Food, Nutrition, Physical Activity and Cancer

20 May 2008

Overview

Scope and source

Cancer burden and causes in EU

Determinants of food, nutrition, overweight and physical activity

Which factors increase or decrease cancer risk

Latest insights and recommendations

Scope and source

A broad range of epidemiologic and other scientific data demonstrate the importance of environmental and behavioral factors in the development of human cancer. This holds in particular for food, nutrition, and physical activity. A better insight into the relevant relationships therefore, may contribute significantly to cancer prevention.

This EUphocus provides an overview of the current state of evidence with regard to cancer prevention (or stimulation) by food, nutrition, physical activity and the related risk factor overweight. It is mainly based on the second WCRF/AICR report (2007) entitled 'Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective', which concludes with a comprehensive set of recommendations.

Cancer burden and causes in EU

Cancer is responsible for about 25% of all deaths in the EU, making it the second cause of death after cardiovascular diseases. There is a difference between the sexes, the number of male cancer deaths being somewhat higher than that of females.

In almost all EU countries the cancer pattern reflects that of the developed countries, with lung, colon/rectum, breast, prostate, stomach, pancreas, bladder and white blood cells as the most predominant sites. In terms of cancer deaths (both sexes combined), lung cancer and colorectal cancer are clearly number one and two. Lung cancer however, is more frequent in the new member states (East Europe, Baltic), while there is no clear gradient observed (north-south, or east west) for colorectal cancer. For the remaining cancer sites the exact ranking order shows some differences between the EU countries.

From the environmental factors, smoking (and other tobacco use) is still the most predominant one. In total it may be causally related to some 30% of all cancer cases and deaths. Regarding food and nutrition, it is now generally believed that dietary factors account for about 30 % of cancers in the EU as well. This is an overall estimate, which clearly varies for different cancer sites. Overweight and physical activity are estimated to account for between 20 and 33 % of cancers of the breast (postmenopausal), colon, kidney, endometrium and oesophagus.

Determinants of food, nutrition, overweight and physical activity

Using specific and concrete definitions for food and nutrition, it becomes clear that nutrition (or diet), is the result of two major determinants, i.e. food supply and eating behaviour. These two determinants are in turn influenced by a range of other determinants. Changes in some of these subdeterminants, like those for food supply, seem to have coincided in the past with changes in cancer patterns.

Nutrition furthermore, involves two important aspects, i.e. quantity (energy intake) and quality (dietary composition). The quantity relates to the energy balance (energy intake minus expenditure). If positive, this may lead to weight gain, overweight and ultimately obesity. The latter two form a risk factor for several chronic diseases, including cancer.

The quality relates to the presence of nutrients (macro and micro), naturally occuring compounds/non-nutrients (a.o. fibre, secondary plant metabolites) and non-naturally occurring constituents like additives or contaminants. A rather complex relationship seems to exist between the different dietary constituents and some chronic diseases, including cancer.

Physical activity activity is the major determinant at the expenditure side of the energy balance. It can prevent weight gain at all ages, thereby decreasing the health risks of being overweight or obese. Also here, the two major determinants concern the supply side and the behavioural side, each with their own set of subdeterminants. Due to urbanisation and industrialisation, the overall levels of physical activity have declined over the past century, in particular (but not exclusively) in high-income countries.

Which factors increase or decrease cancer risk

The WCRF/AICR report (2007) distinguishes different grades of scientific evidence. Only the top two grades (convincing and probable) will be presented in this Euphocus.

Dietary composition

For 6 cancer sites there is convincing evidence of an increased cancer risk by the consumption of certain foods, drinks or food constituents. Four of these (mouth, oesophagus, colorectum, breast) concern alcoholic drinks. The other two (lung, liver) relate to specific carcinogenic contaminants in either drinking water or foods. Also beta-carotene supplements and red meat (or processed meat) convincingly increase the risk of respectively lung and colorectal cancer.

A probably increased cancer risk is found in four additional cancer sites (nasopharynx, stomach, prostate and skin) by the consumption of respectively salted fish, salted & salty foods, high calcium, and arsenic in drinking water

The available evidence for a protective effect against cancer by the consumption of certain foods, drinks and food constituents, is at best judged as ‘probable’. This judgement is made for 7 cancer sites. Four of these (mouth, lung, oesophagus, and stomach) concern the probable protective effects of non-starchy vegetables, fruits, foods with carotenoids and allium vegetables. The other three cancer sites (pancreas, colorectum, and prostate) concern mostly specific food constituents like folate, dietary fibre, garlic, calcium, lycopene or selenium.

