PREVENTION OF CANCER

Food, Nutrition, Physical Activity and the Prevention of Cancer

                                 A Global Perspective ^* 

Introduction 

In 1997, the World Cancer Research Fund (WCRF), in association with the American Institute for Cancer Research (AICR), produced the first report with the above title. It immediately became recognised as the most authoritative and influential report in its field.

Since the mid 1990’s, the amount of scientific literature on this subject has dramatically increased. With the development of new methods of analysing and assessing evidence, facilitated by advances in electronic technology, the need for a new report became obvious. Thus, in 2001, WCRF International, in collaboration with AICR, commenced a global process resulting in the second expert Report, with the same title.

When the Report was released on 1^st November 2007, it was widely reported worldwide in all media. The following are a selection of the ‘Headlines’ generated:

‘Be thin to cut cancer, study says’

‘Doctors, Dieticians Stand Behind Fat/Cancer Link’

‘CSIRO welcomes World Cancer Research Fund Report linking obesity and cancer’

‘Avoid saturated (animal) fat’

‘There are different definitions of fat’

‘Should bacon become a controlled substance?’

‘Ward off Cancer: Limit Bacon, Alcohol’

‘Cancer study: Scaremongering? Confusing? Yes. No’

‘Cancer report angers Australian meat industry’.

The People Behind the Report

The Report was compiled by 22 of the world’s top researchers in this area, with the support of independent observers. Each scientist brought a special area of expertise to the Report. The Chair of the panel of experts was Sir Michael Marmot, of University College, London, UK.

The Report is the largest study of its kind, and its conclusions are as definitive as the available evidence allows.

The Report is 537 pages long. To access the full report, or the summary, go to dietandcancerreport.org.

In brief, it is a five year investigation into cancer, sifting and analysing evidence dating back to the 1960’s. The panel of scientists examined 7,000 published studies, distilled down from an initial 500,000. Evidence was pooled in a process called Meta-analysis, which picks up subtle trends that might not show up in a single study.

The Panel delivered verdicts on whether individual risk factors had a causal association with different cancers, or a protective effect. The evidence ranged from ‘convincing’ to ‘probable’ to ‘limited-suggestive’ or ‘substantial effect unlikely’.

How the Report was Achieved

The process was designed to maximise objectivity and transparency, separating the collection of evidence from its assessment and judgement.

First, an expert taskforce developed a method for systematic review of the voluminous scientific literature.

Second, research teams collected and reviewed the literature based on this methodology.

Third, the expert Panel assessed and judged the evidence and agreed recommendations.

The resultant Report is “a guide to future scientific research, cancer prevention education programmes and health policy around the world. It provides a solid evidence base for policy-makers, health professionals, and informed and interested people to draw on and work with.”

The Purpose(s) of the Report

The Report has a number of inter-related general purposes. One is to explore the extent to which food, nutrition, physical activity and body composition modify the risk of cancer, and to specify which factors are most important. To the extent that environmental factors such as food, nutrition and physical activity influence the risk of cancer, cancer is a preventable disease. The Report specifies recommendations based on solid evidence which, when followed, will be expected to reduce the incidence of cancer.

The Report is in three parts:

• Part 1 gives the background and this is covered in three chapters. The summary states: “the prevention of cancer worldwide is one of the most pressing challenges facing scientists and public health policy-makers, among others. These introductory chapters show that the challenge can be effectively addressed and suggest that food, nutrition, physical activity and body composition play a central part in the prevention of cancer.”
• Part 2 sets out the Evidence and Judgements: “the judgements made by the Panel are based on independently conduced systematic reviews of the literature commissioned from academic institutions in the USA, UK and continental Europe. The evidence has been meticulously assembled and, crucially, the display of the evidence was separated from assessments derived from that evidence. Eight chapters (four to eleven) present the findings of these reviews”.
• Part 3 gives us the recommendations. “Chapter 12, the culmination of the five-year process, presents the Panel’s public health goals and personal recommendations”. “The goals and recommendations are based on ‘convincing’ or ‘probable’ judgements made by the Panel in part 2”. It is claimed that “if effectively implemented [they] [the recommendations] will be expected to reduce the incidence of cancer for people, families and communities.” “The public health goals and personal recommendations of the Panel (chapter 12) are offered as a significant contribution towards prevention and control of cancer throughout the world.”

