can become dangerously out of balance. You get water from the foods you eat, but a person should also drink about four 8-ounce glasses of liquid each day to be sure that all the body cells get the fluid they need. You may need extra fluids if you’re vomiting, have diarrhea, or even if you’re just not eating much. Keep in mind that all liquids (soups, milk, even ice cream and gelatin) count toward your fluid goals.
Vitamins and minerals
Your body needs vitamins and minerals to help it function properly and use the energy (calories) in food. Most are found naturally in foods, but they are also sold as pill and liquid supplements.
If you eat a balanced diet with enough calories and protein you will usually get plenty of vitamins and minerals. But it can be hard to eat a balanced diet when you’re being treated for cancer, especially if you have treatment side effects. If you do have side effects, your doctor or dietitian may suggest a daily multivitamin and mineral supplement. If your food intake has been limited for several weeks or months because of the effects of treatment, be sure to tell your doctor. You might need to be checked for vitamin or mineral deficiencies.
If you’re thinking of taking a supplement, be sure to discuss this with your doctor first. Some people with cancer take large amounts of vitamins, minerals, and other dietary supplements to try to boost their immune system or even destroy cancer cells. But some of these substances can be harmful, especially when taken in large doses. In fact, large doses of some vitamins and minerals may make chemotherapy and radiation therapy less effective.
If your doctor says it’s OK for you to take a vitamin during treatment, it may be best to choose a supplement with no more than 100% of the Daily Value (DV) of vitamins and minerals and one without iron (unless your doctor thinks you need iron).
Antioxidants
Antioxidants include vitamins A, C, and E; selenium and zinc; and some enzymes that absorb and attach to free radicals (destructive molecules) , preventing them from attacking normal cells.
If you want to take in more antioxidants, health experts recommend eating a variety of fruits and vegetables, which are good sources of antioxidants. Taking large doses of antioxidant supplements or vitamin-enhanced foods or liquids is usually not recommended while getting chemo or radiation therapy. Talk with your doctor to find out the best time to take antioxidant supplements.
Phytonutrients
Phytonutrients or phytochemicals are plant compounds like carotenoids, lycopene, resveratrol, and phytosterols that are thought to have health-protecting qualities. They’re found in plants such as fruits and vegetables, or things made from plants, like tofu or tea. Phytochemicals are best taken in by eating the foods that contain them rather than taking supplements or pills.
Herbs
Herbs have been used to treat disease for hundreds of years, with mixed results. Today, herbs are found in many products, like pills, liquid extracts, teas, and ointments. Many of these products are harmless and safe to use, but others can cause harmful side effects. Some may even interfere with cancer treatments and recovery from surgery. If you’re interested in using products containing herbs, talk about it with your cancer doctor, nurse, or pharmacist first.
Dietary supplement safety considerations
Many people believe that a pill or supplement they find in stores, is safe and it works. The Food and Drug Administration (FDA) has rules to help ensure that supplements contain what their labels claim they do, but the supplement’s safety and its effects on the body are not addressed by any FDA rules. The FDA does not make manufacturers of these products print possible side effects on their labels. And the FDA can’t pull a dietary supplement or herbal product from the market unless they have proof that the product is unsafe.
It’s also been shown that many herbal products aren’t what the label says they are. Some products don’t contain any of the herb they’re supposed to. Some also contain potentially harmful drugs, additives, or contaminants that aren’t listed on the label. This means there’s no sure way to know if a supplement is safe or how it will affect you.
Tell your cancer care team about any over-the-counter products or supplements you‘re using or are thinking about using. Take the bottle(s) to your doctor to talk about the dose and be sure that the ingredients do not interfere with your health or cancer treatments. Some other safety tips:
- Ask your cancer care team for reliable information on dietary supplements.
- Check the product labels for both the quantity and concentration of active ingredients in each product.
- Stop taking the product and call your cancer care team right away if you have side effects, like wheezing, itching, numbness, or tingling in your limbs.