Avis d'experts sur les besoins en énergie et en éléments nutritifs
Asesoramiento de expertos sobre las necesidades de energía y nutrientes
An FAO tradition
Robert Weisell is a Nutrition Officer in the Nutrition Planning, Assessment and Evaluation Service, FAO Food and Nutrition Division. He is currently serving as Chief Technical Advisor for Development of a Regional Food Security and Nutrition Information System in Zimbabwe.
Knowledge of human nutrient requirements is essential for assessing whether food supplies are adequate to meet a population's nutritional needs. It helps governments to monitor nutrition programmes and plan development activities in general. In 1948, the Standing Advisory Committee to the newly formed Food and Agriculture Organization considered that "the problem of assessing the calorie and nutrient requirements of human beings, with the greatest possible degree of accuracy, is of basic importance to FAO" (FAO, 1950). The provision of this crucial information has been a function of the Food and Nutrition Division since FAO's founding five decades ago.
Under the auspices of FAO, scientific and technical recommendations are made by expert groups established by the FAO Conference and Council or at the discretion of the Director-General, comprising individuals who are appointed to serve in their personal capacity (FAO, 1994). When FAO and the World Health Organization (WHO) began their successful collaborative efforts in various nutrition activities in the 1950s, the FAO/WHO Expert Committee on Nutrition was formed to provide technical advice on a regular basis to the Directors-General of FAO and WHO. Other expert groups have been convened to deal with specific nutrition issues as they have arisen. During the past decade, two or three meetings of such groups have been held every year.
The primary purpose of expert meetings on nutrient requirements has remained the same: to advise the Directors-General on scientific issues related to calorie and nutrient requirements so that appropriate recommendations for action can be formulated. The various expert groups have contributed principles for determining and applying general requirements which have been adopted worldwide. The global scientific community has embraced the advice on requirements published first by FAO and later in collaboration with WHO. These "FAO/WHO recommendations" are utilized in virtually all countries. Not only have the FAO/WHO recommendations reflected the state of knowledge at particular points in time, but they have also influenced research agendas and methodologies over the years. The nutrition requirement reports rank among the best-selling and most sought-after publications of both FAO and WHO.
FAO EXPERT RECOMMENDATIONS ON ENERGY AND NUTRIENT REQUIREMENTS
Calorie requirements. Report of the Committee on Calorie Requirements. FAO Nutritional Studies No 5. 1950.
Calorie requirements Report of the Second Committee on Calorie Requirements. FAO Nutritional Studies No. 15. 1957.
Protein requirements. Report of the FAO Committee on Protein Requirements. FAO Nutritional Studies No, 16. 1957.
Calcium requirements. Report of an FAO/WHO Expert Group. FAO Nutrition Meetings Report Series No. 30. 1962.
Protein requirements. Report of a Joint FAO/WHO Expert Group. FAO Nutrition Meeting Report Series No 37/WHO Technical Report Series No. 301. 1964.
Requirements of vitamin A, thiamine, riboflavin and niacin. Report of a Joint FAO/WHO Expert Group. FAO Nutrition Meetings Report Series No. 41. 1967.
Requirements of ascorbic acid, vitamin D, vitamin B12, folate, and iron. Report of a Joint FAO/WHO Expert Group. FAO Nutrition Meeting Report Series No. 47. 1970.
Energy and protein requirements. Report of a Joint FAO/WHO Ad Hoc Expert Committee. FAO Food and Nutrition Series No. 7/FAO Nutrition Meetings Report Series No. 52/WHO Technical Report Series No. 522.1973.
Dietary fats and oils in human nutrition. A Joint FAO/WHO. Report FAO Food and Nutrition Paper No. 3. 1977.
Carbohydrates in human nutrition. A Joint FAO/WHO Report. FAO Food and Nutrition Paper No. 15. 1980.
Energy and protein requirements Report of a Joint FAO/WHO/UNU Expert Consultation. WHO Technical Report Series No. 724. 1985.
Requirements of vitamin A, iron, folate and vitamin B12. FAO Food and Nutrition Series No. 23. 1988.
Protein quality evaluation. Report of the Joint FAO/WHO Expert Consultation. FAO Food and Nutrition Paper No 51. 1991.
Trace elements in human nutrition. Report of a Joint FAO/WHO/IAEA Expert Consultation. WHO Technical Report Series. 1995 (in press).
