The Cancer Council of Australia and the New Zealand Cancer Society: first Australasian nutrition, physical activity and cancer conference, Sydney, 24-26 June 2002. (Eat and Run).

The first Australasian conference examining the links between nutrition, physical activity and cancer was held in Sydney from 24-26 June 2002. The Eat and Run conference was an initiative of The Cancer Council Australia and The New Zealand Cancer Society, and was hosted by The Cancer Council New South Wales.

With a few notable exceptions, cancer organisations have been reluctant to actively engage in the public health pursuits of promoting healthy eating and increased physical activity. This is largely because the evidence for causal links between cancer and physical activity, diet and body weight have remained unclear.

Delegates at the Eat and Run conference heard that this is changing. While there is undoubtedly more that research can reveal about the nature and mechanism of these links, a connection between obesity and overweight and various key cancers is now unequivocal. So too, is the link between colon cancer and physical inactivity. So much so that Harvard Professor Graham Colditz, principal investigator of the famous Nurses Health Study, suggested many colleagues saw colon cancer and physical activity as being the most clearly established and consistent cancer/lifestyle risk factor association known to science, after tobacco smoking and cancer.

The three-day conference had daily themes of nutrition and cancer; physical activity and cancer; and obesity and cancer.

Day One--nutrition and cancer

Dr Elio Riboli, head of the Nutrition and Cancer Research Unit of the World Health Organisation's International Agency for Research on Cancer, opened the meeting with a summary of key findings on nutritional factors and cancer outcomes from the European Prospective Investigation into Cancer and Nutrition (EPIC) study.

EPIC is a multi-centre prospective cohort study which was initiated in the mid-1990s. The study is designed to investigate the relationship between food, nutritional status, various lifestyle and environmental factors and the incidence of and mortality from different forms of cancer with, in addition, the potential to investigate mortality from other causes (e.g. myocardial infarction, stroke and other chronic diseases). EPIC embodies five key features:

Large sample: This is a substantial study, encompassing 522 000 participants. At the point of reporting 16 000 newly incident cancer cases have been reported, and over 25 000 are expected to occur by 2005.

Diverse population: The total cohort consists of subcohorts recruited in 23 regional centres in ten European countries (Denmark, France, Germany, Greece, Italy, Netherlands, Norway, Spain, Sweden, United Kingdom) allowing comparisons between areas with very different rates of cancer occurrence and distribution of lifestyle and food habits.

Good baseline information: Food consumption and lifestyle personal data, as well as anthropometric measurements, were collected from all subjects at the time of enrolment in the cohort (mostly between 1994 and 1998).

Measures to maximise data quality: In addition to the dietary measurements obtained from all study subjects, a new method was implemented in EPIC aimed at calibrating dietary measurements across countries, consisting of a second dietary measurement, taken from a 7% random sample of the cohort (38 000 subjects) using a computerised, highly standardised 24-hour diet recall method (EPIC-SOFT).

Objective measures: Biological samples were collected from over 400 000 subjects at enrolment (plasma, serum, leukocytes, erythrocytes) and have been stored in liquid nitrogen (-198 [degrees]C) and will be used for genetic, metabolic, biochemical and epidemiological investigations of cancer causes and mechanisms.

Colorectal or bowel cancer is generally believed to be most subject to dietary influences, with nutritional factors considered to be potentially either causative or protective. This is the focus of a substantial proportion of the diet and cancer related research. The EPIC data suggested the link between processed meat and colorectal cancer warranted further investigation, while also suggesting that fish consumption may provide some protective effect.

The fruit, vegetables and cancer issue remains a challenge as data were not consistently pointing to a protective effect among high consumers. There is likely to be more important information to be released on this issue over the coming years as the EPIC study matures.

Associate Professor Dallas English, from The Cancer Council Victoria, presented early data from the Melbourne Collaborative Cohort study. This is a prospective cohort study of 41 247 people (16 961 men) aged 40-69 years at baseline. Recruitment occurred between 1990 and 1994. Southern European migrants to Australia were deliberately over-sampled to extend the range of lifestyle exposures and to increase genetic variation. Approximately one third of the cohort was born in Italy or Greece. By 23 July 2001, the study identified 543 cases of female breast cancer, 441 cases of prostate cancer and 386 cases of bowel cancer. No other cancers were sufficiently common for analysis.

To quote Dallas English directly:

Meat consumption was positively associated with risk of bowel cancer and, to a lesser extent, breast cancer. For bowel cancer, subjects in the highest category of consumption had a 1.75-fold increased risk. Associations with bowel cancer were also seen for red meat and processed meat. Vegetable consumption was not significantly associated with any of the cancers, although there was a weak negative association with bowel cancer. No significant associations were seen for green leafy or cruciferous vegetables. Fruit consumption showed a weak but significant negative association with risk of breast cancer. In the highest consumption category, the rate ratio was 0.72.