Physical activity

Physical activity, besides being protective against weight gain, convincingly protects against colon cancer. It probably also protects against female hormone-related cancers like endometrium and breast cancer (postmenopause).

Overweight and obesity

There is convincing evidence that (excess) body fat increases the risk for six cancer sites (oesophagus, pancreas, colorectum, breast [postmenopause], endometrium, kidney). In addition, a probable increased risk exists for additional cancer types by body fatness (gall bladder), abdominal fatness (pancreas, breast [postmenopause], endometrium) and adult weight gain (postmenopausal breast cancer).

However, body fatness was also found to be probably protective against premenopausal breast cancer.

As a modifier of weight gain, physical activity convincingly decreases the risk of becoming overweight, while sedentary living increases it.

Growth and development

Greater adult attained height convincingly increases the risk of colorectum and breast cancer (post menopause). It probably also increases the risk for ovary and pancreas cancer. The risk of premenopause breast cancer is probably increased by both greater birthweight and greater adult attained height (see chapter 6, WCRF/AIRC 2007).

However, women who were breastfeeding their child were convincingly shown to have a reduced risk of breast cancer at all ages thereafter (both premenopause and postmenopause).

Latest insights and recommendations

The criteria for weighting the strenght of the evidence in the WCRF/AICR report (2007), are more stringent than those used in their previous report (1997). As a result, some known relationships have been downgraded, like for instance the cancer protective effects of fruits and vegetables. But the upgrading of a few protective effects is also observed.

In addition, the total evidence for increased cancer risks by overweight and obesity has become much stronger. Also some some new cancer risks (skin, pancreas, ovary), or new protective effects (colorectum, prostate, endometrium breast) were noted for certain foods or food constituents.

Finally, the review of all available data and the conclusions by WCRF/AICR have also led to a comprehensive set of 10 recommendations. Moreover, the eight general and two special recommendations have also been translated into public health goals for populations (to assist health professionals) and into personal recommendations to guide people (individuals, families or communities).

20 May 2008

Food, Nutrition, Physical Activity and Cancer

Introduction

World Cancer Research Fund (WCRF/AICR)

This Euphocus provides an overview of the current state of evidence with regard to cancer prevention (or stimulation) by food, nutrition, overweight and physical activity. The results are mainly based on the extensive and authorative work carried out by the World Cancer Research Fund (WCRF), in collaboration with the American Institute for Cancer Research (AICR).

In 1997 the WCRF/AICR published its first report (WCRF/AICR, 1997). This report has had a great influence on cancer prevention at all levels. For instance, the methodology developed by WCRF/AICR to classify the strength of scientific evidence was later adopted by WHO in its 2003 report on 'Diet, Nutrition and the Prevention of Chronic Diseases' (WHO, 2003b).

Since the mid 1990’s there has been a dramatic increase in the amount of literature on this subject, in particular concerning the effects of overweight, obesity and physical activity. Also new methods for analyzing and assessing the evidence became available. An update of the first report was therefore needed, and this resulted last year in the publication of a second WCRF/AICR report (2007) entitled 'Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective'. In this new report, the main procedure and special features of the first report have been adapted and further developed. The results obtained in this second WCRF/AICR report served as the major source of information for this Euphocus.

Cancer and environmental factors

Cancer is a chronic disease that poses a major threat to mankind. It affects millions of people worldwide, and current trends, moreover, are unfavourable. Prevalence’s are increasing at a rate faster than the increase in global or EU population.

Cancer comprises over 100 different diseases, depending on the tissue affected. They are all characterized by uncontrolled cell growth due to specific genetic alterations (mutations) that in most cases are caused by the interplay between lifestyle and inborn (individual) genetic predispostion.The cancer pattern (distribution of different cancers) varies between countries/populations. Some cancer types are more common in lower income countries, while others are more common in higher income countries. Also, cancer patterns are found to change in time within countries/populations. For instance if countries become more urbanized and industrialized, or if populations migrate to other countries. Such changes indicate the important role of environmental factors as modifiers of cancer risk.

To date, known environmental factors that can modify cancer risk are: smoking (and other tobacco use); infectious agents; ionizing radiation (x-rays) and UV (A,B); industrial chemicals (and pollution); medication; food, nutrition, overweight (body fatness) and physical activity.