Fats and oils in human nutrition. Report of a Joint Expert Consultation. FAO Food and Nutrition Paper No. 57. 1994.
ENERGY AND PROTEIN
While expert groups have been convened to cover a range of nutrition topics, the expert recommendations for energy and protein have received the most attention. The first of the meetings of experts in this area was held three years after FAO began operations. It was convened to address the issue of calorie needs. In the foreword to the report of this meeting (FAO, 1950), the first Director of the Nutrition Division, Wallace R. Aykroyd, observed that "even tentative recommendations would be of immediate practical value to FAO but also to its member countries". The recommendations would also be of value to "nutrition workers and others concerned with the problems of food requirements".
Many of the points made by the first committee on calorie requirements are still pertinent today. The requirements set by the experts were intended for groups of persons rather than individuals, and the committee established the principle, which is often misunderstood, that "an average requirement can never be compared directly with an individual (requirement)" (FAO, 1950). The first committee on calories offered the very practical rule of thumb that if the person "is in good health and calorie balance, that is, neither over - nor underweight, then he or she is consuming food according to his or her calorie requirements". Subsequent committees in addition recognized the importance of maintaining an adequate level of energy expenditure, thus acknowledging that recreational activities were important to the overall health status of many people and that energy requirements did not refer to a minimum level (FAO, 1965).
The first committee noted that its recommendations should be adjusted depending on how and for whom they are used, and it cautioned that nutrition and health experts within countries should take into account local conditions in applying the requirements. There is always the need to exercise judgement in interpreting and using requirement values, yet advice in this area is most difficult to impart to users. The first committee also pointed out that the recommended requirement values were determined at the physiological level, while the country's food supply was often estimated at the retail level; therefore, some amount of adjustment was required to assist in the assessment of calorie needs (FAO, 1950). The secretariat was assigned the mandate of preparing a chapter or section of the report addressing the practical applications of the requirements.
Later committees refined and revised these early basic concepts and introduced new ones. The committees also emphasized the important relationship between calories and other nutrients and stressed that sufficient calories should not necessarily be equated with adequate nutrition.
The first FAO committee convened to determine protein requirements met in 1955. There was a crucial difference between the methods that were appropriate for determining dietary requirements for protein and other nutrients, and those for calories. Whereas calorie requirements were presented as an average (whereby it was considered "normal" for half the homogeneous population to be below the mean and half above), requirements for protein and other nutrients were presented as the top end of the normal distribution of intakes or needs, a level termed "safe level of intake". Quantity of protein was not the only consideration; the quality aspect also demanded the attention of this and future expert groups.
By the 1960s, the scientific community began to recognize and stress the close link between energy and protein. It was increasingly realized that neither could be considered in isolation from the other; adequate protein intake in a low-calorie diet was not acceptable, and attention shifted to increasing energy consumption.
Because of this close relationship, the next expert groups on energy and protein met jointly in 1971 (FAO/WHO; 1971). This meeting and a subsequent informal small gathering in 1975 to review the subject revealed a number of glaring gaps, in knowledge, and research activities were initiated. For the first-time, FAO and WHO were promoting, guiding and sometimes sponsoring the research on nutrient requirements. One study, sponsored by the Danish International Development Agency (DANIDA), involved the energy and protein requirements of poor children and was conducted in Guatemala, Thailand and Jamaica.
The 1981 expert group meeting felt that, except for children, sufficient information was available to use energy expenditure to determine energy requirements. Use of the basal metabolic rate (BMR) became important in expressing energy requirements. The experts identified a new methodology for calculating energy requirements, and substantial research needed to be carried out after the expert consultation. An expert meeting on the practical application of energy requirements was held in 1987, and a manual for planners and nutritionists was written (James and Schofield, 1990).
PROTEIN RECEIVED PRIORITY
Beginning in the 1950s, it was commonly perceived that a major nutrition problem was a lack of sufficient-protein in the diets of young children. The First Joint FAO/WHO Expert Committee on Nutrition noted that "one of the most widespread nutritional disorders in tropical and sub-tropical areas is the syndrome at present ill-defined and known by various names such as kwashiorkor" (WHO, 1949). A global investigation was launched to assess the extent of protein malnutrition, with particular attention to young children.
