Joanna Injore is a Registered Dietitian with over 15 years of experience within the NHS. During the last 10 years of her career in the NHS, she specialised in oncology and led the Dietetic Haemato-oncology Service in a large bone marrow transplant centre in the UK. Joanna currently works as a Freelance Dietitian and also works part-time for Macmillan Cancer Support. Joanna has helped AYMES to put together this oncology nutrition myth-busting article.
When patients are undergoing cancer treatment, nutrition can often feel like the only thing that they have control over. Some patients feel that making decisions about their diet is an opportunity to positively influence their treatment. So, it is understandable that patients may want to try different foods or diets if they think it could help them. However, unfortunately some patients receive non evidence-based nutritional information.
Food is constantly in the media spotlight. We are inundated with messages that we should follow a new diet or avoid specific foods and food groups. It is not surprising that the general public are confused about where to go for accurate information. New scientific studies on food and nutrition are often highlighted in the media, however they omit important scientific detail or are presented in a format which does not reflect the true picture. Since cancer patients are at high risk of malnutrition and weight loss, it is important that any dietary changes are discussed with their medical team. Dietetic input can be provided to ensure nutritional adequacy and patient safety.
Weight loss at diagnosis is very common. It is thought to affect 15-40% of cancer patients1 and it is often a key characteristic that prompts the patient to seek medical advice. During chemotherapy treatment, more than 50%1 of patients experience nausea, vomiting and mucositis, all of which could lead to reduced food intake and weight loss.
Nutrition risk screening2 is important for preventing and addressing weight loss. Oncology dietitians monitor their patients closely and provide nutrition support advice if their dietary intake is being affected due to treatment side effects or the disease itself. If dietary inventions (such as food-first advice and/or oral nutrition supplements) are started early on in the patient’s treatment journey, weight loss can be prevented or at least reduced.
Cancer patients commonly experience poor appetite as a result of both the treatment regimen and the disease itself. Other factors which contribute to poor appetite include low mood or anxiety. Mental health problems are common in cancer 3patients due to the intensive treatment regimen and the interruptions to day-to-day life. Dietitians can support patients with symptoms such taste changes, nausea/vomiting, gastro issues and early satiety by recommending appropriate dietary changes. For example, dietitians may recommend high-energy diets, food fortification techniques or oral nutritional supplements. They may also liaise with the medical team to discuss pharmaceutical management of these symptoms. This multidisciplinary team approach can help to support patients when experiencing appetite changes during treatment.
There are many myths about ‘superfoods’ or ‘anti-cancer’ foods that supposedly prevent or ‘cure’ cancer. Unfortunately, the majority of these claims are not supported by scientific evidence. The term ‘superfood’ has no scientific basis,4so it is open to interpretation by anyone. Furthermore, limiting certain foods or food groups could lead to an unbalanced diet, putting the patient at increased risk of weight loss and malnutrition. There are recommendations for cancer prevention or recurrence based on a healthy and balanced dietary approach, which focuses on whole foods and lifestyle changes. These recommendations are based on a collection of scientific studies from around the world. You can read more about this at the World Cancer Research Fund (details below).
Good nutrition is vital for cancer patients. Cancer patients are at an increased risk of malnutrition and it has been estimated that 10-20% of cancer deaths can be attributed to malnutrition rather than the disease itself 5. Malnutrition in cancer patients is also associated with poor outcomes such as increased infections, treatment toxicity and poor quality of life 5. Therefore, nutrition should play a central role in cancer treatment.
High doses of vitamins and minerals are not recommended for the general public. Most people can get all the nutrients required from eating a healthy and balanced diet. Taking high dose supplements without medical supervision could be particularly dangerous for cancer patients, as some micronutrients and herbal remedies can interfere with certain medications. There may be some situations where vitamins/mineral supplements are recommended, for example if nutritional deficiencies are identified1. In this instance, individual nutritional supplementation should be assessed on a case-by-case basis by a suitably qualified healthcare professional (HCP).
Research into specific vitamins and minerals and cancer outcomes has shown little effect on cancer risk. For example, a high-quality Cochrane review of selenium 6 supplements found that it did not reduce cancer risk. In fact, there was an association with selenium supplements and high-grade prostate cancer.
The myth around sugar being harmful for cancer patients comes from early in vitroresearch. These test-tube studies found that cancer cells thrived when given glucose 7. This fuelled the notion that reducing dietary sugar intakes would prevent cancer cells from growing. However, looking at cancer cells in a laboratory setting is quite different to investigating cancer in the human bodies. Therefore, we cannot apply findings from test-tube studies to humans until further research is conducted. It is also important to note that all human body cells require glucose to function.
A lot of human studies in cancer patients have looked at ketogenic diets; a high-fat and low-carbohydrate diet. The rationale behind this approach is that a ketogenic diet results in a lower blood glucose level, thereby depriving the cancer cells of their energy source. However, a large review 8 of studies in this area found limited evidence for ketogenic diets in cancer patients. The ketogenic diet is a restrictive diet which could result in weight loss or unpleasant side effects such as diarrhoea and constipation, vomiting or fatigue8.
Nutrition advice for patients undergoing cancer treatment is vital. A dietitian is often involved at different points during a patient’s cancer treatment pathway. They will conduct a thorough nutritional assessment to identify any nutritional problems and to ensure that the patient's nutritional requirements can be met throughout their treatment and recovery journey. Dietitians can support patients to reduce or avoid unintentional weight loss and malnutrition by advising on nutrition support techniques, oral nutrition supplements or tube feeding. Dietitians are also able to support patients after treatment to advise on healthy eating and lifestyle and dietary management of long-term side effects of cancer treatment.
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