Public health nutrition is given more emphasis than clinical nutrition since promotion and prevention are deemed more critical to adolescent nutritional health than individual case management and because the recommendations are primarily intended for health-care providers and not for clinical nutritionists or dietitians This paper does not discuss in detail nutritional requirements and dietary allowances of adolescents, nor does it delve into specific clinical conditions requiring therapeutic diets.It is felt that these aspects are beyond the scope of the present study.Furthermore,it was impossible to cover in this already broad study all nutritional disorders,deficiencies and risks in an exhaustive manner,and therefore only those that appear of higher priority are considered. Following a presentation of nutritional opportunities,problems and risk factors in adolescence,general strategies and approaches are reviewed.More specific actions for the health sector to address nutrition- related needs of adolescents are then discussed in the light of scientific evidence and lessons learned, while insisting on the importance of intersectoral approaches to nutrition in consideration of the multifactorial aetiology of nutrition problems. NUTRITION IN A DO LESC E N CE /5
NUTRITION IN ADOLESCENCE / 5 Public health nutrition is given more emphasis than clinical nutrition since promotion and prevention are deemed more critical to adolescent nutritional health than individual case management and because the recommendations are primarily intended for health-care providers and not for clinical nutritionists or dietitians. This paper does not discuss in detail nutritional requirements and dietary allowances of adolescents, nor does it delve into specific clinical conditions requiring therapeutic diets. It is felt that these aspects are beyond the scope of the present study. Furthermore, it was impossible to cover in this already broad study all nutritional disorders, deficiencies and risks in an exhaustive manner, and therefore only those that appear of higher priority are considered. Following a presentation of nutritional opportunities, problems and risk factors in adolescence, general strategies and approaches are reviewed. More specific actions for the health sector to address nutritionrelated needs of adolescents are then discussed in the light of scientific evidence and lessons learned, while insisting on the importance of intersectoral approaches to nutrition in consideration of the multifactorial aetiology of nutrition problems
2 ADOLESCENCE PROVIDES A WINDOW OF OPPORTUNITY FOR NUTRITION A transitional period between childhood and adulthood.adolescence provides an opportunity to prepare for a healthy productive and reproductive life.and to prevent the onset of nutrition-related chronic diseases in adult life,while addressing adolescence-specific nutrition issues and possibly also correcting some nutritional problems originating in the past. 2.1 Adolescence is a timely period for the adoption and consolidation of sound dietary habits Adolescents are usually open to new ideas;they show curiosity and interest.Many habits acquired during adolescence will last a lifetime.Furthermore,with increasing age,adolescents'personal choices and preferences gain priority over eating habits acquired in the family,and they have progressively more control over what they eat,when and where(Thomas 1991;Shepherd and Dennison,1996;Spear 1996). One expression of adolescents'search to establish themselves as autonomous members of society is through a change in eating habits.For these reasons,adolescents are an ideal target for nutrition education. In younger children,parents are in charge and need to be influenced.In adults,it may be more difficult to modify well-established patterns.Furthermore,adolescents may not only adopt healthy eating patterns and lifestyles for themselves,but also influence their peers,family and other community members. Changes in lifestyle,including food habits,are often more obvious among urban adolescents,(Ahmed et al,1998),as they are typically the 'early adopters'owing,among other things to their attraction for novelty and high exposure to commercial marketing in cities.Indeed,looking into adolescents'living and eating patterns may give an idea of the changes taking place in a society.They may act as role models for others in the community,in particular if they are from higher socioeconomic status groups. In this sense,the patterns seen in urban well-off adolescents anticipate the patterns of the future.Since these privileged youth are a reference group for other adolescents,they should also be targeted by health and nutrition promotion activities. 