Commonly asked questions

Eating well can help you:

• Keep your strength and energy
• Maintain your weight and muscle mass
• Cope with side effects from your treatment
• Lower your risk of infection
• Lower your risk of a hospital stay
• Heal and get better faster

Speak to a dietitian if you:

• Have lost weight without trying
• Have problems eating
• Have questions about nutrition

If you are a patient at the Odette Cancer Centre, nutrition services are a part of your care. You do not need a referral from your doctor to speak with a dietitian. To book an appointment with a dietitian, visit or call Odette Patient and Family Support.

If you are not a patient at Odette, ask a member of your health care team about what nutrition services are available to you.

During cancer treatment it is important that your diet gives you enough calories, protein, and fluid.

• Calories give you energy and help you gain or maintain weight. Try to eat and drink enough calories to maintain your weight.
• Protein helps you build a healthy immune system, keep your muscle mass and strength, and fight infection. In general, people who get cancer treatment need more protein than usual. Try to include a protein food or fluid at each meal and snack. Read more about protein here.
• Fluid helps your body digest food, get rid of waste, flush out medications, keep a normal blood pressure and body temperature, and protect your organs and joints. Try to drink at least 9 cups of fluid each day to prevent dehydration, unless your doctor tells you not to.

The types of foods you eat to meet your calorie, protein, and fluid needs will depend on your symptoms and side effects.

If you have lost weight or have problems eating, please speak with a dietitian at your cancer centre.

If your weight is stable and you do not have problems eating, follow Canada's Food Guide with extra protein. Fill your plate with protein foods, whole grains, fruits, and vegetables. Drink fluids like water, milk, or soy milk. Choose plant protein foods often, like dried beans, peas, and lentils.

When it comes to nutrition and cancer, the best way to help your body fight cancer and heal is to:

• Eat enough calories to maintain your weight
• Eat enough protein to meet your needs
• Drink enough fluid to prevent dehydration

Evidence for “cancer-fighting foods” or foods with “anti-cancer properties” is mostly based on research to prevent cancer. We know that eating a diet filled with plant foods (like vegetables, fruits, whole grains, and legumes) helps lower cancer risk, but it is unclear if these foods slow cancer growth or prevent cancer from coming back.

If your weight is stable and you do not have problems eating, follow Canada's Food Guide with extra protein. This eating pattern makes it easy to meet your calorie, protein, and fluid needs, and packs in lots of plant foods for their potential cancer-fighting benefits.

If you have lost weight or have problems eating, foods like fruits and vegetables may not be the best choice. You may need to choose high-calorie and high-protein foods and fluids, or avoid certain foods to help with side effects. If that means not eating a balanced diet while you are on treatment, that is OK. Please speak with a dietitian for personalized advice.

If you have side effects from treatment, like diarrhea, nausea, taste changes, or painful swallowing, avoiding certain foods and fluids might help. Please speak with a dietitian.

Cancer treatments can make it harder for your immune system to fight infection. Always follow good food safety practices to lower your risk of foodborne illness. Wash your hands with warm soapy water before and after cooking and eating. Cook foods well. Remember to:

• Avoid undercooked or raw meat, poultry, seafood (like sushi), and eggs.
• Avoid unpasteurized dairy products and juices.
• Avoid home-canned foods, and foods from bulk bins, salad bars, delicatessens, buffets, potlucks, and sidewalk vendors.

For more information, see Health Canada’s tips on food safety for people with a weakened immune system.

The American Institute for Cancer Research and the World Cancer Research Fund recommends the following before and after a cancer diagnosis:

• Avoid or limit alcohol to one drink per day for women and two drinks per day for men.
• Limit red meat (like beef, pork, lamb, mutton, horse, and goat) to about three portions per week. One portion is 4–6 oz (120 - 165 g) of cooked meat.
• Avoid processed meat (like ham, salami, bacon, and hot dogs).

No, unless your doctor tells you to lose weight, we do not suggest you try to lose weight before or during cancer treatment or while in recovery.

Weight loss lowers your body’s ability to fight cancer and heal.

Before and during treatment, try to eat enough calories to maintain your weight and enough protein to meet your increased needs. If you have lost weight, please speak with a dietitian.

When you have recovered from treatment, a dietitian can help you work towards a healthy body weight.

For more information on the benefits of good nutrition during treatment, see "Why is nutrition important?" and "What should I eat during cancer treatment?"

If you have cancer, eating sugar does not make cancer cells grow faster.

All cells in your body, including cancer cells, need energy to grow. Their main source of energy is blood sugar, also known as glucose. Your body usually gets glucose by breaking down carbohydrate foods, which include sweets, grains, beans, dairy, fruits, and some vegetables.

Some people think they can starve cancer cells by avoiding carbohydrate foods. This is not true and is not recommended. If you avoid carbohydrate foods, your body will break down fat and muscle for energy instead, which can cause weight loss and malnutrition.

