1 INTRODUCTION Adolescents are tomorrow's adult population and their health and well-being are crucial.Yet.interest in adolescents'health is relatively recent and a focus on nutrition is even more recent,with the exception of adolescent pregnancy.This discussion paper intends to make evidence-based recommendations directed at the health sector to improve the contribution of health-care providers to nutritional health of adolescents,particularly in developing countries. 1.1 Adolescents:Who are they? The term youth encompasses ages 10 to 24 years,while the term adolescents as defined by WHO(1986a) includes persons aged 10-19.Adolescents are sometimes designated as'children,for instance,in the UN Convention on the Rights of the Child of 1989,which applies to all individuals below 18 years of age. The period of gradual transition from childhood to adulthood that normally begins with the onset of signs of puberty,is characterized by important psychological and social changes,not only physiological change.It is difficult to define in universal terms for there are important cultural differences.Depending on societies,the transition may be quick and the very notion of adolescence does not really exist,for instance where girls marry early and do not go to school.On the other hand,the transition of adolescence may extend over several years where young people remain in school and marry late,like in developed countries and increasingly in urban areas of developing countries(Paxman and Zuckerman,1987). Adolescents are far from being a homogeneous group,in terms of development,maturity and lifestyle. Even for a given place and age,there is a great deal of diversity depending on personal and environmental factors.Adolescence may be divided into three developmental stages based on physical,psychological and social changes(WHO/UNICEF 1995): Early adolescence,10/13-14/15 years; Mid adolescence,14/15-17; Late adolescence,between 17-21,but variable. Being in transition,adolescents may no longer benefit from the attention and care that usually go to children,but they may not get the protections associated with adulthood either. Adolescents make up roughly 20%of the total world population.In developing countries,adolescents have an even higher demographic weight,for instance,roughly 26%in Salvador,compared to 14%in USA(Burt 1996).Similarly,in the Philippines,it is estimated that adolescents represent one quarter of the total population(Bouis et al,1998).In 1995,there were914 million adolescents living in the developing world,that is,85%of the total(United Nations 1997).Their number is expected to reach 1.13 billion by the year 2025.With a lower fertility decline,Africa is expected to see its adolescent population grow much more rapidly than Asia and Latin America. Adolescence is a period of rapid growth:up to 45%of skeletal growth takes place and 15 to 25%of adult height is achieved during adolescence(Rees and Christine,1989).During the growth spurt of adolescence, up to 37%of total bone mass may be accumulated(Key and Key,1994).Nutrition influences growth and development throughout infancy,childhood and adolescence;it is,however,during the period of adolescence that nutrient needs are the greatest(Lifshitz,Tarim and Smith,1993). Psychological and social aspects of adolescents'development are less often described in connection with adolescent health than their physical growth and maturation characteristics(Gillespie 1997).And yet NUTRITION IN A DO LESCE N CE /1NUTRITION IN ADOLESCENCE / 1 1 INTRODUCTION Adolescents are tomorrow’s adult population and their health and well-being are crucial. Yet, interest in adolescents’ health is relatively recent and a focus on nutrition is even more recent, with the exception of adolescent pregnancy. This discussion paper intends to make evidence-based recommendations directed at the health sector to improve the contribution of health-care providers to nutritional health of adolescents, particularly in developing countries. 1.1 Adolescents: Who are they? The term youth encompasses ages 10 to 24 years, while the term adolescents as defined by WHO (1986a) includes persons aged 10-19. Adolescents are sometimes designated as ‘children’, for instance, in the UN Convention on the Rights of the Child of 1989, which applies to all individuals below 18 years of age. The period of gradual transition from childhood to adulthood that normally begins with the onset of signs of puberty, is characterized by important psychological and social changes, not only physiological change. It is difficult to define in universal terms for there are important cultural differences. Depending on societies, the transition may be quick and the very notion of adolescence does not really exist, for instance where girls marry early and do not go to school. On the other hand, the transition of adolescence may extend over several years where young people remain in school and marry late, like in developed countries and increasingly in urban areas of developing countries (Paxman and Zuckerman, 1987). Adolescents are far from being a homogeneous group, in terms of development, maturity and lifestyle. Even for a given place and age, there is a great deal of diversity depending on personal and environmental factors. Adolescence may be divided into three developmental stages based on physical, psychological and social changes (WHO/UNICEF 1995): • Early adolescence, 10/13-14/15 years; • Mid adolescence, 14/15-17; • Late adolescence, between 17-21, but variable. Being in transition, adolescents may no longer benefit from the attention and care that usually go to children, but they may not get the protections associated with adulthood either. Adolescents make up roughly 20% of the total world population. In developing countries, adolescents have an even higher demographic weight, for instance, roughly 26% in Salvador, compared to 14% in USA (Burt 1996). Similarly, in the Philippines, it is estimated that adolescents represent one quarter of the total population (Bouis et al, 1998). In 1995, there were 914 million adolescents living in the developing world, that is, 85% of the total (United Nations 1997). Their number is expected to reach 1.13 billion by the year 2025. With a lower fertility decline, Africa is expected to see its adolescent population grow much more rapidly than Asia and Latin America. Adolescence is a period of rapid growth: up to 45% of skeletal growth takes place and 15 to 25% of adult height is achieved during adolescence (Rees and Christine, 1989). During the growth spurt of adolescence, up to 37% of total bone mass may be accumulated (Key and Key, 1994). Nutrition influences growth and development throughout infancy, childhood and adolescence; it is, however, during the period of adolescence that nutrient needs are the greatest (Lifshitz, Tarim and Smith, 1993). Psychological and social aspects of adolescents’ development are less often described in connection with adolescent health than their physical growth and maturation characteristics (Gillespie 1997). And yet