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Nutrition and Performance in Sport

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Christophe Hausswirth

Chapter 2. Nutrition, sport and health

Topic 1. Food, physical activity and health: from research to recommendations

Serge Hercberg

Résumé

In the field of nutrition, France and most industrialized countries are face with major public health challenges. Of course, the difference between dietary intake and the body’s real requirements cannot be considered a direct cause of the large majority of chronic diseases. However, the diet, physical activity and the resulting nutritional status determine, directly and indirectly, the health status of populations. Chronic diseases linked to nutrition (cancers, cardiovascular diseases, osteoporosis, obesity, type 2 diabetes, etc.) have a significant impact in terms of public health, at human, social and economic levels.
These chronic diseases are described as multifactorial, since biological, physiological and genetic, as well as many environmental factors, contribute to their onset, development or clinical expression. Among these factors, food and physical activity are now considered to be major contributors which can be modulated through public health interventions to promote prevention.
Over the past 30 years, many scientific studies – performed on cell models, organs, animals, patients or healthy people, as well as in wider populations – showed, with different degrees of certainty, that nutritional factors (excess or deficiency) contribute to many chronic diseases. These studies not only concern food in general, but also identify precise food groups, – and micronutrients and non-nutrients – as well as physical activity. Even though, in many cases the evidence available does not (yet) allow us to confirm the link between the suspect nutritional factor and some diseases, in other cases the convergence of the evidence has led to an international consensus and recommendations.
Given the nutrition-related public health stakes, and taking into account the opinion of many scientific experts, with the support of all the ministries and institutions concerned, the French Ministry of Health implemented, the French Nutrition and Health Programme (PNNS) in 2001. The general objective of this programme is to enhance the population’s health status by acting on the major contributing factor: nutrition.

Texte intégral

1. Introduction

1Nutrition, in its modern sense, includes dietary intake (which covers nutrients, food and eating behaviour, social, cultural, and economic determinants) and physical activity.

2Until recently, the relationship between nutrition and health was perceived through the clinical manifestations of nutritional deficiency diseases. The evidence for this relationship was based on the clinical pictures associated with starvation and significant food deficiencies or specific deficiencies which were historically observed. Thus, a lack of protein was found to be responsible for obvious clinical forms of kwashiorkor; a lack of energy intake was associated with marasmus; vitamin C deficiency was linked to scurvy; vitamin B1 deficiencies were associated with beriberi; etc.

3In recent decades, in France and other industrialized countries, a situation of food abundance has developed (except during the two World Wars), which has led to the disappearance of the majority of deficiency diseases which were still prevalent in Europe and North America at the beginning of the twentieth century. However, these diseases remain very common in developing countries. This situation has resulted in the most obvious aspects of the relationship between food and health being lost to view in industrialized countries, whereas they remain dramatically present in many parts of the world.

4The public health stakes resulting from the relationship between nutrition and health, which a country like France must face at the beginning of the twenty-first century, are of another kind. The imbalance between dietary intake and a lack of physical activity cannot, generally speaking, be considered to be a direct cause of the most common chronic diseases. And yet, food, physical activity and the resulting nutritional status directly and indirectly determine health status in these populations. Chronic diseases linked to nutrition (cancers, cardio-vascular diseases, osteoporosis, obesity, type 2 diabetes, etc.) have a significant impact in terms of public health, at the human, social and economic levels.

5In 2005 alone, the French Institute for Public Health Surveillance (InVS, 2010a) estimated at 320000 the number of new cases of cancer (180000 in men and 140000 in women) in France. The most frequent localisations were: 62000 cases of prostate cancer, 50000 cases of breast cancer, 37500 cases of colorectal cancer and 31000 cases of lung cancer. Since 2004, cancers have become the main cause of death, despite the decreased risk of mortality due to the development of early diagnosis methods and more efficient treatments. Cancer is the leading cause of death in men (one death in three), and the second leading cause of death in women (one death in four). In 2005, the number of people who died of cancer in France was estimated at 146000.