2.2 Improving adolescents'nutrition behaviours is an investment in adult health Adolescents are in the process of establishing responsibility for their own health-related behaviours, including diet.It is therefore an appropriate time for health promotion programmes based on documented relationships between behaviour in this age group,obesity,cardiovascular and other chronic disease risk factors(see Chapter 3).Adolescents can and should take responsibility for their nutrition and the long-term repercussions on health.This may be quite a challenge,considering that adolescents tend to be little concerned with the future(Greene 1986),and long-term consequences of their present behaviours (Cordonnier 1995),but relevant strategies exist,based on an appropriate knowledge of personal and environmental determinants of food choice in this age group. Nutrition is only one aspect of health behaviours and the development of these in relation with chronic disease is better conceptualized in a 'chain of risk'framework(Kuh et al,1997).Over the life course, there may be an accumulation of biological and social risk.For instance,poor foetal nutrition(Barker et al,1990;Barker 1996),in combination with inadequate or adverse influence of parents,peers and the educational experience in childhood and adolescence,sets the stage for chronic disease in adult life, with additional risk coming from cultural influences and lifestyles.In other words,beyond biological NUTRITION IN A DO LESC E N CE /7
NUTRITION IN ADOLESCENCE / 7 2 ADOLESCENCE PROVIDES A WINDOW OF OPPORTUNITY FOR NUTRITION A transitional period between childhood and adulthood, adolescence provides an opportunity to prepare for a healthy productive and reproductive life, and to prevent the onset of nutrition-related chronic diseases in adult life, while addressing adolescence-specific nutrition issues and possibly also correcting some nutritional problems originating in the past. 2.1 Adolescence is a timely period for the adoption and consolidation of sound dietary habits Adolescents are usually open to new ideas; they show curiosity and interest. Many habits acquired during adolescence will last a lifetime. Furthermore, with increasing age, adolescents’ personal choices and preferences gain priority over eating habits acquired in the family, and they have progressively more control over what they eat, when and where (Thomas 1991; Shepherd and Dennison, 1996; Spear 1996). One expression of adolescents’ search to establish themselves as autonomous members of society is through a change in eating habits. For these reasons, adolescents are an ideal target for nutrition education. In younger children, parents are in charge and need to be influenced. In adults, it may be more difficult to modify well-established patterns. Furthermore, adolescents may not only adopt healthy eating patterns and lifestyles for themselves, but also influence their peers, family and other community members. Changes in lifestyle, including food habits, are often more obvious among urban adolescents, (Ahmed et al, 1998), as they are typically the ‘early adopters’ owing, among other things to their attraction for novelty and high exposure to commercial marketing in cities. Indeed, looking into adolescents’ living and eating patterns may give an idea of the changes taking place in a society. They may act as role models for others in the community, in particular if they are from higher socioeconomic status groups. In this sense, the patterns seen in urban well-off adolescents anticipate the patterns of the future. Since these privileged youth are a reference group for other adolescents, they should also be targeted by health and nutrition promotion activities. 2.2 Improving adolescents’ nutrition behaviours is an investment in adult health Adolescents are in the process of establishing responsibility for their own health-related behaviours, including diet. It is therefore an appropriate time for health promotion programmes based on documented relationships between behaviour in this age group, obesity, cardiovascular and other chronic disease risk factors (see Chapter 3). Adolescents can and should take responsibility for their nutrition and the long-term repercussions on health. This may be quite a challenge, considering that adolescents tend to be little concerned with the future (Greene 1986), and long-term consequences of their present behaviours (Cordonnier 1995), but relevant strategies exist, based on an appropriate knowledge of personal and environmental determinants of food choice in this age group. Nutrition is only one aspect of health behaviours and the development of these in relation with chronic disease is better conceptualized in a ‘chain of risk’ framework (Kuh et al, 1997). Over the life course, there may be an accumulation of biological and social risk. For instance, poor foetal nutrition (Barker et al, 1990; Barker 1996), in combination with inadequate or adverse influence of parents, peers and the educational experience in childhood and adolescence, sets the stage for chronic disease in adult life, with additional risk coming from cultural influences and lifestyles. In other words, beyond biological