The role of food, nutrition, body fatness and physical activity, is among others supported by the fact that the changes in cancer patterns seem to coincide with the recent changes in patterns of food, drink, and physical activity. With industrialization and urbanization, food supply has become more secure and abundant. Diets contain more energy-dense foods (fats, oils) less vegetables and fruits, and often more alcoholic drinks. At the same time overall levels of physical activity have declined, and the lifestyle of people has become more sedentary. The strong increase in the number of people who are overweight or obese further serves to illustrate these trends.

Cancer, prevention, nutrition and physical activity

More conclusive evidence for the important role of food and nutrition (or specific food constituents), is derived from a broad range of in-depth studies during the past few decennia. These investigations included both epidemiological, intervention, experimental and mechanistic studies. However, not always did such studies yield clear-cut and consistent results. Consequently, conclusions about the strength of evidence for some food-cancer relations, have changed over time.

The combined scientific data concerning food, nutrition, overweight, and physical activity, (but also from other environmental factors), clearly suggest that cancer might be a preventable disease, at least to a certain degree. Thus, the most pressing challenge to date for scientists and health policy-makers is to invent, develop and launch measures that will effectively prevent cancer.

For nutrition this requires first of all, the establishment of clear and undisputed relations between certain nutritional factors and specific cancer types. In this Euphocus, an overview of such relations is presented, based on the recently published WCRF/AICR report (2007). In this report five different and descending categories are used to indicate the strength of evidence. The top two categories ‘convincing’ and ‘probable’ are considered to be the strongest. According to WCRF/AICR both categories justify goals and recommendations designed to reduce cancer incidence. In this Euphocus attention will also be given to those public and personal recommendations in the report. Opportunities for intervention will be discussed in a forthcoming WCRF/AICR policy report, due for publication in late 2008. That report will provide advice and guidance on what can be done to influence and change the lifestyle choices of people, in particular related to their risk of cancer.

22 May 2008

Food, Nutrition, Physical Activity and Cancer

Cancer burden in the EU

General

The WCRF/AICR report (2007) estimates that in 2002 over 10 million new cases of cancer were diagnosed worldwide, and about 7 million people actually died from cancer. Moreover, these figures are expected to rise to 16 million new cases and 10 million deaths by the year 2020.

In the EU-25, there were over two million (ca 2,29 million) incident cases of cancer in 2006 and over one million cancer deaths (ca 1,17 million) (Ferlay et al., 2007). This represented about 25% of all deaths, making cancer the second cause of death in the EU, after cardiovascular diseases. Further, there is some difference between the sexes, the number of male cancer deaths comprising 56% and that of females 44% of the total of cancer deaths.

Current trends indicate a slow overall decline in cancer deaths in the EU for both males and females. This in contrast to the still increasing incidence of some cancers in the EU, like cancer of the prostate, colon, stomach, oesophagus, and lung (females). As a result of current trends and aging populations, the number of cancer deaths in the EU-25 is estimated to 1,25 million in 2015 (Ferlay et al., 2007).

Causes of cancer

About 5-10% of cancers are the direct result from an inherited defective gene (heritable or familial cancer types). Such cancers occur relatively early in life. The vast majority of cancers however, are due to an accumulation of genetic changes in somatic cells during lifetime, which explains their relatively long latency time. The cause of these genetic changes can be both endogenous (internal) and exogenous (environmental).

From the environmental causes, smoking (and other tobacco use) is the most predominant one. It is estimated to be responsible for 85% of lung cancers and 25% of pancreas cancer. But it is also believed to play a role in cancer of the kidney, oesophagus, mouth, larynx, nasopharynx, and pharynx. In total it may be causally related to some 30% of all cancer cases and deaths.

With regard to food, nutrition, overweight and physical activity, it is much more difficult to indicate their relative contributions to the overall cancer burden. In the early 1980’s epidemiologists have estimated that for nutrition (food and drinks) this might be in the order of 35% too. However, the uncertainties in such estimates were great, resulting in a variation from 10-70%.

As new data became available the original estimates have been refined. It is now generally believed that dietary factors account for around 30% of cancers in industrialized countries, and 20% in developing countries. This figure is an overall figure and clearly varies for different cancer sites. Excess body weight and physical inactivity are estimated to account for between 20% and 33% of cancers of the breast (postmenopausal), colon, endometrium, kidney, and esophagus (Global Cancer Atlas).

Differences in cancer deaths within the EU

In a few countries the percentage of all deaths due to cancer seem notably lower than the average 25%. This holds in particular for the Baltic states, and some east-European countries. In these countries, however, the relative contribution by cardiovascular diseases and external causes appears to be much greater.