Carbohydrate foods with natural sugars, like whole grains, beans, fruit, starchy vegetables, and milk, are a good source of vitamins, minerals, fibre, and phytonutrients. If you feel well and have not lost weight, choose these carbohydrate foods and limit added sugars.

Added sugar is found in foods like desserts, sugary cereals, and sugary drinks. These foods have few nutrients but have lots of calories. If you have lost weight or have problems eating, your dietitian may tell you to choose high-calorie, high-protein foods and fluids often. This may mean eating some sugary foods like milkshakes and puddings, and that is OK.

For more information, see the American Institute for Cancer Research’s blog on The Sugar and Cancer Connection.

Yes, current research suggests it is safe to eat moderate amounts of whole soy foods before and after a cancer diagnosis. This is true for breast cancer survivors, as well.

Moderate amounts of soy is one to two standard servings daily. One standard serving is:

• 1/3 cup (65 g) tofu
• 1 cup (250 ml) soy milk
• ½ cup (125 ml) edamame
• ¼ cup (60 ml) soy nuts

Soy foods have compounds called isoflavones, which are similar to estrogen in the body. For this reason, some people worry that soy may put them more at risk for hormonally-sensitive cancers. Some of this confusion comes from animal studies, which have linked high doses of isoflavones with breast cancer in mice. We now know that mice and humans process soy differently. In fact, human studies suggest that eating whole soy foods may actually help protect against colorectal, prostate, and breast cancers, but more research is needed.

Soy supplements, which have much higher levels of isoflavones than soy foods, are not recommended.

Soy foods are a good source of protein. Read more about the importance of protein during cancer treatment here. 

To learn more about soy and cancer, check out the American Institute for Cancer Research’s food facts on soy.

Yes, it is safe to eat dairy products before and after a cancer diagnosis. Dairy products include milk, cheese, and yogurt. These foods are a good source of nutrients like protein, calcium, and vitamin D. Read more about the importance of protein during cancer treatment here. 

Research suggests eating dairy products lowers the risk of colorectal cancer, and may lower the risk of premenopausal breast cancer.

There is some evidence that eating dairy may increase the risk of prostate cancer, but more research is needed. The American Institute for Cancer Research and the World Cancer Research Fund do not recommend avoiding dairy to lower your risk.

If you are healthy or have cancer but have not lost weight, choose lower-fat dairy products.

If you have lost weight or have problems eating, choose higher fat dairy products like whole 3.25% milk and full-fat yogurt. These foods have more calories and can help you meet your nutrition needs.

What about growth hormones and antibiotics?

Some people worry that dairy products have growth hormones and antibiotics in them. In Canada, farmers are not allowed to use growth hormones in dairy cows. Sometimes cows are given antibiotics to treat an infection. The milk they make while on antibiotics is thrown out. All milk sold in Canada is tested to make sure it does not have any amount of antibiotics.

Yes, moderate amounts of lean red meat - such as lean beef, veal, and pork - can be part of a healthy diet. Red meat is a good source of protein, iron, zinc, and vitamin B12, but too much meat can increase your risk of colorectal cancer. If you do eat red meat, limit your intake to three servings each week. One serving is about 4–6 oz. (120–165 g) cooked weight.

For more information on other good protein sources, click here. 

Any amount of processed meat can increase your risk of colorectal cancer. Processed meat is meat preserved by curing, salting, smoking, or adding preservatives. This includes ham, bacon, pepperoni, deli meats, sausages, and hot dogs. Try to only eat processed meat at special occasions, if at all.

No, unless told otherwise by your doctor, your vitamin and mineral needs when you have cancer are the same as the needs of a healthy adult. A regular dose multivitamin-mineral supplement may help if you cannot eat a variety of foods. Your doctor or dietitian may recommend a multivitamin-mineral supplement.

Big doses of vitamins and minerals can be harmful and are usually not recommended. Talk to your doctor, dietitian, or pharmacist about any vitamin and mineral supplements you are taking.

Antioxidants

Supplements of antioxidants, like vitamin C, vitamin E, beta-carotene, and selenium, are not recommended during treatment.

Some cancer treatments work by making free radicals (abnormal oxygen molecules) to kill cancer cells. Antioxidants work by protecting both normal and cancer cells from free radicals. This means that taking antioxidant supplements may make your treatment less effective.

It is safe to eat antioxidants found in foods and regular dose multivitamin-mineral supplements during treatment. They have much smaller amounts of antioxidants in them.

Some people worry that pesticides used on non-organic fruits and vegetables will raise their cancer risk. Studies have shown evidence for and against this, and more research is needed.

What we do know is that a diet filled with plant foods – organic or not – is one of the best ways to lower your risk of cancer through diet. Organic food can be expensive. Choose non-organic food if it means you will eat more fruits and vegetables. Peeling and washing fruits and vegetables well can also lower your exposure to pesticides.

