Rationale and scientific basis

Introduction

Penny Brohn Cancer Care's Healthy Eating Guidelines are the UK’s most comprehensive and well-used set of healthy eating guidelines designed specifically for people with cancer. The guidelines are based on the most up-to-date nutrition research but also the experience of the Penny Brohn Cancer Care therapy team including doctors, nurses, nutritionists and complementary therapists. The guidelines are regularly reviewed and updated if necessary.

The following describes the rationale behind the Healthy Eating Guidelines and explains the science and experiential work on which they are based.

Rationale 

An extensive amount of research has been published investigating the effect of diet and nutrition on cancer prevention. The evidence underpinning the field of nutrition for cancer survivors is not so well developed and to date only a relatively small number of papers have been published focusing on this issue. However, the idea that diet and nutrition may influence the health of people with a cancer diagnosis is emerging as an area of interest amongst scientists and health professionals, recently leading to an increase in the number of publications in this field.

A recent survey carried out by Penny Brohn Cancer Care found that many people with a cancer diagnosis would like to be given dietary guidance and often seek this information for themselves ¹. Other research supports this finding ^{2 3}. While it could be seen as premature to create a set of dietary guidelines for people with cancer in view of the early stages of the research in this area, we feel it is important to provide this group of people with nutritional information for the reasons outlined below.

1. There is a growing recognition that nutrition is important for general health and wellbeing
2. Strong evidence supports the view that diet is an important risk factor for cancer ⁴
3. Studies show that those people with cancer who are well nourished tolerate their medical treatments better than those who are not and that the treatments may actually be more effective in those who are well nourished ⁵
4. Evidence suggests that malnutrition is common amongst cancer patients ⁵
5. People with cancer are at greater risk than the general population of experiencing weight changes – either weight gain or loss ⁵
6. People with cancer are more likely than the general population to develop particular degenerative diseases, such as heart disease and diabetes, the progression of which may be influenced by diet ⁶
7. People with cancer want information on diet and nutrition ¹
8. People with cancer will seek out dietary information if they are not provided with it, the sources of this information are of variable quality ¹
9. Making positive dietary changes helps to give people a sense of control which is a key issue for many people with cancer. This is an observation that has been made by staff at Penny Brohn Cancer Care.

The Target Audience

People with cancer may have very different nutritional needs depending on the stage of their disease and the particular treatments they are having. Penny Brohn Cancer Care Healthy Eating Guidelines have been designed for people with cancer who do not have nutritional needs that require specialist or intensive intervention. Therefore, in their most basic form they are not suitable for people with cachexia or those who have difficulty swallowing, for example. However, they can be modified by a nutritional therapist or dietitian to be suitable for these groups of people.

Survival times for people diagnosed with cancer are ever increasing and the majority of those living with this disease are able to live a relatively normal life. Many of these people are interested in helping themselves to live well with cancer ⁷ and diet can play a significant role in ensuring they achieve this. Penny Brohn Cancer Care Healthy Eating Guidelines are particularly suited to people who want to help themselves as they are easy to follow and do not necessarily require support from a nutritionist or other health professional, although many may benefit from this. 

Scientific Basis for the Healthy Eating Guidelines

Penny Brohn Cancer Care Healthy Eating Guidelines are based on the research looking at diet and nutrition for cancer prevention along with the research focusing on diet and nutrition for cancer survivors.

The diet and cancer prevention data is relevant when considering the nutritional needs of people living with cancer as evidence suggests that some of the mechanisms of primary cancer development are the same as secondary cancer development ⁸. Therefore the diet that helps to prevent a primary cancer is likely also to help prevent a secondary cancer, as well as prevent primary cancer recurrence or further spread of any existing cancer.

The diet and cancer prevention data can not be considered in isolation as cancer survivors often have particular nutritional needs that relate to their disease or its medical treatments. For this reason the research on diet for cancer survivors has also been of key importance in informing these guidelines.

Penny Brohn Cancer Care Research Review Process

Penny Brohn Cancer Care has in place a thorough research review process that is used to assess the published literature in a range of complementary therapy areas. The data generated during this process is created according to the principles of evidence-based medicine and used as a basis for the advice and information given out.

Research literature databases covering both primary and secondary research are searched in a transparent and systematic way. Search results are then carefully filtered and the remaining research is critically appraised according to CEBM (Centre for Evidence Based Medicine) guidelines.

Limitations of Current CAM and Nutrition Research

At the present time there are still large gaps in the complementary and alternative medicine (CAM) research therefore it is impossible to rely solely on the research to support the work carried out at the Centre.

Furthermore, some of the research that has been conducted in the CAM field has not been of particularly good quality and sometimes the trial designs have been inappropriate for applying to the holistic medicine model ⁹. This is because the holistic model involves combining a range of therapies and techniques to support the unique emotional and physical needs of an individual. While it is possible to measure the effects of holistic therapies on health it is often necessary to utilize different trial designs from those regarded as the most rigorous by conventional science, such as the double-blind, randomised controlled trial, which is suited to measuring the effects of a single intervention ¹⁰.
 
These issues apply when considering nutrition research. Diets are composed of many different foods which are made up of many different nutrients and other chemicals. Many of the nutritional intervention trials that have been conducted have followed a reductionist approach and measured the effects of single nutrients on health. Questions have been raised, however, as to whether such data is meaningful and relevant ¹¹. In evaluating the nutritional research it is important to consider as much of the research as possible across all types of study design while being aware of the various limitations.     

Experiential Basis for the Healthy Eating Guidelines 

Thorough evaluation of the research is combined with the experience of the therapy team to provide the basis of the work at Penny Brohn Cancer Care. Thousands of people with cancer have been supported over the past 25 years by the Centre and as a result the team of doctors, nurses, nutritional therapists and complementary therapists have a large amount of experience and knowledge in the area of supportive care for those with cancer.

References

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