Cancer patterns are similar throughout the EU

In almost all EU countries the cancer pattern reflects that of the developed countries, with lung, colon/rectum, breast, prostate, stomach, pancreas, bladder and white blood cells as the most predominant sites. With the exception of stomach cancer, all these sites show generally a higher incidence in developed countries than in developing countries.

In 2006 in Europe, the three most common form of cancers were breast cancer (429,900 new cases: 13.5% of all new cancer cases), colorectal cancers (412,900: 12.9%) and lung cancer (386,300: 12.1). Lung cancer, with an estimated 334,800 deaths (19.7% of total), was the most common cause of death from cancer, followed by colorectal (207,400 deaths), breast (131,900) and stomach (118,200) cancers (Ferlay et al., 2007).

There are differences between EU-countries with regard to the ranking of the sites. In terms of cancer deaths (both sexes combined), lung cancer and colorectal cancer are clearly number one and two. Lung cancer however, is more frequent in the new member states (East Europe, Baltic), while there is no clear gradient observed (north-south, or east-west) for colorectal cancer.

For the remaining sites the ranking order shows differences per country, i.e. breast and prostate cancer are not always the third or fourth most common cancer site in terms of cancer deaths. For instance, stomach cancer kills more people in the Baltic and some Balkan states, and is also the third most common cancer in Poland, Spain and Portugal. Prostate cancer is the third most common cancer site in Sweden, and also more frequent in Finland and Baltic states. Breast cancer, however, is relatively more frequent in Denmark, Belgium and the Netherlands.

20 May 2008

Food, Nutrition, Physical Activity and Cancer

Determinants of food, nutrition and physical activity

General

Determinants of food and nutrition

Two important aspects of nutrition

Physical activity: role and determinants

General

Food and drinks are essential to human life and physical function. In all life phases, from conception to old age, an adequate quantity and composition of our food is essential.

Thus, a variety of nutrients is required in order to provide energy, regulate bodily functions and enable regeneration of cells and tissues.

A distinction is made between macronutrients and micronutrients. The macronutrients are found in higher quantities in the diet and provide most of the energy (carbohydrates, fats, proteins, alcohol). The micronutrients (vitamins, minerals, trace elements) are more involved in the regulation of bodily functions and regeneration.

Besides nutrients, a lot of other naturally occurring constituents are present in foods. These ‘non-nutrients’ comprise among others water, fibre, secondary plant metabolites and anti-nutritional factors.

Furthermore, a variety of non-naturally occurring constituents may also be present in foods. This includes several categories of additives (e.g. preservatives, colourings, flavourings agents) as well as microbial or chemical contaminants.

Definitions of food and nutrition

The terms ‘nutrition’ or ‘diet’ are subject to different interpretations in the EU, varying from broad to very narrow definitions. For pragmatic reasons, specific and concrete definitions have been adopted for nutrition and food in this Euphocus. These definitions (see table) prove very helpful in understanding and recognizing the important (sub)determinants of food and nutrition.

Term

Definition *

Food

Variety of foods made available by hunting, agriculture, and food processing industry.

(i.e. all products available to the general public)

Nutrition

(= diet)

Total consumption of food and drinks by an individual or a population, expressed in terms of specific foods and drinks, or in nutrients and other food constituents.

(i.e. what is actually consumed)

* According to the Dutch report: Our food, our health (2006)

Determinants of food and nutrition

Using the above definitions, it becomes clear that nutrition (or diet) is actually the result of two major determinants:

1. Food supply (range and quality of products available)

2. Eating behaviour of people (food choices, food preparation)

But these two determinants of nutrition are themselves under the control of a broad range of other (sub)determinants, as also noted in the WCRF/AICR report (2007). These concern important factors like:

a. Type of society (gatherer-hunter, peasant-agriculture, or urban-industrial)

b. Globalization and food technology

c. Health policy (protection and promotion)

d. Social environment: socio-economic and personal determinants of behaviour

Interestingly, historical and recent changes in some of the subdeterminants of food supply seem to coincide with significant changes in the rates of most common cancers. Together with the change in cancer patterns observed in immigrant populations, this indicates that environmental factors (including nutrition) play an important role in the cause of cancer. Moreover, it also suggests that cancer is a preventable disease at least to a certain degree.

