Adolescent Nutrition: Requirements, Deficiency Risks, and the Second Window of Opportunity

In Ethiopia, national survey data show that 38.2% of adolescent girls aged 15–19 are anaemic, a prevalence that rises above 45% in the Afar and Somali regions where pastoralist dietary patterns and early marriage converge with structural poverty.¹ Across the broader Sub-Saharan African (SSA) region, stunting rates among adolescents remain alarmingly high - Ghana’s 2022 Demographic and Health Survey recorded that more than one in five adolescent boys aged 10–14 were stunted, a legacy of inadequate early childhood nutrition that the pubertal growth spurt cannot fully reverse. These figures are not anomalies. They reflect a long-standing policy architecture that has oriented its energy and financing almost exclusively towards children under five, leaving the nutritional needs of adolescents to accumulate quietly in the background of global health discourse.

This oversight is particularly difficult to justify given what is now understood about the developmental significance of the second decade of life. The concept of adolescent nutrition as a distinct domain of enquiry has gained substantial traction since Bundy and colleagues published the landmark Disease Control Priorities volume on child and adolescent health,² which argued forcefully that the investments and policy attention concentrated on the “first 1,000 days” from conception to age two represent only one of two critical biological windows. The adolescent period constitutes a second. Understanding its nutritional demands - and the particular risks that converge upon adolescents in SSA - is the central task of this review.

The Second Window of Opportunity: Scientific Basis

The conceptual framework of the “second window of opportunity” builds on the earlier literature around critical developmental periods and nutritional programming. Victora and colleagues, drawing on birth cohort data from Brazil, Guatemala, India, the Philippines, and South Africa, demonstrated that nutritional deficits established in the first two years of life carry long-term consequences for adult productivity, chronic disease risk, and reproductive outcomes - but that adolescence represented a further period when biological plasticity, though diminished, remains clinically meaningful.³ Prentice and colleagues extended this framework by defining the mechanisms through which adolescent catch-up growth operates, identifying bone mineralisation, lean mass accretion, and cognitive consolidation as the primary domains in which nutritional inputs during puberty exert lasting effects.⁴

The physiological rationale is straightforward. Puberty triggers a remarkable acceleration in somatic growth: adolescent boys gain approximately 25–28 cm in height and 20 kg in lean body mass during the pubertal growth spurt, while girls accumulate critical fat depots and bone mineral density in preparation for reproductive function. Rogol and colleagues documented that nutritional adequacy during puberty is a determinant of adult height, bone density at peak, and reproductive competence - with undernutrition during this period suppressing both the magnitude and duration of the growth spurt and, in severe cases, delaying pubertal onset by two to four years.⁵ The implications for SSA populations, where dietary diversity is constrained and energy intake is frequently inadequate, are considerable.

Critically, the second window is also characterised by irreversibility once it closes. Bone density accumulation reaches approximately 90% of its peak by age 18–20; linear growth ceases with epiphyseal fusion; and the cognitive architecture established during adolescence shapes adult human capital in ways that nutritional correction in the third decade of life cannot meaningfully alter. This temporal specificity - the window is real, it opens fully during early-to-mid adolescence, and it closes - demands that nutritional interventions be timed accordingly, rather than deferred to adult health programmes.

Macronutrient Requirements During Adolescence

Energy requirements during adolescence exceed those of any other post-infancy life stage on a per kilogram basis, driven by the energetic demands of somatic growth, pubertal hormonal activity, and, in SSA contexts, the substantial physical labour that many adolescents contribute to household agricultural production. The World Health Organisation’s estimated average requirement for energy among adolescent boys aged 14–18 is approximately 3,000–3,300 kcal per day; for girls of equivalent age, 2,200–2,500 kcal depending on physical activity level and stage of sexual maturation. These figures sit well above the consumption levels documented in dietary surveys across rural Ethiopia, northern Nigeria, and northern Ghana, where median energy intake among adolescents commonly falls 20–30% below age-specific requirements.