The Panel’s Recommendations

• The ‘public health goals’ are for populations, and therefore for health professionals.
• The ‘personal recommendations’ are for people, as communities, families and individuals.
• The Panel also emphasises the importance of not smoking and avoiding exposure to tobacco smoke.

The following are the eight recommendations and two special recommendations. They are presented as verbatim quotes from the summary section of the 537 page Report.

Recommendation 1

BODY FATNESS

Be as lean as possible within the normal range of body weight

PUBLIC HEALTH GOALS

• Median adult body mass index (BMI) to be between 21 and 23, depending on the normal range for different populations
• The proportion of the population that is overweight or obese to be no more than the current level, or preferably lower, in 10 years

PERSONAL RECOMMENDATIONS

• Ensure that body weight through childhood and adolescent growth projects towards the lower end of the normal BMI range at age 21
• Maintain body weight within the normal range from age 21
• Avoid weight gain and increases in waist circumference throughout adulthood

JUSTIFICATION

• Maintenance of a healthy weight throughout life may be one of the most important ways to protect against cancer. This will also protect against a number of other common chronic diseases.

Recommendation 2

PHYSICAL ACTIVITY

Be physically active as part of everyday life

PUBLIC HEALTH GOALS

• The proportion of the population that is sedentary to be halved every 10 years
• Average physical activity levels (PALs) to be above 1.6

PERSONAL RECOMMENDATIONS

• Be moderately physically active, equivalent to brisk walking, for at least 30 minutes every day
• As fitness improves, aim for 60 minutes or more of moderate, or for 30 minutes or more of vigorous, physical activity every day
• Limit sedentary habits such as watching television

JUSTIFICATION

• Most populations, and people living in industrialised and urban settings, have habitual levels of activity below levels to which humans are adapted.

Recommendation 3

FOODS AND DRINKS THAT PROMOTE WEIGHT GAIN

Limit consumption of energy-dense foodsAvoid sugary drinks

PUBLIC HEALTH GOALS

• Average energy density of diets to be lowered towards 125 kcal per 100 g
• Population average consumption of sugary drinks to be halved every 10 years

PERSONAL RECOMMENDATIONS

• Consume energy-dense foods sparingly
• Avoid sugary drinks
• Consume ‘fast foods’ sparingly, if at all

JUSTIFICATION

• Consumption of energy-dense foods and sugary drinks is increasing worldwide and is probably contributing to the global increase in obesity.

Recommendation 4

PLANT FOODS

Eat mostly foods of plant origin

PUBLIC HEALTH GOALS

• Population average consumption of non-starchy vegetables and of fruits to be at least 600 g (21 oz) daily
• Relatively unprocessed cereals (grains) and/or pulses (legumes), and other foods that are a natural source of dietary fibre, to contribute to a population average of at least 25 g non-starch polysaccharide daily

PERSONAL RECOMMENDATIONS

• Eat at least five portions/servings (at least 400 g or 14 oz) of a variety of non-starchy vegetables and of fruits every day
• Eat relatively unprocessed cereals (grains) and/or pulses (legumes) with every meal
• Limit refined starchy foods
• People who consume starchy roots or tubers as staples also to ensure intake of sufficient non-starchy vegetables, fruits, and pulses (legumes)

JUSTIFICATION

• An integrated approach to the evidence shows that most diets that are protective against cancer are mainly made up from foods of plant origin.

Recommendation 5

ANIMAL FOODS

Limit intake of red meat and avoid processed meat

PUBLIC HEALTH GOAL

• Population average consumption of red meat to be no more than 300 g (11 oz) a week, very little if any of which to be processed

PERSONAL RECOMMENDATION

• People who eat red meat to consume less than 500 g (18 oz) a week, very little if any to be processed

JUSTIFICATION

• An integrated approach to the evidence also shows that many foods of animal origin are nourishing and healthy if consumed in modest amounts.