programming,social patterning effects have to be considered.Adolescence may be a particularly relevant time for social patterning influences At least in certain population groups,another long-term benefit of improved nutrition in adolescence, particularly in girls,is the reduced risk of osteoporosis in older age.Calcium intake and bone deposition in adolescence are key factors of bone mineral mass later on in life,along with other determinants(see Chapter 3). Influencing nutrition-related behaviours of adolescents implies that they have some choice and,therefore, that they have access to the required food resources.This may not be so as adolescents generally have less resources than adults,while being more on their own than younger children.This is why interventions to enhance economic and food security of adolescents and more generally of households may be required in order for nutrition intervention to have sustainable impact.Conversely,improved health and nutrition may positively affect productivity and,therefore,long-term economic and food security(Delisle 1998a). 2.3 There is potential for correcting nutritional inadequacies and perhaps even for catch-up growth Adolescence is commonly regarded as a relatively healthy period of the life cycle.Indeed,adolescents are possibly less vulnerable to infection than they were at a younger age.This may contribute to their being somewhat neglected,but also it may mean that there is at adolescence less interference with adequate physiological utilization of food nutrients. Once final height is attained,stunting becomes a permanent consequence of past malnutrition rather than being a sign of present malnutrition.Growth retardation is common in poorer countries,and it occurs primarily during the first three years of life.The growth spurt of adolescence has been seen as a period of potential interest for catching up growth deficit of childhood.If there is indeed catch-up growth in height,adolescence can provide a final chance for intervention to promote additional growth, with potential benefit in terms of physical work capacity and for girls,of diminished obstetric risk(see also Chapter 3).However,evidence confirming catch-up growth during adolescence is still limited,and mostly indirect.Prolongation of the growth period due to delayed maturation associated with malnutrition can make up for some of the earlier growth retardation,in other words,there is some degree of spontaneous catch-up(Golden 1994).It is suggested,however,that total reversal to affluent societies'levels of final height would probably require cross-generational catch-up.A review of adopted children's studies suggests that catch-up growth through accelerated growth rates can be quite pronounced,but that it is not complete,and that it would be minimal in populations which continue to reside in the same place (Martorell,Kettel Khan and Schroeder,1994).It is possible that nutritional interventions induce an earlier and accelerated growth spurt,but it is not sure,based on available evidence, that it will affect final attained adult height,since it may then accelerate maturation,with a shortened growth period as a result.Remedial action in adolescence would be considered as coming late compared to that undertaken in infancy,but it may still be relevant,if shown to be effective in increasing lean body mass.However,catch-up growth intervention in adolescence will likely not improve other consequences of early growth retardation,in particular learning impairment(Martorell,Kettel Khan and Schroeder, ibid.).Furthermore,in adolescents who were born small because of intrauterine growth retardation, nutritional intervention for catch-up growth may result in gain in fat rather than in height(Leger and Czernichow,1999),as such individuals appear more prone to becoming obese. Studies undertaken as part of the adolescent research programme of the International Center for Research in Women(ICRW)contributed to knowledge about the extent of catch-up growth in height during adolescence,in the absence of or with food supplementation(Kurz and Johnson-Welch,1994).In the Philippines,it was found that over an eight-year period,adolescents aged 11-20 years from lower income households had completely caught up with those in the higher group,without supplementation.Findings from the Mexico study suggest partial spontaneous catch-up growth during adolescence.Children who were supplemented from the age of three months up to 10 years were still taller at age 18 than the non-
8/ programming, social patterning effects have to be considered. Adolescence may be a particularly relevant time for social patterning influences. At least in certain population groups, another long-term benefit of improved nutrition in adolescence, particularly in girls, is the reduced risk of osteoporosis in older age. Calcium intake and bone deposition in adolescence are key factors of bone mineral mass later on in life, along with other determinants (see Chapter 3). Influencing nutrition-related behaviours of adolescents implies that they have some choice and, therefore, that they have access to the required food resources. This may not be so as adolescents generally have less resources than adults, while being more on their own than younger children. This is why interventions to enhance economic and food security of adolescents and more generally of households may be required in order for nutrition intervention to have sustainable impact. Conversely, improved health and nutrition may positively affect productivity and, therefore, long-term economic and food security (Delisle 1998a). 