Protein requirements are similarly elevated. During peak growth velocity, protein synthesis for muscle accretion requires an intake of approximately 1.1–1.2 g/kg body weight per day in adolescent males and 0.9–1.0 g/kg in females. In SSA dietary patterns dominated by maize, sorghum, and cassava-based staples, protein quality - as reflected in the digestible indispensable amino acid score - is frequently insufficient even when total protein intake meets minimum thresholds. Animal-source foods, which provide the most bioavailable protein and serve simultaneously as vehicles for haem iron, zinc, and vitamin B12, are consumed infrequently in lower-income SSA households. Black and colleagues identified inadequate protein and energy intake as contributors to the 165 million cases of stunting globally, with the greatest burden in SSA and South Asia - a burden that is reproduced at each generational cycle when stunted adolescent girls enter pregnancy without adequate nutritional reserves.⁶

Essential fatty acids, including the long-chain polyunsaturated fatty acids critical for ongoing neurological development, are a further area of concern. Adolescent cognitive development, including the maturation of prefrontal executive function that continues well into the early twenties, relies on adequate docosahexaenoic acid (DHA) availability. Fish consumption in SSA varies greatly by geography - coastal communities in southern Ghana maintain higher seafood intakes - but inland populations in Ethiopia and northern Nigeria frequently have minimal access to DHA-rich foods, a gap that fortification and diversification programmes have yet to address systematically.

Micronutrient Requirements: Iron, Calcium, Zinc, and Folate

Iron

Iron is the micronutrient most consistently deficient among SSA adolescents, and its consequences during the second decade of life are well established. The pubertal surge in lean mass creates a substantial increase in iron demand for myoglobin and mitochondrial respiratory enzymes, while adolescent girls face the additional monthly loss of menstrual blood - an average of 30–40 mL per cycle, representing a further iron loss of approximately 15–20 mg per month. Gebremedhin and colleagues, in a cross-sectional study of over 2,000 adolescents across Ethiopia, found an overall anaemia prevalence of 30.1%, with female sex, rural residence, and low dietary diversity score independently and significantly associated with anaemia after multivariate adjustment.¹ The study is notable for its adolescent-specific focus - the majority of Ethiopian nutrition surveys have concentrated on under-five and pregnant-woman populations - and its findings align with broader SSA evidence reviewed by Patton and colleagues in the second Lancet adolescent health series.⁷

Dietary iron in SSA is predominantly non-haem iron from legumes and cereals, whose bioavailability is substantially inhibited by phytates, tannins, and calcium. A diet centred on teff and sorghum injera in Ethiopia, or maize and cowpea in Nigeria, may deliver adequate total iron by weight but provide only a small fraction in absorbable form. The inhibitory effect of high-phytate diets on non-haem iron absorption has been quantified at reductions of up to 65–80% relative to reference diets, underscoring why dietary iron intake data alone cannot substitute for biomarker-based anaemia surveillance.

Calcium

Adolescence is the primary window for bone mineralisation, with approximately 40% of adult bone mass accrued between the ages of 11 and 17. Daily calcium requirements during peak bone accretion are estimated at 1,200–1,300 mg, yet dietary surveys across SSA consistently document intakes well below half this level among school-age adolescents. The paradox - that SSA populations with very low calcium intakes do not universally exhibit the osteoporosis rates predicted by Western epidemiological models - has prompted considerable scientific debate. Prentice and colleagues proposed that adaptive mechanisms, including reduced urinary calcium excretion and enhanced intestinal absorption efficiency, partially compensate for low intake, but also cautioned that these adaptations are not unlimited and that under conditions of concurrent vitamin D insufficiency, the skeletal consequences of low calcium intake become more pronounced.⁴

In Ghana, the National Nutrition Policy has acknowledged that adolescent calcium intake, particularly in northern Ghana where dairy consumption is minimal, represents a gap that existing fortification infrastructure does not address. This is compounded by the fact that calcium supplementation programmes are almost entirely absent from adolescent health budgets in SSA, in contrast to the iron and folate supplementation initiatives that have received donor attention.

Zinc

Zinc is required for somatic growth, immune competence, sexual maturation, and DNA synthesis - biological processes that are all operating at accelerated rates during puberty. The estimated prevalence of zinc deficiency in SSA populations has been placed at approximately 25–45% depending on country and dietary context, based on modelling from the International Zinc Nutrition Consultative Group. Deficiency during adolescence is associated with delayed pubertal development, impaired linear growth, reduced immune response to infection, and poor wound healing - the last being clinically significant in SSA contexts where adolescent girls experience high rates of skin infections, genital injuries related to early sexual activity, and obstetric complications.