Two important aspects of nutrition

Regarding the health effects of nutrition, a distinction must be made between two important aspects:

1. Quantity: in terms of energy intake

2. Quality: in terms of dietary composition

If the intake of energy-providing nutrients is too low, the result will be malnutrition and eventually starvation. However, if overall energy intake is too high (i.e. exceeding energy expenditure), this will lead to weight gain, which may result in overweight and ultimately obesity.

Overweight and obesity are risk factors for a number of chronic diseases, including cancer. To date, this forms a serious problem in adults, but even more so in children. Especially because it appears very difficult for an overweight or obese person to regain normal weight again. For obese kids this therefore implies that they will have a lifetime long increased risk for certain chronic diseases. This is already reflected in the occurrence at much younger ages of typical diseases like diabetes type 2, which are normally associated with elderly people. Finally, overweight and obesity will also reduce life expectancy.

The average daily composition of the diet will determine whether the intake of all essential nutrients (macro and micro) is adequate. If, for instance, the intake of vitamins and minerals is too low, this may result in deficiency diseases, some of which can be life-threatening. Current scientific insights however, demonstrate a more complex relationship between nutrition, diet and health, particularly for the chronic diseases (often called ‘lifestyle diseases’).

Not only an inadequate intake of vitamins and other micronutrients is unhealthy, also an excessive intake of specific macronutrients, such as the trans and saturated fatty acids, is known to have adverse effects on health.

Conversely, beneficial effects have been ascribed to certain non-nutrients, which are said to protect against some chronic illnesses, including several forms of cancer. This holds in particular for food constituents like fibre and certain secondary plant metabolites (such as polyphenols and lignans), found in fruit and vegetables.

Physical activity: role and determinants

Of course, the quantitative aspect of nutrition (amount of energy intake) is not the single determinant of weight gain. What really matters is the balance between energy intake and expenditure (energy balance).

Physical activity is the major determinant at the expenditure side of the energy balance. It can prevent weight gain at all ages, thereby decreasing the health risks of being overweight or obese. Regarding the (sub)determinants of physical activity itself we must again realize that it is the result, just like nutrition, of ‘supply’ on the one side , and ‘behaviour’ on the other side.

Due to urbanisation and industrialisation, the overall levels of physical activity have declined over the past century, in particular (but not exclusively) in high-income countries. These changes, moreover, seem to correlate with the changes observed in cancer patterns in these countries. This suggests again that cancer is a partly preventable disease.

The supply side concerns the possibilities and challenges to become physically active as determined by local infrastructure, employers, labour type and environment, access to cars and motorcycles, PC use, TV use etc. But, it is also influenced by the opportunities offered by schools, sports clubs etc. On the behaviour side, government promotion, social environment and personal determinants are likely to play an important role.

20 May 2008

Food, Nutrition, Physical Activity and Cancer

Which factors increase or decrease the risk of cancer

Dietary composition

Overweight and obesity

Growth and development, including lactation

Dietary composition

In the WCRF/AICR report (2007), the currently available evidence is reviewed for 17 cancer sites. Together, these sites amount to roughly 80 percent of the incidence of, and deaths from, all cancers worldwide. The selection and sequence of the sites, as presented in the following tables, is roughly in line with the body’s systems, or with sites that have anatomical, metabolic, hormonal, or other features in common.

According to the WCRF/AICR report (2007) the causal relationship between food, nutrition, physical activity, body composition, and cancer is and always will be incomplete. New methods of research, and new issues to study, are always being developed. However, the WCRF/AICR report (2007) distinguishes between five different 'grades' of evidence: 'convincing', 'probable', 'limited-suggestive', 'limited-no conclusion', and 'substantial effect on risk unlikely'. This EUphocus mainly focuses on the 'probable' and 'convincing' evidence of a causal relationship, either positive or negative. This because judgements of convincing or probable causal effects generally justify goals and recommendations (also see next chapter) for both prevention and futher research. The exact criteria used for judging whether evidence should be considered 'convincing' or 'probable' can be found in the WCRF/AICR report (chapter 3).

Increased cancer risk: convincing evidence

There is convincing evidence for an increased cancer risk by certain foods, drinks or food constituents in 6 of the 17 reviewed cancer sites, as shown in the next table. Four cancer sites concern the consumption of alcoholic drinks, while two others relate to specific carcinogenic contaminants in either drinking water or foods. The risk of lung and colorectal cancer, is also increased by the consumption of respectively a specific supplement or type of food (beta-carotene and red meat and processed meat).

