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Fighting cancer: Nutrition can help

Fighting cancer: Nutrition can help

Strategies and nutrition information on how to help fight through cancer and its treatments.

Treatments for cancer can be immensely physically challenging, but while your immune system is being knocked around, getting the best possible nutrition can help you fight back. It’s not easy to have the healthiest diet when you are nauseous or find your appetite has gone west. There are strategies that can help, but watch out for the sharks who try to take advantage of you when you’re at your most vulnerable.

When undergoing cancer treatment, you have two key nutrition goals: to maintain a healthy weight and to help fight infection. And once you’ve got through the treatment, your next goal is to maintain your good health. For people used to eating well that might sound pretty straightforward, but there are quite a few possible side effects from cancer treatments that can make healthy eating much more difficult to achieve.

One of the more common side effects is a loss of appetite. Changes in smell and taste can make foods less appealing or even downright disgusting. A dry or sore mouth, thick saliva, or difficulties swallowing can make it difficult to eat certain foods. Both diarrhoea and constipation are also common. Weight gain is another possible side effect, which can be caused by drugs or by a change in eating patterns.  See Top tips for common problems (below) for ideas to overcome these and other issues. And if you do have any of these problems, always tell your medical team as they may be able to help. For example, a loss of appetite could be related to a simple yeast infection that can be easily treated.

If you are able to eat a healthy diet, you’ll be in a better position to cope with the cancer treatment and to fight the cancer. Maintaining a healthy body weight during treatment can help reduce your risk of infection, enhance your speed of recovery, and help maintain your strength and energy. Even losing 5% of your body weight is undesirable, so if you just can’t eat, try using liquid foods like Complan or Ensure.

When you’re dealing with cancer it’s natural to seek information about alternative treatments, including nutritional support and supplements. But do be careful not to turn to supplements or diet programmes that may not provide the nutrients you need to help your immune system and recovery. Professor Lynn Ferguson, head of the Discipline of Nutrition at Auckland University, regularly talks to cancer support groups. She advises you ask these questions about supplements:

  • Is it possible to get the same effect and benefit from food?
  • Will the supplements (herbs/botanicals) interfere with my medications? Have I checked?
  • How much will it cost? Can I cope with the extra costs? Can I still afford to eat properly?
  • Is the person encouraging me to do this likely to make money from me?
  • What does my clinician/oncology nurse say about this?

Professor Ferguson often hears of dubious advice about:

Shark cartilage

“This is often hyped as a cancer treatment yet clinical trials in the US show no positive results. It’s very expensive and – apart from the fact there’s no evidence it helps – a particular concern is that often people use this instead of eating normal good food, because they simply can’t afford to do both.”


There are so many people touting the benefits of so-called ‘detoxing’ and different ways to do it, it’s hard to keep up with. Some are just ‘packaging’ a way of eating a healthy diet, while others tell you to exclude so many foods, they are potentially dangerous. Professor Ferguson advises: “Stick to a healthy diet and beware any plan that wants you to cut out whole food groups.”

Soy versus cow’s milk

There’s a lot of scare-mongering around both soy and cows’ milk. Some claim soy is bad because it contains phytoestrogens. This is despite its long, safe history of use in Asian countries where it’s been associated with reduced risk for hormone-sensitive cancers. Others claim cows’ milk is bad and that it has a high level of hormones and growth factors, like IGF-1.

Professor Ferguson recently undertook a small study into the effects of ‘all-dairy/no soy’ vs ‘all soy/no dairy’ included in women’s normal diets for three weeks. While this is still preliminary data, it was found that neither regime had any effect on IGF-1; there was small but significant weight loss on the soy regime (not helpful for people with cancer); and it was possible, but yet to be confirmed, that the soy milk regime offered some protection from DNA damage.

Much larger trials are needed before any recommendation can be made. In the meantime, it is clear there is no evidence to support the scare-mongering surrounding soy milk or cows’ milk.

What about juicing?

For people having difficulty with solid foods, they may be able to get more nutrients and energy in a liquid form. Only one word of caution: don’t go to the extreme. Juice is not a cure for cancer, as some would have you believe.

Are any supplements advised?

Professor Ferguson notes that for people who cannot eat properly, a multivitamin and mineral supplement is often advised; and where patients are concerned about their bone density, a calcium supplement can be helpful. Remember – any substances you take may interact with your treatment, so it’s important to discuss this with your clinician and/or health nurse. You can also talk to the Cancer Society, visit Dietitians NZ or see your GP to request nutritional advice and support.

Food safety is even more important as you can have a higher risk of infection, and any infection you do get can be more serious. The Ministry for Primary Industries produces a booklet called ‘Food safety when you have low immunity’, which can be downloaded from their website.

Professor Fergusson encourages people seeking information to contact the Cancer Society and find out about their support groups. These groups provide expert advice and up-to-date information from recognised health professionals. She believes some people with commercial interests, pushing their sometimes expensive, unproven supplements, are causing unnecessary distress and confusion for people at a time when they are particularly vulnerable.

“While there are things you can do to help yourself, my main concern is that people don’t go to extremes with their diet. Don’t get carried away with one particular type of food; it can mean you’re excluding other foods that will provide nutrients you need”, says Professor Fergusson. There really is no magic bullet.

Websites for more information

New Zealand Cancer Society
National Cancer Institute
American Cancer Society
American Institute for Cancer Research (see publications/brochures)
Diana Dyer, MS, RD (cancer and nutrition specialist)

In its third expert report released in 2018, the World Cancer Research Fund has these recommendations for the prevention of cancer and for cancer survivors.

