Nutrition and Dietetics, University of Queensland, Queensland.
Evidence-based nutrition practice began in Australia in the late 1990s. An editorial by Truswell addressed the issue of quality of nutrition information.1 In 2010 the Board of Directors of the International Confederation of Dietetic Associations approved the following definition of evidence-based dietetics practice as a new international standard: “Evidence-based dietetics practice is about asking questions, systematically finding research evidence, and assessing the validity, applicability and importance of that evidence. This evidence-based information is then combined with the dietitian’s expertise and judgment and the client’s or community’s unique values and circumstances to guide decision-making in dietetics.”2
Ideally, nutrition recommendations should be based on the highest level of evidence. For example, high quality randomised control trials showing the intervention has a beneficial and clinically important effect on relevant outcomes. This is often difficult, if not impossible to achieve in nutrition interventions. In contrast to drug trials, nutrient trials do not involve xenobiotics. This has particular importance for the design of nutrition trials for several reasons. Ethical practice requires, during the informed consent process, that the dietary component under examination be revealed to study participants. A unique difficulty encountered in nutrition trials is that the dietary component being studied may be readily available to participants. This is illustrated in a large international trial evaluating the effect of eicosapentaenoic acid (EPA) in pancreatic cancer.3 From analysis of plasma EPA levels, 18% of participants in the control group had high levels of EPA, indicating they consumed fish oil and in the active group, 26% maintained they were taking the supplement when EPA levels indicated they were not. This is entirely understandable given the prognosis of pancreatic cancer. However, such circumstances do not help the intent to treat analysis of such studies.
Observational epidemiological studies have been used to associate dietary intake with diseases such as cancer. It has often been the case that nutrients of promise have not shown to be of benefit, or indeed have been found to be harmful in subsequent randomised control trials. The β-carotene and lung cancer trials fall into this category. β-carotene, alone or in combination with vitamin E or retinyl palmitate, increased the incidence of lung cancers and the total and cardiovascular mortality rates.4,5 Diets are complex and the addition of one dietary component may affect the bioavailability of other dietary components. The form of the nutrient under study, whether consumed as a supplement or as a whole food, may also influence results. Any test diets must be matched for energy and macronutrients and can be difficult to construct. It may therefore be difficult to demonstrate a therapeutic effect for a nutrient in comparison to a drug, as the effect size of the nutrition intervention may be quite small. The choice of a reliable placebo for comparison purposes may be very difficult, if not impossible to achieve.
Despite these methodological challenges, Australian dietitians have made a substantial contribution to the body of evidence in oncology. The Malnutrition Screening Tool, developed to identify patients at risk of malnutrition, is now the most common nutrition screening tool used in Australia and is recommended as the nutrition screening tool of choice by the American Dietetic Association.6 The nutrition assessment tool, the Patient Generated Subjective Global Assessment, was validated by Australian dietitians and is used internationally as a nutrition assessment tool for oncology patients.7 One of the key features of this tool is the inclusion of symptoms which may impact on dietary intake, such as poor appetite, taste changes, constipation, vomiting, diarrhoea etc. Taste and flavour disorders in patients with cancer are discussed in this issue by Boltong et al.8 They recommend a taxonomy of taste, flavour and food hedonics be developed to improve identification and better inform intervention strategies. In 2004, the first randomised control trial to demonstrate nutrition intervention improves outcomes for patients receiving radiotherapy to the head, neck and gastrointestinal region was published.9 Several studies have confirmed associations between nutritional status, weight loss, treatment toxicities and outcomes.10-12 Evidence-based guidelines for the nutritional management of malnutrition, cancer cachexia and radiation therapy have been published.13-15 Isenring et al highlight there is high level evidence to demonstrate that nutritional counselling of patients receiving radiation therapy improves nutritional status and quality of life outcomes.16 They also review the role of specialised nutritional support using immunonutrition.
New ground has been broken with the online publication using the wiki platform ofEvidence Based Guidelines for the Nutritional Management of Head and Neck Cancer.17 The wiki platform will ensure the guidelines are accessible and remain current. Brown and Findlay report on the current Australian situation in regard to the nutritional management of head and neck cancer patients.18 As expected, there is a diversity of practice as well as diversity of staffing, both of which will impact the implementation of the new guidelines.