Increased cancer risk: probable evidence

For oesophagus cancer there is probably an increased cancer risk by drinking an exotic hot drink (maté). Alcoholic drinks are probably increasing the risk for liver cancer (both men and women) and for colorectal cancer (only women).

Furthermore, a probable cancer risk is found in four additional cancer sites (nasopharynx, stomach, prostate and skin) by the intake of resp. salted fish, salted & salty foods, high calcium, and arsenic in drinking water.

Finally, for 7 cancer sites (pancreas, gallbladder, ovary, endometrium, cervix, kidney, bladder), the available experimental evidence indicate neither a convincing nor a probable increased cancer risk by foods, drinks or food constituents.

Decreased cancer risk: convincing evidence

For none of the reported 17 cancer sites in the WCRF/AICR report (2007) there is convincing evidence of a protective effect on cancer risk by any food, drink or food constituent.

Decreased cancer risk: probable evidence

The available evidence for a protective effect on cancer risk by certain foods, drinks and food constituents, is at best judged as ‘probable’. In total, this judgement is made for 7 of the 17 cancer sites. Four of these (lung, oesophagus, stomach, and mouth) concern the probable protective effects of non-starchy vegetables, fruits, foods with carotenoids and allium vegetables. The other three cancer sites concern the probable protective effect of foods containing folic acid (pancreas), dietary fibre, garlic, milk or calcium (colon and rectum), and lycopene or selenium (prostate).

Convincing increased cancer risks by foods, drinks or food constituents

Cancer site	Exposure
Mouth, pharynx, larynx	Alcoholic drinks
Nasopharynx	*
Oesophagus	Alcoholic drinks
Lung	- Beta-carotene suppl. ^a - Arsenic in drinking water
Stomach	*
Pancreas	*
Gallbladder	*
Liver	Aflatoxins ^b
Colorectum	- Red meat ^c ^- Processed meat ^c - Alcoholic drinks (men)
Breast: pre- and postmenopause	- Alcoholic drinks
Ovary	*
Endometrium	*
Cervix	*
Prostate	*
Kidney	*
Bladder	*
Skin	*

* Available evidence not considered to be convincing

a Concerns high dose supplements in smokers

b On contaminated foods (cereals, grains, legumes, seeds, nuts, some vegetables and fruits)

c Red meat refers to beef, pork, lamb and goat; proces-sed meat refers to: smoking,curing, salting, and addition of chemical preservatives

Overweight and obesity

Overweight and obesity are the result of continuous weight gain, due to a positive energy balance (energy intake in excess of energy expenditure). The excess energy from food and drinks is stored as fat in the body in adipose tissue.

Storage of fat in the body can be underneath the skin in upper arms, buttocks, belly, hips and thighs (subcutaneous storage). But it can also be stored intra-abdominally or viscerally (around the organs). Also a distinction is often made between ‘peripheral’ and ‘abdominal’ fat, i.e. between fat outside the trunk and fat that is more centrally located. The fat storage pattern is determined largely by genetic factors and also differs between the sexes. In women there is a tendency to store fat subcutaneously around hips, buttocks and thighs, while men are more likely to accumulate abdominal fat.

As indicator for total body fatness the ‘body mass index’ (BMI) is used with its specific defined cut-off points. For excess abdominal fat the waist circumference is a useful single indicator, also with its specific cut-off points.

Modifiers of weight gain, overweight and obesity

Factors that modify the occurrence of weight gain and its resulting overweight or obesity have also been studied. In conclusion, there is convincing evidence that physical activity reduces the risk of weight gain etc., while sedentary living increases it.

In addition, having been breastfed and intake of low energy-dense foods, will probably reduce the risk of weight gain and becoming overweight/obese. Consuming energy-dense foods, sugary drinks, fast foods or sedentary lifestyle (e.g. watching TV), will probably increase this risk.

Physical activity

The effect of physical activity itself on cancer risk, besides being protective towards weight gain, overweight and obesity, was investigated as well. Consistent and convincing evidence demonstrates that physical activity of all types protects against colon cancer. It probably also protects against female hormone-related cancers like endometrium and breast cancer (postmenopause).

These results are independent of other factors such as body fatness. Nevertheless, they seem to be well in line with the results of the paragraph on overweight and obesity.

Increased cancer risk: convincing evidence

The findings of the systematic literature reviews reported in the WCRF/AICR report (2007), indicate that there is convincing evidence that (excess) body fat increases the risk for the following six cancer sites.