Interest in protein-rich foods, supplements and preparations to alleviate protein deficiency was widespread. In the mid-1950s, the WHO/FAO/United Nations Children's Fund (UNICEF) Protein Advisory Group (PAG) was established to "act on behalf of the Director-General of WHO in rendering advice to FAO and UNICEF of the safety and suitability for human consumption of proposed new protein-rich food preparations" (Van Veen and Scott Van Veen, 1974). PAG recommendations had a significant influence on the food and nutrition programmes of FAO and other agencies until the mid-1970s. By this point, research and interventions stressed the importance of meeting energy needs and re-emphasized the need to consider the combination of protein and energy rather than protein alone.
The human requirements for micronutrients have been the subject of expert group meetings as well. Calcium was reviewed in 1961, and later ascorbic acid, vitamin D, vitamin B12, folate and iron were the topics of meetings. Vitamin A, iron, folate and vitamin B12 were reviewed again in 1985, the first two because they were major nutritional public health problems and the latter two because of their close association with anaemia.
WHO convened the first Expert Group on Trace Elements in 1973 (WHO, 1973). By 1990, additional information regarding the role and importance of many trace elements had come to light, and an FAO/WHO expert group that year made a special effort to insure a reasonable degree of uniformity in the analysis and presentation of the many nutrients considered. Perhaps the most significant and yet confounding conclusion from the 1990 expert group was the realization that trace element requirements can change according to the type and amount of food consumed, interrelationships with other nutrients and the nutritional status of the individual (Weisell, 1991).
Two expert groups have met to discuss dietary fats and oils, one in 1977 and the other in 1993. These groups found it necessary to develop recommendations for poorer populations whose diets may lack sufficient fat, as well as for affluent populations which may have health concerns related to excessive consumption of fat.
When FAO began operations 50 years ago, there was comparatively little information on nutrient requirements and there were only a few experts in the field. The first expert group acknowledged that its recommendations were provisional because knowledge is in a continuous state of flux. Particularly in the early years, the limited information on requirements came from developed regions of the world and mostly from the laboratory setting. These limitations did not deter the early committees but did instill a certain degree of caution. It is a tribute to the early secretariat and the first expert groups that the basic premises they set remain today.
It is still true that scientists do not have all the information they desire, and this must be kept in mind. Conversely, there is now a problem of wealth of information, and more time and resources are needed to assess the scientific evidence. Nutritional science has grown more complex, each nutrient is studied by many scientists and there are more competing views. When experts come together for a meeting, they sometimes have difficulty arriving at definitive conclusions concerning complicated and specialized topics.
From the start, most expert groups have sought to address the practical application of the requirements. Time and events have shown that this aspect is as complex as determining the requirements themselves. Whatever the difficulties incurred in determining the recommendations, the scientific community and member countries still look to the expert groups to provide the definitive pronouncements on nutrient requirements and their use. The effort to provide information of high scientific quality which meets diverse needs throughout the world will continue.
FAO. 1950. Calorie requirements. Report of the Committee on Calorie Requirements, Washington, DC, 12-16 December 1949. FAO Nutritional Studies No. 5. Washington, DC.
FAO. 1965. Protein requirements. Report of a joint FAO/WHO Expert Group. FAO Nutrition Meetings Report Series No. 37. Rome.
FAO. 1994. Constitution. Basic texts of the Food and Agriculture Organization of the United Nations. 1994 edition. Rome.
FAO/WHO. 1971. Experiences in the application of the recommendations of the report of the second FAO Committee on Calorie Requirements (1957) and report of a Joint FAO/WHO Expert Group on Protein Requirements (1965). FAO/WHO Ad Hoc Committee of Experts on Energy and Proteins, Requirements and Recommended Intakes, Rome, 22 March - 2 April 1971. Rome.
James, W.P.T. & Schofield, E.C. 1990. Human energy requirements. A manual for planners and nutritionists. Oxford, UK, Oxford University Press/FAO.
Van Veen, A.G. & Scott Van Veen, M.L. 1974. Pioneer work in protein foods. Nutr. Newsl., 11(4): 22-25.
Weisell, R.C. 1991. Trace elements in human nutrition. Food, Nutr. Agric., 1(2/3): 25-29.
WHO. 1949. Report of the First Joint FAO/WHO Expert Committee on Nutrition. Geneva, 24-28 October. Geneva.
WHO. 1973. Trace elements in human nutrition: report of a WHO Expert Committee. WHO Technical Report Series No. 532. Geneva.