In Nigeria, dietary zinc intake data from nationally representative surveys reveal that zinc consumption from animal-source foods - the most bioavailable dietary zinc source - is concentrated in urban and higher-income quintiles, while rural adolescents in the north-west and north-east zones of the country depend almost entirely on plant-source zinc of low bioavailability. Bhutta and colleagues, synthesising evidence on nutrition-specific interventions in their landmark 2013 Lancet review, found that zinc supplementation produced measurable reductions in diarrhoea incidence and stunting prevalence in children, but emphasised that adolescent-specific trial data remained scarce.⁸

Folate

Folate requirements increase substantially during adolescence due to rapid cell proliferation, DNA synthesis during pubertal growth, and - particularly for adolescent girls - the need to establish adequate folate stores prior to pregnancy. Neural tube defects (NTDs), which arise from folate insufficiency in the periconceptional period, are heavily concentrated in populations where adolescent pregnancies are common and folate status is poor. In SSA, this epidemiological overlap is acute: adolescent birth rates in Nigeria and Ethiopia remain among the highest globally, and the gap between the onset of sexual activity and first antenatal contact - during which folate supplementation typically begins - means that the embryonic period of maximal NTD risk frequently passes without any supplementation coverage. The case for universal iron and folic acid (IFA) supplementation targeted at all adolescent girls, not only those who are pregnant, rests substantially on this logic.

SSA Dietary Patterns and Structural Constraints

Dietary patterns among SSA adolescents are shaped by the intersection of food system constraints, household poverty, gender norms, and school attendance. The dominant dietary pattern across much of the region is characterised by starchy staples providing 60–75% of energy, low diversity of vegetables and fruits, minimal animal-source food consumption, and heavy reliance on a small number of legumes - primarily beans and groundnuts - for protein. The Women’s Dietary Diversity Score adapted for adolescents consistently reveals that fewer than 30% of adolescent girls in Ethiopia, Ghana, and Nigeria consume five or more food groups in a 24-hour period, a threshold associated with adequate micronutrient adequacy.

Street food consumption is an increasingly important contributor to adolescent energy intake in urban SSA, but the nutritional quality of available street foods - dominated by fried dough, sweetened beverages, and refined carbohydrates - offers limited micronutrient benefit while contributing to emerging burdens of overweight in urban adolescent populations. This dual burden, in which stunting and micronutrient deficiency coexist with urban overweight, has been documented in secondary analyses of Demographic and Health Survey data from Ghana and Nigeria, and it complicates the design of population-level dietary guidance that must serve both ends of the nutritional spectrum simultaneously.

Unique Vulnerability Profiles: Early Marriage, School Dropout, and Adolescent Pregnancy

The nutritional needs of adolescents do not exist in isolation from the social conditions that structure their lives. In SSA, three social exposures substantially amplify nutritional risk: early marriage, school dropout, and adolescent pregnancy. These are not independent variables - they form a cascading sequence in which girls who marry before age 18 disproportionately leave school, become pregnant during physiological adolescence, and face compounded demands on nutritional reserves that are already depleted.

In Niger and Mali - at the extreme end of the SSA spectrum - more than 75% of girls are married before age 18. In Ethiopia, the median age at first marriage in rural Amhara and Afar regions remains below 17 years. Adolescent girls who are pregnant require not only the micronutrient intakes necessary to sustain fetal development but must also meet the continuing demands of their own growth - a dual burden on iron, calcium, zinc, and folate simultaneously. The maternal mortality consequences of adolescent pregnancy are well documented by Patton and colleagues, who established that complications of pregnancy and childbirth are the leading cause of death among girls aged 15–19 globally.⁷

School dropout amplifies nutritional risk through two pathways. First, it removes adolescents from the school-based platforms through which micronutrient supplementation, deworming, and nutrition education are most efficiently delivered at scale. Second, out-of-school adolescents - particularly girls engaged in domestic labour or early marriage - are less likely to be reached by community health worker programmes calibrated around household visits for mothers of young children. For a fuller examination of how surveillance systems can extend their reach to out-of-school adolescents, the conceptual and operational framework described in implementing Health and Demographic Surveillance Systems is instructive.

Interventions: School Feeding, IFA Supplementation, and Life Skills Programming

The evidence base for adolescent nutrition interventions in SSA, whilst less developed than that for under-five programmes, has strengthened considerably over the past decade. Three categories of intervention have attracted the most programmatic attention.

School feeding programmes have been evaluated across multiple SSA contexts for their capacity to improve dietary intake, attendance, and - where meals include animal-source foods or micronutrient-fortified products - micronutrient status. The World Food Programme’s Home-Grown School Feeding model, implemented in Ghana since 2005, has demonstrated improvements in school enrolment, attendance, and dietary diversity among primary school-age children; its extension to secondary level is more limited but is increasingly prioritised in the national school health agenda. A key structural limitation, however, is that school feeding is by definition conditional on school attendance - it cannot reach the substantial minority of adolescents who have dropped out, precisely the subgroup with the highest nutritional risk.