Recommendation 6

ALCOHOLIC DRINKS

Limit alcoholic drinks

PUBLIC HEALTH GOAL

• Proportion of the population drinking more than the recommended limits to be reduced by one third every 10 years

PERSONAL RECOMMENDATION

• If alcoholic drinks are consumed, limit consumption to no more than two drinks a day for men and one drink a day for women

JUSTIFICATION

• The evidence on cancer justifies a recommendation not to drink alcoholic drinks. Other evidence shows that modest amounts of alcoholic drinks are likely to reduce the risk of coronary heart disease.

Recommendation7

PRESERVATION, PROCESSING, PREPARATION

Limit consumption of salt

Avoid mouldy cereals (grains) or pulses (legumes)

PUBLIC HEALTH GOALS

• Population average consumption of salt from all sources to be less than 5 g (2 g of sodium) a day
• Proportion of the population consuming more than 6 g of salt (2.4 g of sodium) a day to be halved every 10 years
• Minimise exposure to aflatoxins from mouldy cereals (grains) or pulses (legumes)

PERSONAL RECOMMENDATIONS

• Avoid salt-preserved, salted or salty foods; preserve foods without using salt
• Limit consumption of processed foods with added salt to ensure an intake of less than 6 g (2.4 g sodium) a day
• Do not eat mouldy cereals (grains) or pulses (legumes)

JUSTIFICATION

• The strongest evidence on methods of food preservation, processing, and preparation shows that salt and salt-preserved foods are probably a cause of stomach cancer, and that foods contaminated with aflatoxins are a cause of liver cancer.

Recommendation 8

DIETARY SUPPLEMENTS

Aim to meet nutritional needs through diet alone

PUBLIC HEALTH GOAL

• Maximise the proportion of the population achieving nutritional adequacy without dietary supplements

PERSONAL RECOMMENDATION

• Dietary supplements are not recommended for cancer prevention

JUSTIFICATION

• The evidence shows that high-dose nutrient supplements can be protective or can cause cancer. The studies that demonstrate such effects do not relate to widespread use among the general population, in whom the balance of risks and benefits cannot confidently be predicted. A general recommendation to consume supplements for cancer prevention might have unexpected adverse effects. Increasing the consumption of the relevant nutrients through the usual diet is preferred.

Special Recommendation 1

BREASTFEEDING

Mothers to breastfeed; children to be breastfed

PUBLIC HEALTH GOAL

• The majority of mothers to breastfeed exclusively, for six months

PERSONAL RECOMMENDATION

• Aim to breastfeed infants exclusively up to six months and continue with complementary feeding thereafter

JUSTIFICATION

• The evidence on cancer as well as other diseases shows that sustained, exclusive breastfeeding is protective for the mother as well as the child.

Special Recommendation 2

CANCER SURVIVORS

Follow the recommendations for cancer prevention

RECOMMENDATIONS

• All cancer survivors to receive nutritional care from an appropriately trained professional
• If able to do so, and unless otherwise advised, aim to follow the recommendations for diet, healthy weight, and physical activity

JUSTIFICATION

• Subject to the qualifications made here, the Panel has agreed that its recommendations apply also to cancer survivors. There may be specific situations where this advice may not apply, for instance, where treatment has compromised gastrointestinal function.

NOTES

Ideal Weight. Maintenance of a healthy weight throughout life may be one of the most important ways to protect against cancer. Be slim, be very slim. The greater your weight, the greater your risk of developing a number of cancers everywhere from the colon and the breast to the prostate, kidney and pancreas.

Excess body fat, lack of exercise, as well as the consumption of alcohol, red meat and processed meats like bacon increase your risk of developing cancer.

“Lower end of the normal BMI range” – the ‘normal’ range, depending on body build is 20-25 (BMI is weight in kg divided by height in metres squared). In ‘How to Live to 100⁺ Years Free from Symptoms and Disease’ (see homepage), I recommend that the range for BMI should be 18-23 for optimal health. The Report suggests 18.5 to 23. “Be slim, be very slim”.

Being overweight (in Australia some 60 percent of the population is now overweight, ie has BMI 25 or greater) not only increases the risk of some cancers, being overweight or obese also increases the risk of conditions including dyslipidaemia (high cholesterol and triglycerides), hypertension, stroke, coronary heart disease and type 2 diabetes.