2.3 There is potential for correcting nutritional inadequacies and perhaps even for catch-up growth Adolescence is commonly regarded as a relatively healthy period of the life cycle. Indeed, adolescents are possibly less vulnerable to infection than they were at a younger age. This may contribute to their being somewhat neglected, but also it may mean that there is at adolescence less interference with adequate physiological utilization of food nutrients. Once final height is attained, stunting becomes a permanent consequence of past malnutrition rather than being a sign of present malnutrition. Growth retardation is common in poorer countries, and it occurs primarily during the first three years of life. The growth spurt of adolescence has been seen as a period of potential interest for catching up growth deficit of childhood. If there is indeed catch-up growth in height, adolescence can provide a final chance for intervention to promote additional growth, with potential benefit in terms of physical work capacity and for girls, of diminished obstetric risk (see also Chapter 3). However, evidence confirming catch-up growth during adolescence is still limited, and mostly indirect. Prolongation of the growth period due to delayed maturation associated with malnutrition can make up for some of the earlier growth retardation, in other words, there is some degree of spontaneous catch-up (Golden 1994). It is suggested, however, that total reversal to affluent societies’ levels of final height would probably require cross-generational catch-up. A review of adopted children’s studies suggests that catch-up growth through accelerated growth rates can be quite pronounced, but that it is not complete, and that it would be minimal in populations which continue to reside in the same place (Martorell, Kettel Khan and Schroeder, 1994). It is possible that nutritional interventions induce an earlier and accelerated growth spurt, but it is not sure, based on available evidence, that it will affect final attained adult height, since it may then accelerate maturation, with a shortened growth period as a result. Remedial action in adolescence would be considered as coming late compared to that undertaken in infancy, but it may still be relevant, if shown to be effective in increasing lean body mass. However, catch-up growth intervention in adolescence will likely not improve other consequences of early growth retardation, in particular learning impairment (Martorell, Kettel Khan and Schroeder, ibid.). Furthermore, in adolescents who were born small because of intrauterine growth retardation, nutritional intervention for catch-up growth may result in gain in fat rather than in height (Léger and Czernichow, 1999), as such individuals appear more prone to becoming obese. Studies undertaken as part of the adolescent research programme of the International Center for Research in Women (ICRW) contributed to knowledge about the extent of catch-up growth in height during adolescence, in the absence of or with food supplementation (Kurz and Johnson-Welch, 1994). In the Philippines, it was found that over an eight-year period, adolescents aged 11-20 years from lower income households had completely caught up with those in the higher group, without supplementation. Findings from the Mexico study suggest partial spontaneous catch-up growth during adolescence. Children who were supplemented from the age of three months up to 10 years were still taller at age 18 than the non-
supplemented group,but the difference between groups had minimized.In contrast,the Guatemalan longitudinal study found that the gaps in height among children at age five remained the same at age 18 (Rivera et al,1995).In the metabolic study,also in Guatemala,it was found that levels of plasma insulin- like growth factor were somewhat higher in adolescents who had been receiving a supplement of 600 kilocalories per day for a sufficient time.However,the significance of changes in growth hormone levels in the short term for changes in stature over the long term is not known.In India(West Bengal),it was found that even within the same SES group,early menarche girls were heavier and taller than the late menarche girls(Bharati and Bharati,1998),which would suggest that even if a longer growth period allows for some catch-up,it does not fully compensate for the pre-existing deficit in stature.In a cross- sectional study on nutrition and diet of Chinese adolescents (Wang,Popkin and Zhai,1998),it was found that stunting was less prevalent in 1993 than two years earlier(19%vs 23%),which suggests that some catch-up growth in stature could have occurred with improving environmental conditions,but this is very indirect evidence Linear growth may be limited by multiple simultaneous nutrient deficiencies in many populations, which