If you are healthy or have cancer but have not lost weight, follow Canada's Food Guide to help you get the recommended amount of plant foods each day.

For more information on the safety of organic and non-organic fruits and vegetables, visit the Safe Fruits and Veggies website.

No, there is no evidence that an alkaline diet prevents or fights cancer.

Supporters of an alkaline diet believe that eating alkaline foods helps control their blood’s pH (a measure of how acidic or alkaline something is). The goal of the alkaline diet is to prevent an acidic environment in your body that may promote cancer growth.

Your lungs and kidneys make sure your blood’s pH stays within a healthy, slightly alkaline range, no matter what you eat. Very acidic or alkaline substances are removed from your blood and come out in your urine. Your diet cannot change your blood’s pH but it can change the pH of your urine - this is just a sign your kidneys are doing their job.

For more information, check out the Canadian Cancer Society’s website – Is an alkaline diet better for you? –or the American Institute for Cancer Research’s blog post – Another Cancer and Diet Claim: The Alkaline Diet.

As of today, no major cancer organization recommends fasting during cancer treatment.

There is some evidence that fasting for a short period of time before and after certain cancer treatments may help them work better and lower your risk of side effects. More human studies are needed.

If you feel well, your weight is stable, and you would like to try fasting, speak to your health care team about how to do so safely.

We do know that weight loss during cancer treatment makes it harder for the body to fight cancer and heal. If you have lost weight or have problems eating, fasting can make things worse. Instead, focus on high-calorie and high-protein foods and fluids and speak to a dietitian at your cancer centre.

No major cancer organization recommends the ketogenic diet for cancer treatment. Some studies show possible benefits, but overall research is lacking.

A ketogenic diet is a very low-carbohydrate, moderate-protein, high-fat diet. It can change how your body burns food for energy. Usually cells get energy from blood sugar (glucose) by burning carbohydrates. If carbohydrates are limited, however, your body will burn ketones from fat. Healthy cells can adapt to this change, but it is believed that some cancer cells cannot. Some research in mice and a few small human studies on certain types of brain tumours suggest this may be true, but more research is needed.

Following a ketogenic can mean weighing all of your food and testing either your urine or blood for ketones, daily. It can be high in red and processed meats - both known to increase cancer risk - and low in healthy plant foods like fruits, vegetables, whole grains, and legumes. Trying a ketogenic diet on your own can lead to constipation, an upset stomach, malnutrition, and weight loss. If it is something you are interested in, speak to a dietitian with experience in the ketogenic diet.

Current research shows a diet with plenty of plant foods that meets your calorie, protein, and fluid needs is best for most cancer patients. See "What should I eat during cancer treatment?" for more information.

Cancer itself and some cancer treatments, like chemotherapy and radiation, can cause the bone marrow to make fewer blood cells than normal. This can lead to low counts of white blood cells, red blood cells, or platelets. These counts usually go back to normal before the next round of treatment or after treatment is completed.

There are no special foods or diet changes proven to increase blood cell counts. Your body does need certain nutrients to make new blood cells, like protein, folate, vitamin B12, and iron. Not getting enough of these nutrients can make your blood cell counts worse.

Try to include a protein food at each meal and snack. Read more about the importance of protein here.

Click here to learn more about foods high in folate, vitamin B12, and iron. Do not start any vitamin or mineral supplements without speaking with your health care team first.

Low blood cell counts can also raise your risk of foodborne illness. Always follow good food safety practices. Visit the Government of Canada's website to read more about food safety.

Juicing separates juice from the fibre in fruits and vegetables. It is one way to add more vitamins, minerals, and calories to your diet. It is important to remember juice is low in fibre, has no protein, and cannot meet all of your nutrition needs on its own.

Read below if juicing is right for you:

If you feel well, have not lost weight, and can chew and digest food normally, it is best to eat fruits and vegetables whole - in other words, not juiced. That way you do not miss out on the fibre, which helps you:

• Have regular bowel movements (poos)
• Control your blood sugar levels
• Lower your cholesterol
• Stay full and prevent weight gain

Follow Canada’s Food Guide and try to fill at least half your plate with fruits and vegetables at each meal. Once you have made this a habit, add in juicing if you would like. Use more vegetables than fruit in your juice to avoid drinking too many calories, which can make you gain weight.

If you have lost weight or have problems eating, blend your fruits and vegetables in smoothies and soups instead of juicing. This will keep the fibre, and you can add protein and extra calories. Check out Smoothies and Shakes for recipe ideas and speak to a dietitian on your health care team to make sure you are meeting your nutrition needs.

If you have been told to follow a low-fibre diet by your doctor or dietitian, you may need to avoid certain whole fruits and vegetables. In this case, juicing is a great choice. Ask your dietitian about lower-fibre plant foods, too, so that you can still eat some fruits and vegetables whole.