Physical activity level (PAL). PAL, referred to in recommendation N^o2, is a way of representing the average intensity of daily physical activity. PAL is calculated as total energy expenditure as a multiple of basal metabolic rate. The term ‘sedentary’ refers to a PAL of 1.4 or less. All forms of physical activity protect against some cancers, as well as against weight gain, overweight and obesity.  Energy-Dense Foods.

‘Energy-density’ measures the amount of energy (in kcal or kJ) per weight (usually 100gm) of food. Energy-dense foods are defined in the Report as those with an energy content of more than about 225-275 kcal per 100 g. Food supplies that are mainly made up of processed foods, which often contain substantial amounts of fat and/or sugar, tend to be more energy-dense than food supplies that include substantial amounts of fresh foods.

Non-starchy Vegetables. These include green, leafy vegetables, broccoli and eggplant. Non starchy roots and tubers include carrots, artichokes, celery, suede and turnips.

Starchy Foods. These include potato, yam and sweet potato.

Plant-Foods. ‘Plant-based’ means diets that give more emphasis to those plant foods that are high in nutrients, high in dietary fibre (and so in non-starch polysaccharides), and low in energy density.

The goals and recommendations of Recommendation N^o 4 (plant foods) are broadly similar to those that have been issued by other international and national authoritative organisations. They derive from the evidence on cancer and are supported by evidence on other diseases. They emphasise the importance of relatively unprocessed cereals (grains), non-starchy vegetables and fruits, and pulses (legumes), all of which contain substantial amounts of dietary fibre and a variety of micronutrients and are low or relatively low in energy-density. These, and not foods of animal origin, are the recommended centre for everyday meals.

Animal Foods. The Panel emphasises that the overall recommendation of N^o5 is not for diets containing no meat, or diets containing no foods of animal origin.

Alcoholic Drinks. The recommendation concerning alcoholic drinks (N^o 6) covers all alcoholic drinks, whether beer, wines, spirits (liquors) or other alcoholic drinks. The important factor is the amount of ethanol (alcohol) consumed. ‘One drink’ is either 10 ml of alcohol (eg in UK) or 10 grams of alcohol (eg in Australia).

Aflatoxins. Contamination of cereals (grains) and pulses (legumes) with aflatoxins, produced by some moulds when such foods are stored for too long in warm temperatures, is an important public health problem and not only in tropical countries. Aflatoxins cause liver cancer.

Dietary Supplements. The Panel recognises that there are situations where supplements are advisable. In general, for otherwise healthy people, inadequacy of intake of nutrients is best resolved by nutrient-dense diets and not by supplements, as these do not increase consumption of other potentially beneficial food constituents. The recommendations of this Report, in common with its general approach, are food based. The Panel judges that the best source of nourishment is foods and drinks, not dietary supplements. However, in Western counties, most foods are not grown organically. Also fruits, for example, tend to be picked green and stored, then artificially ripened before being sent to market. As a result, supplements of vitamins, such as C and the B group, would be indicated although not recommended by the Panel.

Conclusion

The Report’s authors say that they have produced a list of recommendations, not “commandments”. Professor Martin Wiseman (Report Author), goes on to say: “But if people are interested in reducing their cancer risk, then following the recommendations is the way to do it…………. Cancer is not a fate, it is a matter of risk, and you can adjust those risks by how you behave. It is very important that people feel that they are in control of what they do”.

Cancer is epidemic. In spite of billions of dollars spent in research, as well as in treatment, the incidence of cancer, and deaths from it, keep on increasing.

The recommendations of the Report, if embraced and enacted, will significantly change the course of cancer and all the suffering associated with it.

The Dietary Guidelines, and other recommendations such as correct weight and exercise, as set out in my book ‘How to Live to 100⁺ Years Free from Symptoms and Disease’ (see homepage), are in complete agreement with the Recommendations of this Report based on the meta-analysis of 7,000 published papers by a Panel of 22 experts over a 5-year period.

It should also be noted that exposure to sunlight and vitamin D are also important in cancer prevention. This is fully discussed in my November 2007 newsletter ‘Sunlight and Health’.

In the words of Professor Michael Marmot (Chairman), the overriding aim of the Report is “to reduce the global burden of cancer by means of healthier living”.                      

                                                    CARPE  DIEM.