The meat and cancer issue will not go away and deserves a close following.

Among other highlights were presentations by Australian public health nutritionist, Dr Rosemary Stanton. 'Eat less and move more' is a simple and understandable theme that she is keen to promote. Her key points were:

1. Stop advertising junk foods when children are the main viewing audience

2. Tax junk foods to create funds for public health nutrition interventions

3. Ban sales of junk foods from school canteens

4. Increase the nutrition information on food products

5. Lobby for dietary guidelines to be more definitive, including advice to 'eat less' and

6. Stand up and speak out.

Public health consultant and well known nutrition campaigner, Margaret Miller convened a thorough exploration of the available evidence on intervention efficacy across various settings, with some good evidence supporting long-term campaigns of the type run in Western Australia through the 1990s.

Dr Lyn Roberts of the National Heart Foundation of Australia spoke about the 'lessons from the trenches' based on the long history of her organisation's activity in public health nutrition, including a close relationship with the food industry via the Pick the Tick program and other initiatives.

Contributions from New Zealanders Paula Dudley and Diana O'Neill showed that others can learn from the investment and creativity displayed by our colleagues in the region. The Push Play campaign and the Green Prescriptions exercise referral scheme through General Practice have achieved admirable penetration and dissemination throughout New Zealand and offer some useful models worth replicating.

Day Two--physical activity and cancer

The second day brought together thorough and challenging summaries of the epidemiological evidence from Harvard Professor Graham Colditz.

Professor Colditz presented evidence from a series of longitudinal studies starting with the famous Nurses Health Study, which includes repeated measures of physical activity. These studies provide an important resource to assess the role of physical activity in cancer incidence. The Harvard Alumni Study showed an early relation between activity and lower risk of colon cancer. Further, men who increased their level of activity in mid-life had a lower risk of colon cancer during subsequent follow-up.

A review of the evidence to date on the protective effect of physical activity and cancer indicates there is a convincing moderate (RR = 0.51-0.75) effect on colon cancer and a convincing but small (0.76-0.9) effect on breast cancer. There is also a probable and moderate protective effect for endometrial cancer, and a possible and moderate effect on lung cancer, and a possible and small effect on prostate cancer. Clear estimates of the quantum of physical activity necessary to achieve these beneficial effects remains elusive.

In more recent research among men and women health professionals, leisure time physical activity was measured and related to cancer incidence and mortality. Measurement validity studies have been undertaken as a part of the work. Among women the predominant activity is walking. Using established instruments, walking speed is also measured. Total activity, walking, and strenuous activity are each evaluated in relation to colon cancer risk. Among both men and women risk of colon cancer declines steadily with increasing levels of activity. For each additional half hour of activity per week above a moderate baseline, risk of colon cancer is reduced by approximately 10%. Risk of polyps, a precursor lesion for colon cancer, declines with walking pace among women who engage in no strenuous activity.

Breast cancer risk is inversely related to activity level, but the timing of this relation remains unclear. It is possible that activity levels may need to be sustained over a long time to gain a benefit of reduced breast cancer.

Mechanisms for these relations between activity and cancer are unclear. Growing evidence suggests insulin and insulin-like growth factor are a possible mediator for activity and colon cancer. For breast cancer, proposed mechanisms suggested include hormonal and immune function, but little evidence is available.

Australian epidemiologist, Professor Adrian Bauman discussed the state of physical activity interventions, and summaries of physical activity and women (from Professor Wendy Brown), men (Dr Gary Egger) and children (Dr Stewart Trost) put some clear solutions on the table. Most speakers were keen to point out the more general public health benefits of arresting the decline in levels of physical activity. Benefits are to be gained by reductions in cardiovascular disease, diabetes and other chronic disease, as well as a boost in quality of life and mental health, all associated with higher levels of physical activity. To quote Adrian Bauman:

Physical activity is a complex and multi dimensional behaviour. This becomes even more complicated with different domains of physical activity, such as occupational activity, leisure and recreational activity, domestic chores and yard work, and incidental physical activity all may have a health benefit.

Challenges exist in adequately measuring levels of activity, reliably monitoring population trends and then successfully intervening with a view to increasing activity to healthy levels. There is also a debate about how much is enough. Some research suggests levels sufficient to protect against cardiovascular disease may not be sufficient to prevent cancers. While these challenges exist, it seems one factor remains indisputable--the cancer prevention cause is served by promoting higher levels of physical activity in the community, and particularly by promoting public policy which facilitates this outcome.