could explain that interventions with specific individual nutrients(vg,vitamin A,iron,zinc)have given conflicting results(Allen,1994).Overall quality of diets may be reflected in growth,as we observed in preschoolers(Tarini,Bakari and Delisle,1999).Once the deficiency in one single nutrient is corrected with the supplement,another nutrient may become limiting and reduce the growth response,and so forth,so that more research is needed to ascertain whether multinutrient dietary improvement (or supplementation)can enhance linear growth at the time of peak velocity,that is,around age 10-11 years,without accelerating maturational age beyond chronological age(Allen and Uauy,1994). Young girls can continue to grow during pregnancy(that is,after the adolescent growth spurt),from 2 up to 16 cm,according to Harrison et al(1985)who conducted a study in 69 primigravidae in Nigeria, among whom 59 were under 16 years.It seems that growth was correlated with red blood cell volume, and there was a close association of growth in height with iron and folic acid supplementation.This provides some evidence of positive effect of micronutrients on linear growth of adolescents even past the growth spurt,and hence,on the potential relevance of nutrition intervention in this regard.Further studies on the impact of multi-micronutrient supplementation on the onset and magnitude of the adolescence growth spurt have been recommended(Brabin and Brabin,1992);there is also a great need to study the effectiveness of controlled interventions improving the nutritional quality of diets. If there is indeed a window of opportunity for catch-up growth in adolescence through nutritional intervention,it is likely quite narrow,but it may extend beyond the adolescent growth spurt.However, further evidence of positive impact on height without encouraging obesity needs to be documented. Improved nutrition may accelerate maturation in adolescence,but this may also result in greater obesity in adulthood,as observed in the Amsterdam growth study(Post and Kemper,1993;van Lenthe,Kemper and van Michelen,1996).Similarly,further research on statural growth effects of multiple micronutrient supplements in adolescence is awaited.Notwithstanding some potential for catch-up growth in adolescent years,stunting in adolescence is best prevented during foetal life or infancy,as shown in longitudinal studies (see under Section 3.2.2). 2.4 Nutrition intervention in adolescent girls may contribute to breaking the vicious cycle of intergenerational malnutrition,poverty and chronic disease As emphasized by the Executive Director of UNICEF,one major reason for focusing on adolescents is that this period of a child's life is a unique opportunity to break a range of vicious cycles of structural problems that are passed from one generation to the next,such as poverty,gender discrimination,violence, poor health and nutrition. 7 See footnote 2,Web site:www.unicef.org/newsline/99pr6.htm,16/04/99 NUTRITION IN A DO LE SC E N CE /9
NUTRITION IN ADOLESCENCE / 9 supplemented group, but the difference between groups had minimized. In contrast, the Guatemalan longitudinal study found that the gaps in height among children at age five remained the same at age 18 (Rivera et al, 1995). In the metabolic study, also in Guatemala, it was found that levels of plasma insulinlike growth factor were somewhat higher in adolescents who had been receiving a supplement of 600 kilocalories per day for a sufficient time. However, the significance of changes in growth hormone levels in the short term for changes in stature over the long term is not known. In India (West Bengal), it was found that even within the same SES group, early menarche girls were heavier and taller than the late menarche girls (Bharati and Bharati, 1998), which would suggest that even if a longer growth period allows for some catch-up, it does not fully compensate for the pre-existing deficit in stature. In a crosssectional study on nutrition and diet of Chinese adolescents (Wang, Popkin and Zhai, 1998), it was found that stunting was less prevalent in 1993 than two years earlier (19% vs 23%), which suggests that some catch-up growth in stature could have occurred with improving environmental conditions, but this is very indirect evidence. Linear growth may be limited by multiple simultaneous nutrient deficiencies in many populations, which could explain that interventions with specific individual nutrients (vg, vitamin A, iron, zinc) have given conflicting results (Allen, 1994). Overall quality of diets may be reflected in growth, as we observed in preschoolers (Tarini, Bakari and Delisle, 1999). Once the deficiency in one single nutrient is corrected with the supplement, another nutrient may become limiting and reduce the growth response, and so forth, so that more research is needed to ascertain whether multinutrient dietary improvement (or supplementation) can enhance linear growth at the time of peak velocity, that is, around age 10-11 years, without accelerating maturational age beyond chronological age (Allen and Uauy, 