Adolescent Growth

by Kathleen M. Kurz, PhD, International Center for Research on Women, Washington, D.C.

It is important to consider nutritional status during adolescence (defined here as ages 10 to 19), in addition to other stages such as early childhood and pregnancy. Adolescence is a time to prepare for the nutritional demands of pregnancy, lactation, and heavy workloads that girls will soon experience, if they have not already. Adolescence is a time of accelerated growth in stature, after which final height is achieved. The focus of this article is on adolescent growth with an emphasis on height. Also, girls are emphasized over boys within the maternal and child nutrition focus of this issue.

Patterns of growth during adolescence are outlined, as well as effects of pregnancy. Selected studies are reviewed on the potential for catch-up growth in height. Then the issues to consider before implementing one possible nutritional intervention (a food intervention) are addressed. Finally, other critical interventions for adolescents regarding maternal and child nutrition are suggested. Some results are drawn from the Nutrition of Adolescent Girls Research Program at the International Center for Research on Women (ICRW), funded by USAID Office of Nutrition. This program is a set of 11 research projects in Asia, Africa, and Latin America and the Caribbean investigating the factors related to the nutrition status of girls and boys aged 10-19 years (Kurz et al, 1994).

Patterns of Growth

A growth spurt occurs during adolescence as a part of maturation, which is hormonally-driven. Weight and height velocity are greater than between ages 5 and 10. Growth occurs in the skeleton, in the muscles, and in almost every system and organ of the body, except the brain and head (Tanner, 1972).

Growth in height is most rapid during several years prior to menarche, with onset of the growth spurt occurring between the ages of 10 - 14 years. Peak height velocity occurs about one to one and a half years before menarche. Additional height is gained after peak height velocity (10.8 - 22.3 cm) and after menarche (7.4 - 10.6 cm). This additional height may be gained over a period of 4.7 years after menarche (Tanner, 1972). Growth of the pelvic bones, critical for preventing obstructed labour, occurs for several more years after height is complete (Moerman, 1982).

Pregnancy During Adolescence

Pregnancy during adolescence carries many health risks. The risks of maternal and neonatal mortality are much greater for adolescents than adult women. They are also at increased risk of delivering babies preterm, and with low birthweight. The low birthweight of babies born to adolescent mothers is more than a case of small babies from small mothers. Young, still-growing adolescents, even when matched for nutritional status, have smaller newborns than adult mothers (Frisancho et al., 1985).

There are numerous factors that may contribute to this increased risk, including less use of prenatal care and obstetric services by adolescents. Of increased interest in recent years is investigation into the possible competition for nutrients between the adolescent and her foetus. Using knee height as the indicator to avoid the measurement problem of “shrinkage” of stature during pregnancy, Scholl et al. (1990) found that birthweight was compromised when adolescents were still growing, but not when they had stopped growing in stature. It is known that the height gained in the adolescent growth spurt continues during pregnancy. It is not known if this growth is slowed to any degree as a result of the pregnancy, but it is known that iron and folic acid supplementation and antimalarial treatment promoted growth in undernourished, pregnant Nigerian adolescents compared to placebo controls (Harrison et al., 1985).

As the variation in the patterns of growth suggest, stature can be completed as early as age 16 (Roche & Davila, 1972) or as late as age 23, and pelvic growth several years subsequent. In populations with chronic undernutrition, maturation is typically delayed, tending toward the later age for completed stature. If the risks of pregnancy concomitant with adolescent growth are to be avoided, then pregnancy should be postponed until a woman is at least 19 years old. Menarche is not a good marker for optimal readiness to reproduce because growth continues for 4-7 years afterward.

Catch-Up Growth

Evidence about the potential for catch-up growth in height during adolescence is limited. The greatest limitation is that no studies of boys or non-pregnant girls address whether intervention during adolescence could promote a greater height gain than would be expected from the normal growth spurt during adolescence (though one study described in the next section assessed the response of growth hormones to a food intervention). Selected evidence from adoption studies and longitudinal studies is reviewed below to explore whether adolescents who were undernourished during early childhood “catch-up” in height, despite no intervention during adolescence, compared to their peers who were better nourished in early childhood.

The study of adoption cases is useful because the “intervention” (being raised in a middle-class family instead of a poor one) is so large. What can be assessed is perhaps the greatest potential for catch-up growth among stunted children. (The clinical literature on disease-related causes of growth failure, and subsequent catch-up growth, as reviewed by Largo (1993), also illustrates the large potential for catching up.) In the adoption studies, catch-up growth was quite marked (as reviewed by Martorell et al, 1994). In the four studies reviewed, all children were adopted by age 5. They show that catch-up growth in height begins whenever the adoption or change in circumstances occurs. They also show that final height of the adoptees is greater than for the comparison group of undernourished who had no such change in circumstances, though it is still below the 50th percentile of international reference data. This suggests that much stature can be recovered, but not all, even under these optimal new conditions.