6Cardiovascular diseases are responsible for about 180000 deaths per year (i.e. 32% of deaths), with 25% of these deaths are in under-75-year-olds. The most frequent cardiovascular diseases are ischaemic heart disease (27% of deaths), strokes (25% of deaths) and heart failure (23% of deaths). These three groups of diseases account for 75% of deaths related to cardiovascular diseases. The prevalence of cardiovascular diseases is difficult to assess, but the annual number of myocardial infarctions is estimated at 120000, whereas that of strokes is estimated at 130000.

7The prevalence of pharmacologically treated diabetes in France was estimated by the Social Security system at 3.95% in 2007. This corresponded to 2.5 million patients treated for diabetes, of which 600000 are treated with insulin. A peak of prevalence is observed between the ages of 75 and 79, with 18% of men and 13% of women in this age group treated for diabetes (InVS, 2010b). Obesity affects 17% of adults and 3 to 4% of children in France (Castetbon et al. 2009), while osteoporosis affects 10% of 50-year-old women, 20% of women aged 60, and 40% of women over 75 years of age.

8In addition to their consequences for the patients themselves, these diseases have a significant economic impact, with the direct and indirect costs of cancers estimated at eight billion euro per year, while those related to cardiovascular diseases are estimated at five billion euro per year, and obesity-related costs come in at two billion euro per year.

9These chronic diseases are known as multifactorial diseases since biological, physiological and genetic causes, as well as many environmental factors contribute to their onset, development or clinical expression. Among the environmental factors involved, food and physical activity are now considered to be major contributors.

10Even though it is not easy to precisely measure the relative impact of nutritional factors in determining diseases, several sources of evidence suggest that it is high. Thus, in the case of cancers, an analysis performed by Doll and Peto (1981) in the early 1980s showed that food contributed to between 30 and 40% of cancers in men and 60% in women. More recently, the World Cancer Research Fund published a report (Table 1) listing the proportion of cancers associated with nutrition. The values in this report range from 27 to 34% depending on the country considered (WCRF/AICR, 2007).

Table 1: How nutrition contributes to the most common cancers in different countries.

Table 1: How nutrition contributes to the most common cancers in different countries.

11Of course, the way this estimation was calculated can be contested, but these figures reveal the significant role of food factors in determining the occurrence of chronic diseases. As food or physical activity are easily adjustable phenomena, this observation is very interesting in terms of public health and prevention.

12As an example of the effect intervention could have, let us discuss the expected effects of reducing sodium consumption in the United States. Bibbins-Domingo et al. (2010) indicate that reducing the average salt intake by 3 g (1200 mg of sodium) in the American population would lead to an annual reduction in the number of heart disease cases by 60000 to 120000, of strokes by 32000 to 66000, and of myocardial infarctions by 54000 to 99000. This would result in a 10-to 24-billion-dollar reduction in the yearly healthcare budget.

13Similarly, the costs related to physical inactivity in the United States are estimated at more than 24 billion dollars a year.

14Given the public health impact of nutrition, it seems necessary to identify risk or protective factors associated with nutrition that are based on solid scientific evidence with an adequate level of proof.

2. From scientific evidence to public health recommendations

15If we take the example of the nutrition–cancer field, a collective international assessment was performed by the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR). The report of this assessment (WCRF/AICR, 2007) was based on systematic reviews and hundreds of meta-analyses performed by nine international centres extracted from a corpus of 7000 original scientific articles published before 2006 and identified as relevant. All these reviews and meta-analyses were discussed and independently assessed by a panel of 21 international experts.

16The level of proof was qualified taking into account the different types of study (case-control studies, cohort studies, randomized controlled trials, mechanistic studies), the amount, quality and nature of the data, the absence of heterogeneity and the biological plausibility:

17■ convincing level of proof:

  • provided by at least two types of study and two independent cohort studies;

18■ plausible level of proof:

  • provided by at least two independent cohort studies or at least five case-control studies.

19The qualifiers “limited/suggestive” and “limited and not convincing” were awarded to lower levels of proof.