1994). Young girls can continue to grow during pregnancy (that is, after the adolescent growth spurt), from 2 up to 16 cm, according to Harrison et al (1985) who conducted a study in 69 primigravidae in Nigeria, among whom 59 were under 16 years. It seems that growth was correlated with red blood cell volume, and there was a close association of growth in height with iron and folic acid supplementation. This provides some evidence of positive effect of micronutrients on linear growth of adolescents even past the growth spurt, and hence, on the potential relevance of nutrition intervention in this regard. Further studies on the impact of multi-micronutrient supplementation on the onset and magnitude of the adolescence growth spurt have been recommended (Brabin and Brabin, 1992); there is also a great need to study the effectiveness of controlled interventions improving the nutritional quality of diets. If there is indeed a window of opportunity for catch-up growth in adolescence through nutritional intervention, it is likely quite narrow, but it may extend beyond the adolescent growth spurt. However, further evidence of positive impact on height without encouraging obesity needs to be documented. Improved nutrition may accelerate maturation in adolescence, but this may also result in greater obesity in adulthood, as observed in the Amsterdam growth study (Post and Kemper, 1993; van Lenthe, Kemper and van Michelen, 1996). Similarly, further research on statural growth effects of multiple micronutrient supplements in adolescence is awaited. Notwithstanding some potential for catch-up growth in adolescent years, stunting in adolescence is best prevented during foetal life or infancy, as shown in longitudinal studies (see under Section 3.2.2). 2.4 Nutrition intervention in adolescent girls may contribute to breaking the vicious cycle of intergenerational malnutrition, poverty and chronic disease As emphasized by the Executive Director of UNICEF7 , one major reason for focusing on adolescents is that this period of a child’s life is a unique opportunity to break a range of vicious cycles of structural problems that are passed from one generation to the next, such as poverty, gender discrimination, violence, poor health and nutrition. 7 See footnote 2, Web site: www.unicef.org/newsline/99pr6.htm, 16/04/99
Preparing for the demands of childbearing and breastfeeding is timely in adolescent girls and,above all, preventing premature pregnancy and its associated risk for both mother and child.Early intervention is particularly critical in adolescent girls whose nutritional status is marginal to begin with,so that they enter their first pregnancy in a better nutritional state.Improving adolescent girls'nutrition has the following reproduction-related benefits(Gillespie 1997): increased pre-pregnancy weight and body stores of nutrients,thus contributing to improved future pregnancy and lactation outcome,while preserving the mother's nutritional status and well-being; improved iron status with reduced risk of anaemia in pregnancy,low birth weight,maternal morbidity and mortality,and with enhanced work productivity and perhaps linear growth; improved folate status,with reduced risk of neural tube defects in the newborn and megaloblastic anaemia in pregnancy. Small girls are likely to become small women who are more likely to have small babies,particularly if at a young age(see Chapter 3).Improving adolescent girls'nutrition and delaying their first pregnancy may be a promising intervention point to break this intergenerational cycle of malnutrition(ACC/SCN 1992b;UNICEF 1998).In Guatemala for example,maternal height,which is considered a proxy for both genetic and environmental influences,was a significant determinant of child size at 3 years,and even at adolescence when controlling for size at 3 years.This again underlines the intergenerational pattern of malnutrition(Kurz and Johnson-Welch,1994). There is growing evidence that foetal (and early infancy)malnutrition may be involved as a risk factor for chronic diseases in later life,in particular coronary heart disease,type-2 diabetes,and metabolic disease(Barker 1994).Thus,improving adolescent girls'nutrition before pregnancy(and during,but it is a second choice)may also contribute to break the vicious cycle of malnutrition,poverty and chronic disease. Improving adolescent girls'nutrition has benefits other than for reproduction.The well-being and long- term nutritional health of women are legitimate goals in themselves.Women are also the key to household food safety and nutrition(Quisumbing et al,1998).Improving their nutritional status and enhancing their nutrition-related skills is therefore likely to have long-range benefits for themselves and their families. 