Iron and folic acid (IFA) supplementation targeted at adolescent girls is among the most cost-effective nutrition interventions available, with cost-effectiveness estimates from South Asia placing the cost per disability-adjusted life year averted at below US$100 under favourable programme conditions. The WHO currently recommends weekly IFA supplementation for all menstruating adolescent girls in settings where anaemia prevalence exceeds 20%. Implementation in SSA has been uneven: Ethiopia has integrated weekly IFA into its school health programme since 2013, with coverage estimates suggesting approximately 40% of enrolled adolescent girls receive supplements consistently. Nigeria’s programme remains fragmented at state level, with implementation quality varying markedly between the north-west - where burden is highest - and the south, where health infrastructure is more robust. Ghana’s programme has benefited from systematic donor coordination but faces persistent supply chain disruptions.

The interaction between IFA supplementation and malaria merits specific attention. In malaria-endemic SSA, iron supplementation in iron-replete individuals can increase susceptibility to malaria by providing iron to plasmodium parasites. Current WHO guidance therefore recommends that IFA supplementation in malaria-endemic settings be accompanied by malaria prevention measures, including insecticide-treated bed nets and where feasible intermittent preventive treatment. Programme designs that ignore this interaction risk producing adverse outcomes in the very populations they aim to protect.

Life skills and nutrition education programming, delivered through schools, community health clubs, and increasingly mobile platforms, has shown modest but meaningful effects on dietary knowledge, infant and young child feeding practices among adolescent mothers, and anaemia-related health-seeking behaviour. The evidence from SSA is reviewed in the context of broader micronutrient policy in our analysis of the role of micronutrient interventions in adolescent health policy , which examines structural efficacy and compliance challenges across multiple programme types.

Bhutta and colleagues, in their Lancet series review of nutrition-specific and nutrition-sensitive interventions, identified that the combination of direct nutrition interventions (supplementation, fortification) with nutrition-sensitive programming (education, social protection, agriculture) achieves synergistic effects not achievable by either approach alone.⁸ This finding has direct implications for adolescent nutrition programming in SSA, where the social determinants of dietary behaviour - gender norms, school enrolment, access to diverse foods - cannot be altered by supplementation alone.

Country-Specific Profiles

Ethiopia presents a high-burden context defined by geographic heterogeneity. The Ethiopian National Nutrition Programme (NNP) has explicitly incorporated adolescent nutrition into its second phase (2016–2020), with commitments to school-based IFA supplementation, nutrition counselling, and the integration of adolescent nutrition indicators into the Health Management Information System. Gebremedhin’s anaemia study illustrates both the burden and the dietary determinants in Ethiopian adolescents, noting that households in the lowest dietary diversity quintile faced an odds ratio for anaemia of 2.3 compared with the most diverse-diet quintile.¹ Progress has been documented but remains partial, constrained by geographic accessibility, teacher training gaps, and periodic supply disruptions.

Ghana occupies a middle-income SSA position with a more developed institutional infrastructure but significant north-south inequity. The Northern, Upper East, and Upper West regions of Ghana bear a disproportionate share of adolescent stunting and anaemia burden, reflecting both dietary poverty and the historically lower reach of formal education and health services in these areas. Ghana’s national adolescent health strategy (2017–2021) included commitments to expanding school-based nutrition services and strengthening community adolescent responsive care, with monitoring through the Ghana Health Service district information system - an infrastructure whose conceptual architecture is explored in the evolution of public health monitoring frameworks that have shaped similar systems across the continent.

Nigeria, with its scale and internal diversity, presents the most complex programming environment. With a population exceeding 220 million and an adolescent cohort estimated at 40 million, even modest improvements in programme coverage generate substantial absolute burden reduction. The Federal Ministry of Health’s 2021–2025 National Adolescent Health Strategic Plan identifies anaemia, undernutrition, and teenage pregnancy as priority concerns, but programme implementation remains heavily dependent on state-level capacity and political will. In Kano, Sokoto, and Zamfara states - where adolescent girl anaemia prevalence exceeds 50% in some surveys - formal school-based supplementation programmes have limited reach given out-of-school rates of 40–60% among adolescent girls in these regions.