Depuis 1948, l'Organisation des Nations Unies pour l'alimentation et l'agriculture (FAO) fournit des renseignements sur les besoins humains en éléments nutritifs, qui sont essentiels pour l'évaluation et la surveillance des situations alimentaires et l'élaboration des programmes nutritionnels. La FAO finance des réunions scientifiques et techniques dans le cadre desquelles les experts fournissent au Directeur général des avis qui servent de base à l'élaboration des recommandations d'action appropriées. Au fil des ans, ses recommandations ainsi que celles qu'elle fait conjointement avec l'OMS traduisent l'état des connaissances nutritionnelles tout en influant sur la recherche a mener. Ces recommandations sur les besoins en éléments nutritifs sont suivies dans le monde entier.
La FAO a mis sur pied une série de groupes d'experts quand, en 1949 elle convoqua le premier Groupe d'experts sur les besoins énergétiques. Les divers groupes (énergie et protéine, matières grasses, oligo-éléments) ont mis au point un ensemble de principes pour la détermination et l'application de prescriptions générales, qui ont été adoptés à l'échelle mondiale. Ils ont, cependant, fait une mise en garde: les recommandations demandent à être modulées en fonction des modalités d'application et des groupes visés, la mise en oeuvre des prescriptions devant dûment tenir compte des conditions locales.
A l'origine, il n'y avait pas pléthore d'experts en nutrition ni foisonnement d'informations, lesquelles provenaient surtout de pays développés et d'expériences menées en laboratoire. De nos jours, la science nutritionnelle est devenue plus complexe; la profusion d'informations exige plus de temps et de ressources pour évaluer les faits scientifiques. La plupart des groupes d'experts se sont en outre penchés sur l'utilisation pratique des données relatives aux besoins humains. Or le temps et l'expérience montrent que cette dimension est aussi difficile a appréhender que la détermination des besoins eux-mêmes. La communauté scientifique et les Etats Membres attendent des groupes d'experts des avis précis sur les besoins en éléments nutritifs et sur l'utilisation des données. Offrir des informations de qualité scientifique qui répondent à la demande exprimée par des groupes d'utilisateurs très divers de par le monde continuera d'être un volet important des activités de la FAO dans les années qui viennent.
Desde 1948, la FAO ha facilitado información sobre las necesidades humanas de nutrientes, indispensable para la evaluación y supervisión de las situaciones alimentarias y para la planificación de programas nutricionales. La FAO patrocina reuniones científicas y técnicas en las que los expertos prestan asesoramiento al Director General de la Organización para que se puedan formular recomendaciones apropiadas sobre posibles acciones. Las recomendaciones de la FAO y de la FAO/OMS han reflejado siempre los conocimientos actuales sobre nutrición y, a la vez, han ejercido una influencia sobre las nuevas investigaciones. Las recomendaciones de la FAO y de la FAO/OMS sobre las necesidades de nutrientes han sido adoptadas por la comunidad científica mundial y dichos datos sobre necesidades de nutrientes se utilizan en todo el mundo.
La FAO comenzó sus reuniones de expertos en 1949 convocando a un grupo de expertos sobre las necesidades calóricas. Gracias a estos grupos (por ejemplo, sobre energía y proteínas, grasas y aceites, oligoelementos) se ha logrado un conjunto de principios útiles para determinar y aplicar las necesidades generales que se han adoptado en todo el mundo. Al mismo tiempo, han advertido que algunas recomendaciones debían reajustarse, según cómo y para quién se utilizaban, y que se debían tener en cuenta las condiciones locales al aplicar los datos sobre necesidades.
Cuando comenzó la FAO, había pocos expertos en nutrición y comparativamente poca información, la mayor parte proveniente de los países desarrollados y de experimentos de laboratorio. Actualmente, la ciencia nutricional se ha vuelto más compleja; con el cúmulo actual de información se necesita más tiempo y mayor cantidad de recursos para evaluar las pruebas científicas. Además, la mayoría de los grupos de expertos ha tratado de abordar las aplicaciones prácticas de las necesidades. El tiempo y los hechos han demostrado que este aspecto es tan díficil como la determinación misma de las necesidades. La comunidad científica y los Estados Miembros se apoyan en los grupos de expertos para hacer los pronunciamientos definitivos sobre las necesidades de nutrientes y su utilización, suponiendo que la información de alta calidad científica que satisface las necesidades de muchas partes del mundo continuará siendo un aspecto importante de la labor de la FAO en el futuro.