2.5 Reaching households and communities through adolescents Many adolescents are in school,which provides an effective and efficient opportunity for reaching large portions of the population beyond students themselves:school personnel,families,community members (WHO 1996a).In Ecuador,the school nutrition programme successfully relied on this strategy of school children as agents of change at the household level(Chauliac et al,1996a).However,a large proportion of adolescents are likely to be out of school at an early age in many low-income countries,in which case other strategies of reaching adolescents in person are needed,beyond impersonal communication through the media. The peer approach to health education,for example,which is widely used throughout Latin America because of its effectiveness,allows to reach not only peers of the adolescents involved,but also other youth in their environment.It may use as a entry point the school,or another community-based institution.Also,the participation of youth in health education allows them to develop relations with adults outside their family and to acquire a sense of responsibility and belonging within a social group (Pommier et al,1997). As noted for Brazil(Doyle and Feldman,1997),young people acquire work and family responsibilities at an earlier age in poorer countries than their European or American counterparts and,therefore,the family unit may be reached through this group. 10/
10/ Preparing for the demands of childbearing and breastfeeding is timely in adolescent girls and, above all, preventing premature pregnancy and its associated risk for both mother and child. Early intervention is particularly critical in adolescent girls whose nutritional status is marginal to begin with, so that they enter their first pregnancy in a better nutritional state. Improving adolescent girls’ nutrition has the following reproduction-related benefits (Gillespie 1997): • increased pre-pregnancy weight and body stores of nutrients, thus contributing to improved future pregnancy and lactation outcome, while preserving the mother’s nutritional status and well-being; • improved iron status with reduced risk of anaemia in pregnancy, low birth weight, maternal morbidity and mortality, and with enhanced work productivity and perhaps linear growth; • improved folate status, with reduced risk of neural tube defects in the newborn and megaloblastic anaemia in pregnancy. Small girls are likely to become small women who are more likely to have small babies, particularly if at a young age (see Chapter 3). Improving adolescent girls’ nutrition and delaying their first pregnancy may be a promising intervention point to break this intergenerational cycle of malnutrition (ACC/SCN 1992b; UNICEF 1998). In Guatemala for example, maternal height, which is considered a proxy for both genetic and environmental influences, was a significant determinant of child size at 3 years, and even at adolescence when controlling for size at 3 years. This again underlines the intergenerational pattern of malnutrition (Kurz and Johnson-Welch, 1994). There is growing evidence that foetal (and early infancy) malnutrition may be involved as a risk factor for chronic diseases in later life, in particular coronary heart disease, type-2 diabetes, and metabolic disease (Barker 1994). Thus, improving adolescent girls’ nutrition before pregnancy (and during, but it is a second choice) may also contribute to break the vicious cycle of malnutrition, poverty and chronic disease. Improving adolescent girls’ nutrition has benefits other than for reproduction. The well-being and longterm nutritional health of women are legitimate goals in themselves. Women are also the key to household food safety and nutrition (Quisumbing et al, 1998). Improving their nutritional status and enhancing their nutrition-related skills is therefore likely to have long-range benefits for themselves and their families. 2.5 Reaching households and communities through adolescents Many adolescents are in school, which provides an effective and efficient opportunity for reaching large portions of the population beyond students themselves: school personnel, families, community members (WHO 1996a). In Ecuador, the school nutrition programme successfully relied on this strategy of school children as agents of change at the household level (Chauliac et al, 1996a). However, a large proportion of adolescents are likely to be out of school at an early age in many low-income countries, in which case other strategies of reaching adolescents in person are needed, beyond impersonal communication through the media. The peer approach to health education, for example, which is widely used throughout Latin America because of its effectiveness, allows to reach not only peers of the adolescents involved, but also other youth in their environment. It may use as a entry point the school, or another community-based institution. Also, the participation of youth in health education allows them to develop relations with adults outside their family and to acquire a sense of responsibility and belonging within a social group (Pommier et al, 1997). As noted for Brazil (Doyle and Feldman, 1997), young people acquire work and family responsibilities at an earlier age in poorer countries than their European or American counterparts and, therefore, the family unit may be reached through this group