According to longitudinal studies in which no change in residence occurred, partial catch-up occurred during adolescence in three of the four cases reviewed below. The cases where no-catch growth was found is presented first. Martorell et al. (1990) compared three groups of rural Guatemalan adolescents at age 18 according to their degree of stunting at age 5. All had received either a high- or a low-calorie food supplement from birth to 7 years of age in the INCAP Four Village study. The gap in height that existed among the three groups at age 5 (due in large part to greater height of the group which received high-calorie supplementation) continued to the same degree until age 18, and the authors concluded that no catch-up growth occurred during adolescence. They are investigating this further under the ICRW/USAID program.

Bouis et al. (1994) compared the height of persons aged 7-20 years in 1992 from Bukidnon, The Philippines with their height eight years earlier, 1984. No food supplementation was given between 1984 and 1992. When heights were compared between two groups in 1992 according to the degree of stunting in 1984, the results were similar to Martorell et al. (1990), that is, no catch-up growth was indicated. They argued, however, that the choice of groups was biased against finding catch-up growth because stature at the younger ages had a genetic as well as an environmental component. To reduce this bias, they reanalyzed their data comparing two groups in 1992 according to the adolescents’ family incomes in 1984. Persons from lower income households in 1984 were somewhat shorter than persons from higher income households. The data in 1992 suggest that older adolescents from lower income households had completely caught up in height to those in the higher income group. The choice of comparison groups seems to have a strong influence on the extent of catch-up growth reported.

Chavez et al. (1994) compared a small group of rural Mexican adolescents who had received food supplementation in childhood (from 3 months to 10 years of age) and their matched non-supplemented counterparts in the same village. The supplemented children were taller than their non-supplemented peers throughout childhood. During adolescence the difference narrowed but did not disappear, indicating that partial catch-up growth occurred.

Satyanarayana et al (1981) compared three groups of rural Indian adolescents at age 18 according to their degree of stunting at age 5. There was no supplementation in early childhood. Incremental growth in height during puberty among girls who were the most stunted at age 5 was significantly greater than those least stunted, but their final height at age 18 still lagged behind, indicating that partial catch-up growth occurred.

Issues to Consider Before Designing a Food Intervention

Beyond the limited information above suggesting that partial catch-up growth can occur, there is virtually no information on whether intervention during adolescence could promote a greater height gain than would be expected from the normal growth spurt. A food intervention is considered here, because it is commonly considered by those, trying to improve nutritional status. The mechanism by which partial catch-up growth occurred in three of the studies described above is not known. The degree to which dietary changes are involved in the mechanism is also not known. It is known that partial catch-up occurred without a designed intervention during adolescence, but the extent of dietary changes occurring at home over the adolescent years is not known. It has recently been suggested that regression-to-the-mean occurs in height data during adolescence in a well-nourished population (Cole, 1994), and could be considered for undernourished populations as well. Before designing studies to test the efficacy of interventions promoting adolescent growth, consideration should be given to some important questions listed below.

1. How much height could be gained with food intervention?

Only one known study has assessed the effects of a food intervention during adolescence on the potential for growth in height. Torun and colleagues (1994) found that levels of plasma insulin-like growth factor (IGF) were somewhat higher among the 24 pre-menarcheal participants of their metabolic study in Guatemala City when 4 cookies and a drink providing about 600 extra kilocalories per day were consumed. A crossover design was employed, and this result was observed during only the second 3-month intervention period. Hormone levels were the outcome measures of this study, serving as indicators of the potential for gains in height, because the short duration of the study did not allow time for significant gains in height. Thus, despite the wealth of information in this study, it does not address how much height can be gained with food intervention.

2. Is menarche hastened? If so, what are the implications?

Well-nourished girls tend to achieve menarche at an earlier age than girls with poor nutritional status. For example, the mean of the NCHS sample (representative of the U.S. population) is 12.8 years. The average or median age of menarche could be 13-15 years in populations with chronic, but not severe, undernutrition. As stated above, the fastest growth during adolescence occurs before menarche.

Growth velocities are generally greater for adolescents who mature early than for those who mature late. Among well-nourished adolescents, this means that early maturers grow in height faster before menarche for a shorter period of time, late maturers grow slower before menarche for a longer period of time, and the total height achieved during adolescence may be similar for both.