Convincing evidence of increased cancer risk by body fatness and fat distribution

Cancer site	Exposure
Oesophagus ^a	Body fatness
Pancreas	Body fatness
Colorectum	- Body fatness - Abdominal fatness
Breast (postmenopause)	Body fatness
Endometrium	Body fatness
Kidney	Body fatness

a Adenocarcinoma only

Increased cancer risk: probable evidence

In addition, there is probably an increased risk for additional cancer types by body fatness (gall bladder), abdominal fatness (pancreas, breast [postmenopause], endometrium) and adult weight gain (postmenopausal breast cancer).

Decreased cancer risk

No convincing evidence was found for a decreasing effect on cancer risk by overweight and obesity in any of the 17 cancer sites studied. However, body fatness was found to be probably protective against premenopausal breast cancer.

Growth and development, including lactation

The size and shape of the human body, and the rate at which growth take place from conception to adult life, is determined by a strong interaction between genetic and environmental factors, among which nutritional factors.

Relevant body parameters studied in relation to cancer risk are birthweight, child growth, adult attained height, and lactation. Lactation is the process by which mothers produce their milk for breastfeeding. All these parameters are unlikely to directly modify the cancer risk. They do serve however as a marker for other genetic, environmental and nutritional factors which affect growth and development.

Increased cancer risk: convincing evidence

There is strong, consistent and convincing evidence that the risk of cancer at two sites is increased by the factors that lead to greater adult attained height. However, the nature of these factors, as well as the role played by nutrition, is still unclear.

Increased cancer risk: probable evidence

Furthermore, adult attained height probably also increases the cancer risk in several other sites: ovary, pancreas, breast (premenopause). In addition, the risk of premenopause breast cancer is probably increased by greater birthweight as well.

Decreased cancer risk: convincing evidence

It has been convincingly shown that women who breastfeed their child have a reduced risk of breast cancer at all ages thereafter (both premenopause and postmenopause).

Lactation is likely to influence the lifetime exposure to menstrual cycles, and thereby hormone levels which may influence cancer risk.

Convincing evidence of increased cancer risk by growth and development

Cancer site	Exposure
Colorectum	Adult attained height
Breast (postmenopause)	Adult attained height

Convincing evidence of decreased cancer risk by breastfeeding

Cancer site

Exposure

Breast (premenopause)

Breast (postmenopause)

- lactation

20 May 2008

Food, Nutrition, Physical Activity and Cancer

Latest developments and insights

Differences in judgement

Changed cancer risks and new insights

Differences in judgement

Between the first and second WCRF/AICR report (2007) there is a significant difference in the criteria for the judgement of the evidence.

In general, the criteria for weighting the strength of the evidence in the 2007 report, are more stringent than those of the first report. This holds especially for the judgement of a ‘convincing causal’ association. Supportive evidence from at least two independent cohort studies and plausible biological mechanisms were, among others, now considered mandatory for this. Besides these prospective studies, more emphasis was also put on well performed randomized clinical trials (RCT).

Due to the more stringent criteria, several protective effects that were considered to be ‘convincing’ in the first WCRF/AICR report, have been downgraded to ‘probable’. This holds in particular for fruits and vegetables (dietary composition). But upgrading of a few protective effects is also observed. In addition, the total evidence for increased cancer risks by overweight and obesity has become much stronger. Furthermore, some new cancer risks or protective effects were also noted.

Changed cancer risks and new insights

Food and nutrition

New findings concern the ‘probable’ protective effect of garlic, milk or calcium for colon/rectum cancer, and of lycopene and selenium for prostate cancer.

The evidence for cancer protection by fruits and vegetables is downgraded to ‘probable’ for mouth/pharynx, oesophagus, lung, and stomach. For cancer of the bladder, cervix and colon/rectum it has been ranked even lower. An upgrade of the cancer protective effects to ‘probable’ was observed for vitamin C (oesophagus) and for allium vegetables (stomach).

However, the evidence for an increased cancer risk by red (and processed) meat for colon and rectum was strengthened, and the same holds for the aflatoxins and liver cancer. New is the ‘probable’ carcinogenic risk of arsenic in drinking water (skin cancer) and the higher risk of prostate cancer due to high calcium intake.

Physical activity

Evidence of the protection by physical activity has become consistent and ‘convincing’ for colon cancer (independent of overweight). New are the ‘probable’ protective effects of physical activity against cancer of the endometrium and breast (postmenopause).