  1. Recommendation 1: Be a healthy weight
    It’s easy for weight to creep on over the years but it’s best to avoid this and aim to keep our waist circumference the same throughout our adults lives.
  2. Recommendation 2: Be physically active
    If you’re currently a couch potato it’s ok to start out with smaller goals. But as your fitness improves, set a goal for 60 minutes or more of moderate, or 30 minutes or more of vigorous, physical activity every day
  3. Recommendation 3: Eat a diet rich in wholegrains, vegetables, fruit and beans 
    Aim for at least five serves of a variety of non-starchy vegetables and fruits each day, remembering that more is even better.Choose less processed or unprocessed cereals (grains) and/or pulses with meals. And cut down on those refined starchy foods.
  4. Recommendation 4: Limit consumption of ‘fast foods’ and other processed foods high in fat, starches or sugars
    And the best way to do that? Refer to recommendation 2! You can also plan ahead by checking out our recipes for a homemade version of your favourite takeaway as well as quick, easy meals you can throw together in a rush.
  5. Recommendation 5: Limit consumption of red and processed meat
    Aim for less than 500g cooked (700-750g uncooked) red meat each week (note: this is more than the NZ average intake) and very little if any processed meat (smoked, cured, salted meats).
  6. Recommendation 6: Limit consumption of sugar sweetened beverages
    They’re easy to drink and they don’t fill us up, so they energy (kilojoules) can quickly add up. And they bathe our teeth in sugar! Aim for water to be your first choice for hydration.
  7. Recommendation 7: Limit alcohol consumption
    These are the recommendations to reduce your long-term health risks from drinking alcohol.

    • For healthy women: no more than two standard drinks a day; no more than 10 standard drinks a week; and at least two alcohol-free days per week.
    • For healthy men: no more than three standard drinks a day; no more than 15 standard drinks a week; at least two alcohol-free days per week.

    And of course if you don’t drink there is no good reason to take it up.

    Remember a standard drink is much smaller than you think. All bottles, cans and casks of alcoholic drinks are labelled with how many standard drinks they contain

  8. Recommendation 8: Do not use supplements for cancer prevention
    Dietary supplements are not recommended for cancer prevention. Where possible, aim to meet all your nutritional needs through your diet.
  9. Recommendation 9: For mothers: breastfeed your baby if you can
    Aim to breastfeed infants exclusively for around six months and continue with complementary feeding after they reach 6 months. This is protective for both mother and child.
  10. Recommendation 10: After a cancer diagnosis: Follow recommendations if you can
    Unless otherwise advised, aim to follow the recommendations for diet, healthy weight and physical activity if you’re able to do that.

The report focus was on food, nutrition and physical activity, but it also emphasizes the importance of not smoking and avoiding other exposure to tobacco and excess sun.

It can be very frustrating when the side effects of your cancer treatment interfere with your ability to eat a healthy diet, but there are still things you can do to take control and help yourself.

Low appetite or weight-loss

  • Eat smaller, more frequent meals.
  • If you can only eat a little, choose high-protein, high-energy foods.
  • If your appetite is better in the morning, have your biggest meal in the morning.
  • Drink between meals; drinking with meals may fill you up too quickly.
  • Use liquid or powdered nutritional supplements between meals to increase your energy intake, e.g. Complan, Ensure.
  • Take a walk before mealtimes to enhance your appetite.


  • Drink at least eight glasses of fluids each day to avoid hard stools. Vary with cold or warm water, prune or other juices, black, green or herbal teas.
  • Eat high-fibre foods: fruits and vegetables, legumes and pulses, whole grain breads and cereals.
  • Increase your physical activity.


  • Get plenty of fluids to prevent dehydration; avoid caffeinated drinks.
  • A high-fibre diet may worsen symptoms: try white bread, white rice and noodles instead of whole grains; limit legumes and pulses; peel fruits and vegetables to reduce the fibre.
  • Avoid foods that are spicy, fatty, or very sweet.


  • Keep the diet bland until you can tolerate more: start with clear fluids like juices, sports drinks or soups; progress to soft foods like yoghurt or mashed potato.
  • Keep your fluid intake up to avoid dehydration.


  • Sip fluids frequently to help settle your stomach.
  • Eat smaller, more frequent meals: not eating at all can worsen nausea.
  • Avoid fatty, spicy or high-fibre foods as well as gas-producing foods (like beans, onions, carbonated drinks and chewing gum).
  • Eat sitting up; avoid lying down after a meal, unless the head is elevated.

Difficulty swallowing

  • Aim for small, frequent, high-energy, high-protein meals in a tolerable consistency: cook foods until soft; cut foods into small pieces or purée; make stews and casseroles with thin sauces; moisten foods with spreads, sauces or dressings.
  • Eat food cold or at room temperature if warm foods are irritating.
  • Use a straw for drinks.

Dry mouth

  • Tart drinks like lemonade or orange-flavoured soft drinks may help saliva production.
  • Avoid salty foods.
  • Moisten foods with spreads, sauces, dressings or gravies, or take a sip of fluid with each mouthful to help with chewing and swallowing.
  • A straw may help to ensure you drink plenty of fluids.

Taste changes

  • Try new flavours; use different marinades, sauces, herbs and spices.
  • Decrease the smell of food by serving cold or at room temperature.
  • Add a little sugar to bitter or salty foods; add a pinch of salt to over-sweet foods.
  • Keep your mouth clean by brushing and rinsing regularly; rinse with a baking soda mouth rinse: this will help keep your mouth clean without irritating a dry or sore mouth – dissolve 1/4 teaspoon baking soda in 250ml water.

Unintentional weight gain

  • Check weight gain is not fluid retention caused by drugs; discuss with your clinician.
  • Weight gain can occur when appetite increases, physical activity decreases, or food choices change. The advice is the same as for anyone needing to lose weight: focus on consuming a healthy diet, rather than dieting; take care with portion sizes; and consider increasing exercise.
First published: Dec 2007


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