Professor Neville Owen, Director of the Queensland Cancer Prevention Research Centre, managed an active discussion among expert opinion leaders on the question 'what is stopping us from doing something about physical activity and cancer?'. Common issues of resource availability and priority setting were raised, as were the challenges of--'what are the correct messages to promote?'. None of the discussion however, countered the position above, that is, evidence is clear that action is needed and cancer organisations have a role to play.

Practitioners also reported on current progress. The Western Australian 'Find 30' and 'Two fruit 'n' five veg everyday' campaigns attracted support and aroused interest in the post-campaign evaluation, which is yet to come.

Day Three -- obesity and cancer

This day's marathon session on obesity removed any lingering doubt about the legitimacy of cancer organisations' need to play a role in obesity and weight control programs. Dr Elio Riboli explained:

The relationship between overweight and obesity and the aetiology of diabetes and cardiovascular diseases has been known for long time, while for cancer, it was thought until recently, that the association was limited to some female cancer, endometrium and, possibly breast. Increased risk is now being found also for cancer of the colorectum and kidney, and it has been confirmed for postmenopausal breast cancer and for endometrial cancer at any age.

Mechanisms explaining this effect have been postulated, focussing on the complex metabolic disorders associated with sedentary life-style, overweight and, possibly, some aspects of the so-called, western-style diet. These mechanisms turn around the insulin resistance syndrome, a very common disorder consisting of the overproduction of insulin intended to compensate the decreased insulin sensitivity of peripheral tissues.

The combination of hyperinsulinaemia, overweight and lack of physical activity may represent a major risk factor for several cancer sites and that these factors may explain a substantial proportion of the differences in cancer incidence existing between economically developed and developing countries.

Professor Ian Caterson, Dr Tim Gill and Professor Boyd Swinburn presented the Australasian view of the need for immediate action on obesity. No-one could have left the meeting without a feeling of urgency to tackle the task of turning the last decade of planning documents and reports on the topic into genuine and effective action. Ian Caterson pointed out that:

In 1980 the prevalence of obesity was 8% in adult females and this increased to 21.8% in 2000. In males, the prevalence was 9.3% in 1980 and 19.1% in 2000. Overall obesity prevalence is 20.5% in Australian adults. In men, 67.4% have a BMI > 25 and in women the corresponding figure is 52%. The greater part of the increase in obesity has been since 1989. Over this time, obesity in children has also increased. On examining three large studies of Australian children, it appears that 5-6% of girls and 5% of boys are now obese and 16-18% of girls and 14-16% of boys are overweight. The proportion overweight and obese has doubled in the last ten years.

Dr Katrine Baghurst, Neville Owen and Professor Swinburn laid out the research agenda, and offered pointers on priority research fields, along with a challenge to cancer organisations to push research funding into this sphere of endeavour. Several presenters emphasised the need for research on behaviour, intervention efficacy, policy, and economics to complement the epidemiological work in the field.

Workshop sessions engaged delegates in some challenging issues, from the ethical issues of industry sponsorship to the assessment of food guides and their role as public education tools.

Outcomes

A fiery wind-up session aimed at determining the next steps toward progress led to a recommendation for the establishment of a well-resourced, NGO-funded and driven 'ASH'-(Action on Smoking and Health) style advocacy agency, as well as a special network to push healthy public policy in nutrition and physical activity.

In a conclusive 'round robin' from the panel during this session, the following actions were strongly urged and supported by the audience:

* public transport as an environmental strategy to increase activity

* healthy takeaway food as a readily available option

* promoting walking, and investing in structural change to promote walking in communities

* food access (planning of food stores within walking distance in local communities)

* food levies on takeaway/energy dense foods

* lobbying canteens for the sale of healthy food only

* cooperative action across sectors

* equal emphasis on activity and on diet

* community-based programs for increasing physical activity and improving diet

* advocacy to all relevant levels of government regarding the above.

Finally, there was a consensus that more research between the components of diet and health was needed, as well as research into interventions at a community level.

Perhaps a gauge of the relevance of this subject to the people we serve might be taken by the high level of media attention and public interest the conference attracted.

Work in Australia must now be undertaken to help the documents Eat Well Australia, Active Australia and Acting on Australia's Weight evolve into real change for public health gain for this generation and the next.

Progressing this action falls to the Cancer Council Australia Nutrition and Physical Activity Committee, in concert with the many partners and contributors to the meeting--and those with an interest and commitment to these issues can be a part of the solution.

Copies of the key Eat and Run presentations will be available soon at http://www.cancercouncil.com.au/