Overweight and obesity

The evidence for an increased cancer risk by body fatness and abdominal fatness has become stronger for oesophagus, pancreas (new), colon/rectum, breast (postmenopause), kidney, endometrium and gallbladder. But, body fatness probably protects against premenopausal breast cancer, although the mechanism is largely unknown.

Growth and development

The available data for the cancer protective effect of lactation has been upgraded to ‘convincing’ evidence. The ‘probable’ increased cancer risk by adult attained height for pancreas and ovary is a new finding.

20 May 2008

Food, Nutrition, Physical Activity and Cancer

Recommendations

General

Based on the data and evidence presented in its 2007 report, the WCRF/AICR have drawn up a set of 10 recommendations, eight more general and two special ones. For each of this set of 10 also public health goals and personal recommendations were derived. The public health goals are meant for populations, and thus in principal for health professionals, as a basis for developing health policies. Personal recommendations are meant to guide people, either as communities, families or individuals. All recommendations aim to integrate and to contribute to healthy dietary patterns, a healthy lifestyle and general well-being.

Recommendations

A summary of all recommendations is shown in the table below and in its original form also at the appropriate WCRF pages which do contain the full text.

1. Body fatness : Be as lean as possible within the normal range of bodyweight

Public	Median adult BMI between 21 and 23. Percentage overweight persons not to increase, and preferably lower in 10 years
Personal	Bodyweight gain at childhood and adolescence to give normal BMI at age 21.Maintain normal range BMI after age 21.Avoid weight gain and increasing waist circumference during adulthood

2. Physical activity: Be physically active as part of everyday life

Public	% of sedentary people to halve every 10 years. Average physical activity levels (PALs) to be above 1.6
Personal	Be moderately physically active for at least 30 min every day. As fitness improves aim for 60 min moderate or 30 min vigorous activity/day. Limit sedentary habits as TV watching.

3. Foods and drinks that promote weight gain: Limit consumption of energy-dense foods. Avoid sugary drinks

Public	Average energy density of diets to be lowered to 125 kcal/100 g. Population average consumption of sugary drinks to be halved every 10 years
Personal	Eat energy-dense foods sparsely. Avoid sugary drinks. Eat ‘fast foods’ sparingly, if at all.

4. Plant foods: Eat mostly foods of plant origin

Public	Population average intake of non-starchy fruits and vegetables at least 600 g/day. Cereals (grains), and/or pulses (legumes) and other foods with dietary fibre, daily average at least 25 g/day
Personal	At least 5 portions/servings a day of ns-vegetables and fruits. Eat cereals (grains) and pulses (legumes) with every meal. Limit refined starchy foods. If starchy roots/tubers are consumed as staples, ensure intake of enough non starchy vegetables, fruits and pulses (legumes).

5. Animal foods: Limit intake of red meat and avoid processed meat

Public	Population average of red meat no more than 300 g /week, little if any processed.
Personal	People eating red meat to consume less than 500 g/week, little if any processed.

6. Alcoholic drinks: Limit alcoholic drinks

Public	Reduction % population drinking more than recommended limits by one third every 10 years.
Personal	Limit daily consumption to no more than 2 drinks (women) and 3 drinks (men)

7. Preservation, processing, preparation: Limit consumption of salt. Avoid mouldy cereals (grains) or pulses (legumes)

Public	Population average salt (all sources) < 5 g per day. % of people consuming > 6 g/day to be halved every 10 years. Minimise exposure to aflatoxins (from mouldy cereals and pulses).
Personal	Avoid salt-preserved, salted, or salty foods. Limit intake of processed foods with added salt to < 6 g/day. Do not eat mouldy cereals or pulses.

8. Dietary supplements: Aim to meet nutritional needs through diet alone

Public	Maximize proportion of population achieving nutritional adequacy without dietary supplements.
Personal	Dietary supplements are not recommended for cancer prevention.

9. Breastfeeding: Mothers to breastfeed; children to be breastfed

Public	Majority of mothers to breastfeed exclusively, for six months.
Personal	Aim to breastfeed infants exclusively up to six months, continue with complementary feeding thereafter

10. Cancer survivors: Follow the recommendations for cancer prevention

Distinction not made by WCRF/AICR

All cancer survivors to receive nutritional care from an appropriately trained professional. Aim to follow the recommendations for diet, healthy weight and physical activity, unless otherwise advised or unable to do so.

20 May 2008

Food, Nutrition, Physical Activity and Cancer

Related EUphacts and EUphoci

Alcohol policies

Alcohol use

Alcohol-related deaths

Ischaemic heart disease

Overweight