Limitations and Methodological Considerations

Research on adolescent nutrition in SSA is characterised by a persistent gap between the depth of evidence available for under-five populations and the relatively sparse data for adolescents aged 10–19. Several methodological limitations constrain the current evidence base and deserve explicit acknowledgement.

First, the majority of nationally representative nutritional surveys in SSA - including Demographic and Health Surveys and Multiple Indicator Cluster Surveys - have historically concentrated their biomarker components on children under five and women of reproductive age (15–49). Adolescent-specific haemoglobin, ferritin, and zinc data are rarely collected systematically, meaning that prevalence estimates for adolescent micronutrient deficiency frequently rely on extrapolation from adjacent age groups or from smaller, non-representative studies. The Gebremedhin Ethiopia study is a useful exception, but its design is cross-sectional and limited to a single sub-national context.¹

Second, dietary assessment methodology in adolescent populations presents specific challenges. Twenty-four-hour dietary recalls, the predominant assessment tool, are subject to recall bias that may be more pronounced in adolescents than in adult respondents; portion size estimation is less standardised in SSA food environments; and the frequent out-of-home eating patterns of adolescents - including school canteen meals and street foods - are poorly captured by household-based dietary assessment instruments.

Third, intervention trials targeting adolescent nutrition in SSA are small in number, short in follow-up duration, and frequently underpowered for detecting effects on biological endpoints beyond haemoglobin. The evidence for calcium supplementation, zinc supplementation, and multi-micronutrient supplementation in SSA adolescents specifically is insufficient to support strong clinical recommendations, despite plausible biological mechanisms and positive findings in South Asian trials. Victora and colleagues’ call for life-course cohort approaches that follow adolescents into adulthood remains largely unheeded in SSA research funding architectures.³

Fourth, male adolescents are systematically under-studied relative to their female counterparts. The focus on girls - justified by reproductive health concerns and higher anaemia prevalence - has produced a blind spot with respect to iron deficiency, zinc deficiency, and stunting among adolescent boys, whose nutritional needs during peak growth velocity are substantial and whose engagement with formal health services is generally lower.

These gaps are not merely academic. They impede the development of adolescent-specific dietary reference values calibrated to SSA dietary contexts, the design of sex- and age-disaggregated supplementation protocols, and the construction of monitoring systems capable of tracking progress towards adolescent nutrition targets with the fidelity applied to under-five stunting and wasting.

Frequently Asked Questions

What are the primary nutritional needs of adolescents that differ from adults?

Adolescents have substantially higher requirements for energy, protein, iron, calcium, and zinc relative to body weight compared with adults, driven by the energetic and substrate demands of pubertal growth, bone mineralisation, and lean mass accretion. Adolescent girls have additionally elevated iron requirements due to menstrual blood loss, and folate requirements are high across both sexes due to rapid cell division. These needs peak during the growth spurt - typically ages 11–13 for girls and 13–15 for boys - and remain elevated until linear growth is complete.

What is the “second window of opportunity” in the context of adolescent nutrition?

The “second window of opportunity” refers to the period of developmental plasticity during adolescence, during which nutritional interventions can partially compensate for deficits established in early childhood and significantly influence adult bone density, cognitive function, reproductive health, and productivity. It follows the “first 1,000 days” window (conception to age two) and is defined by its biological specificity: the window is time-limited, closing as pubertal growth completes and bone mineralisation reaches its peak.

Which SSA countries face the greatest burden of adolescent nutritional deficiency?

The countries with the highest documented burden include Ethiopia, Nigeria, Mali, Niger, and the Democratic Republic of Congo, where the convergence of dietary poverty, high adolescent pregnancy rates, early marriage, and limited school-based programme coverage creates acute risk. Within these countries, geographic variation is substantial: northern Nigeria, highland Ethiopia, and northern Ghana consistently show the highest anaemia and stunting prevalence among adolescent populations.

What interventions have the strongest evidence base for improving adolescent nutrition in SSA?

Weekly iron and folic acid supplementation for adolescent girls in school-based settings has the strongest evidence base and cost-effectiveness profile. School feeding programmes that include diversified, nutrient-rich foods show consistent benefits for dietary intake and attendance. Nutrition education and life skills programming, while less directly impactful on biomarkers in isolation, strengthens the enabling conditions for sustained dietary behaviour change. The greatest gains are likely to be achieved through integrated approaches that combine supplementation, food-based strategies, and structural interventions addressing early marriage and school dropout.