20Only “convincing” and “plausible” data were used to formulate recommendations for individuals and to promote public health objectives.

21Similar collective assessments have been performed in the field of the nutritional determinants related to various chronic diseases (cardiovascular diseases, diabetes, osteoporosis, etc.).

22Based on these collective analyses, performed with strict methodological rigour, nutritional recommendations have been established and serve as the basis for public health recommendations. In France these recommendations are published by the PNNS. Given the public health stakes linked to nutrition, and taking into account the opinion of many scientific experts, in 2001 the French Ministry of Health, with the support of all the ministries and institutions concerned, implemented the French Nutrition and Health Programme (PNNS). The general objective of this programme is to enhance the population’s health status by acting on the major contributing factor: nutrition.

23The 2001-2005 and 2006-2010 PNNS provided a coherent reference framework and allowed various tools to be developed to serve as a basis for a number of complementary synergistic actions. These actions are based on the mobilization of numerous interested parties (health, physical activity, education, and social-work professionals, local politicians, economic players, associations, etc.).

24PNNS 3 was launched for the 2011-2015 period based on four main lines:

Line 1 Through specific general prevention actions, to reduce the health-related social differences in the field of nutrition

Line 2 To develop physical and sports activity and limit sedentary lifestyles.

Line 3 To organize detection and care for patients based on their nutrition.

Line 4 To promote the PNNS as the reference for nutrition actions.

25Line 2 of PNNS 3 thus focuses on physical and sporting activities. Indeed, in a society where movement is increasingly reduced, the “moving” component of nutrition represented by physical activity was shown to be essential to the energy balance, at all stages of life. Many initiatives have been developed to encourage the adoption of the PNNS indicator “at least 30 minutes of physical activity per day”. However, the French Authority on Public Health (HCSP) deemed it necessary to reinforce the actions, taking into account the objectives fixed in this field.

26A new dimension was thus given to physical activity in the 2011-2015 PNNS. Physical activity is a vector of social and educational values and has a beneficial effect on health, whether it is practised during daily activities or in the setting of a sports club. It is also an adjuvant therapy for patients receiving treatment.

27Two levels of physical and sports activity will be developed:

  • daily physical activity, during transport time, leisure and work, associated with regular supervised physical activity;

  • adapted physical activity within the framework of a healthcare programme for people with chronic diseases.

Bibliographie

3. Bibliographic references

Bibbins-Domingo K, Chertow GM, Coxson PG, Moran A, Lightwood JM, Pletcher MJ, Goldman L. 2010. “Projected effect of dietary salt reductions on future cardiovascular disease.” In N Engl J Med. 362(7):590-9.

Castetbon K, Vernay M, Malon A et al. 2009. “Dietary intake, physical activity and nutritional status in adults: the French nutrition and health survey.” (ENNS, 2006-2007). In Br J Nutr. 102(5):733-743.

Doll R, Peto R. 1981. “The causes of cancer: quantitative estimates of avoidable risks of cancer in the United States today.” In J Natl Cancer Inst. 66(6):1191-1308.

Institut de veille sanitaire. “Estimations d’incidence et de mortalité par cancer en France entre 1980 et 2005.” In http://www.invs.sante.fr/publications/2009/estimation_cancer_1980_2005/estimation_cancer_1980_2005.pdf.

Institut de veille sanitaire. “Prévalence et incidence du diabète.” In http://www.invs.sante.fr/publications/2010/plaquette_diabete/plaquette_diabete.pdf Ministère des affaires sociales et de la santé. “Programme national nutrition santé 2011-2015.” In http://www.sante.gouv.fr/IMG/pdf/PNNS_2011-2015.pdf.

World Cancer Research Fund (WCRF)/American Institute for Cancer Resaerch (AICR). 2007. “Food, nutrition, physical activity, and the prevention of cancer: a global perspective.” In http://www.dietandcancerreport.org/cancer_resource_center/downloads/Second_Expert_Report_full.pdf.

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