Chapman and colleagues describe the role of nutrition for cancer survivors.19 The evidence in relation to body weight, dietary factors and alcohol are presented with emphasis on adoption of a healthy lifestyle. Breast cancer risk and outcomes for breast cancer survivors are known to be influenced by body composition. McDonald et al discuss body composition and breast cancer prognosis, emphasising the potential role that lean body mass and omega-3 fatty acids intake may play.20 In continuing with this theme, Wright and colleagues review the limited evidence supporting the role of diet on prostate cancer progression.21
Improving the dietitian’s knowledge of evidence-based practice related to complementary therapies formed the basis for the Morey and Brown review regarding nutritional supplementation as a complementary and integrative therapy during oncology treatment.22 Mentoring and professional support are essential for healthcare professionals in rural and remote locations. Kiss et al demonstrate how support programs in cancer nutrition have improved confidence, facilitated skill development and built professional networks for rural and remote dietitians in Victoria, Queensland and Western Australia.23
This is the first edition of Cancer Forum to be devoted to nutrition. The papers demonstrate the diversity of oncology nutrition research currently being undertaken, which encompasses nutrition intervention during treatment and survivorship, the application of evidence to practice and the role of mentoring. There is growing interest in the role of nutrition throughout the cancer journey from patients and their carers. Aspects of nutrition are likely to be a topic of conversation with many members of the multidisciplinary team. All health professionals can play a role in advocating for evidence-based nutrition choices and healthy lifestyle modification.
2. International Confederation of Dietetic Associations. Evidence-based dietetics practice. [Internet]. International Confederation of Dietetic Associations; 2010. [cited Retrieved 2011 March 5]. Available from: http://www.internationaldietetics.org/International-Standards/Evidence-based-Dietetics-practice.aspx
3. Fearon KCH, Von Meyenfeldt MF, Moses AGW, Van Geenen R, Roy A, Gouma DJ, et al. Effect of a protein and energy dense n-3 fatty acid enriched oral supplement on loss of weight and lean tissue in cancer cachexia: A randomised double blind trial. Gut. 2003;52:1479-86.
4. Goodman GE, Thornquist MD, Balmes J, Cullen MR, Meykens Jr. FL, Omenn GS, et al. The beta-carotene and retinol efficacy trial: Incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping β-carotene and retinol supplements. J Natl Cancer Inst. 2004;96:1743-50.
5. Omenn GS, Goodman GE, Thornquist MD, Balmes J, Cullen MR, Glass A, et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med. 1996;334:1150-5.
10. Read JA, Beale PJ, Volker DH, Smith N, Childs A, Clarke SJ. Nutrition intervention using an eicosapentaenoic acid (EPA)-containing supplement in patients with advanced colorectal cancer. Effects on nutritional and inflammatory status: A phase II trial. Support Care Cancer. 2007;15:301-307.
11. Oates JE, Clark JR, Read J, Reeves N, Gao K, Jackson M, et al. Prospective evaluation of quality of life and nutrition before and after treatment for nasopharyngeal carcinoma. Arch Otolaryngol Head Neck Surg. 2007;133:533-40.
12. Hill A, Kiss N, Hodgson B, Crowe TC, Walsh AD. Associations between nutritional status, weight loss, radiotherapy treatment toxicity and treatment outcomes in gastrointestinal cancer patients. Clin Nutr. 2011;30(1):92-8.
13. Watterson C, Fraser A, Banks M, Isenring E, Miller M, Silvester C, et al. Evidence based guidelines for nutritional management of malnutrition in adult patients across the continuum of care. Nutrition and Dietetics. 2009;66(Suppl.3):51.
15. Isenring E, Hill J, Davidson W, Brown T, Baumgartner L, Kaegi K, et al. Evidence-based practice guidelines for the nutritional management of patients receiving radiation therapy. Nutr Diet. 2008;65(Suppl 1):S1-S18.
17. Findlay M, Bauer J, Brown T, Davidson W, Hill J, Isenring E, et al. Evidence based practice guidelines for the nutritional management of patients with head and neck cancer. [Internet] Clincial Oncological Society of Australia;2011. [cited 2011 March 5]. Available from: http://wiki.cancer.org.au/australia/COSA:Head and neck cancer nutrition guidelines