It is not known how intervening with extra food during adolescence will influence this balance. If the intervention is pre-menarcheal to take advantage of the faster growth, will it hasten menarche and shorten the length of time during which the faster growth occurs (Martorell et al., 1994)? Menarche is known to occur earlier among girls whose food intake was improved starting in early childhood, but the effects on menarcheal age of a later intervention, during adolescence, have not been investigated. Ultimately, will the total growth in height during adolescence be more than without the intervention? If so, as would be hoped, how much more? If the intervention is post-menarcheal to avoid any potential hastening of menarche, can much extra growth in height (or pelvic size) be achieved during this interval of slower growth?

3. How much fat is gained simultaneously?

A food intervention during adolescence aimed at increasing final stature will also cause an increase in weight, partially fat stores. Whether or not this is advantageous depends on existing weight and fat stores. If underweight among adolescents is prevalent, then a food intervention could contribute to reducing the prevalences of both underweight and stunting. It would also be expected to contribute to fewer low birthweight babies once the adolescents reproduce. However, if underweight is not prevalent, despite a high prevalence of stunting, then any benefits of greater stature must be weighed against the potential for promoting overweight.

Recommendations - Other Interventions for Adolescent Nutritional Status

If there are numerous questions to consider before designing a food intervention, what can be recommended now to prepare adolescent girls for the nutritional demands of pregnancy, lactation, and heavy workloads they will soon experience. Regarding maternal and child nutrition, three recommendations are critically important:

1. Promote growth during early childhood, especially 0-3 years.

A very good time to promote growth in height is in early childhood, especially 0-3 years. At this time growth is rapid, children are vulnerable to growth faltering due to infectious diseases and malnutrition, and it is known they respond to food supplementation. Improvements in nutritional status at this early age will yield many benefits, including their cognitive development and physical capacity. The ways to improve nutritional status have been explored extensively, and include preventing diarrhoeal diseases through clean water and other interventions, and promoting breastfeeding and the intake of nutrient-dense weaning foods, and psychosocial stimulation (Grantham-McGregor et al, 1991).

2. Improve iron status before the first pregnancy.

Iron is needed for growth, and iron supplementation of iron-deficient children is known to promote growth in both pregnant adolescents (Harrison et al, 1985) and pre-pubertal school children (Latham et al, 1990). High rates of anaemia among adolescents were found (16-55%) in six of the seven studies under ICRW’s Nutrition of Adolescent Girls Research Programme, in which it was assessed (Kurz et al, 1994). Improving adolescents’ iron status should be included in new efforts of the reproductive health and family planning experts to reach adolescents. Interventions fit well with the clinic orientation, including increasing iron intake through supplementation and promoting the consumption of iron-rich foods, and decreasing iron loss through treatment of parasitic infections that cause iron loss, such as hookworm and schistosomiasis. These interventions need not be limited to adolescence. Increased iron intake and decreased parasitic infection would be beneficial to many age groups.

3. Postpone the first pregnancy.

Pregnancy and lactation are nutritionally demanding, especially when added to everyday energy demands. If adolescence is when the pregnancy occurs, growth itself is a third set of nutritional demands. Postponing pregnancy until after adolescence (at least 19 years) is a key strategy for maintaining or improving the nutritional status of adolescent girls and women. Some strategies for postponing pregnancy are delaying the age of marriage, or delaying age of sexual activity, and promoting use of family planning among adolescents for whom pregnancies would be unwanted.

Reproductive health and family planning experts are giving new attention to reaching adolescents as the number of their pregnancies increases worldwide, particularly among unmarried girls. Although the higher risks of adolescent pregnancy have long been recognized, reaching adolescents is only starting to be a priority. Adolescents are not reached through standard family planning approaches. New approaches are being attempted, only now in their early stages.

References

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Chavez, A., Martinez, C., Soberanes, B., Dominguez, L., & Avila, A. (1994) Early Nutrition and Physical and Menial Development in Mexican Rural Adolescent Females. International Center for Research on Women, Nutrition of Adolescent Girls Research Program, No. 4.

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Satyanarayana, K., Nadamuni Naidu, A., Swaminathan, M.C. & Narasinga Rao, B.S. (1981) Effect of Nutritional Deprivation in Early Childhood on Later Growth - A Community Study Without Intervention. American Journal of Clinical Nutrition, 34, 1636-1637.

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Torun, B., Viteri, F.E., Ramirez-Zea, M., Rodriguez, M.M. & Guptill, K. (1994) Response of Endogenous Growth Factors to Exercise and Food Supplementation in Stunted Pubertal Girls in Guatemala. International Center for Research on Women, Nutrition of Adolescent Girls Research Program, No. 2, forthcoming.