Background

Iron deficiency anemia is recognized as the leading nutritional problem in adolescents, but there are few data available on prevalence in this population, estimated at 27% in developing countries and 6% in industrialized ones [1].

Adolescents constitute a risk group for iron deficiency and iron deficiency anemia, with important consequences for health, due to the period of rapid growth, increase in body mass, expansion of blood volume, and onset of menstrual loss in girls, associated with a poor diet [1, 2].

In Brazil, there have been no nationally representative studies that indicate the situation of iron deficiency and iron deficiency anemia during adolescence, and existing studies are scarce, punctual, and were performed with different methodologies in small and restricted samples. Regional studies have observed that the prevalence of anemia on both sex ranges from 6.4 to 41.7% [3,4,5,6,7,8], in females from 7.5 to 31.1% [4,5,6,7] and males from 6.0 to 31.4% [4,5,6]. The prevalence of iron deficiency on both sexes is 21.2% [3], in females 10.3% and in males 18.6% [9].

Since iron deficiency anemia is a major nutritional problem in Brazil with serious economic and social consequences and that wheat and maize flour are widely consumed by the Brazilian population, the National Health Surveillance Agency (ANVISA), by means of Resolution of the Board of Directors (RBD) No. 344, December 13, 2002, approved the technical regulation for the mandatory fortification of these flour types with iron and folic acid, in accordance with the recommendations from the World Health Organization (WHO) and the Pan American Health Organization (PAHO). According to the RBD, each 100 g of wheat or maize flour should contain at least 4.2 mg of iron and 150 μg of folic acid, which represent 30 and 37% of the recommended daily intake (RDI) for an adult individual, respectively [10]. The allowed iron compounds were dehydrate ferrous sulfate, ferrous fumarate, reduced iron, electrolytic iron, NaFeEDTA, and ferrous bisglycinate. The companies had 180 days to adjust their products, so the program started on June 2004.

Studies assessing the prevalence of iron deficiency anemia or iron deficiency in adolescents after the fortification of wheat and maize flours in Brazil have not yet been published. The National Survey of Demography and Health of Children and Women 2006 (PNDS) presented a positive national picture for the prevalence of anemia in children aged 6 to 59 months, 20.9%, when compared to studies conducted between 1990 and 2000, considering the flour fortification strategies as one of the hypotheses for this panorama [11]. However, Assuncao et al. [12] found no statistically significant difference in mean hemoglobin levels among children aged 0 to 5 years before and after flour fortification initiated in Brazil.

In view of the foregoing, the purpose of this study was to assess the iron nutritional status of adolescents, 6 years after the initiation of mandatory fortification of these flour types.

Methods

This is a historical control study conducted with adolescents aged 10 to 17 years, of both sexes, attended during the period from January to December 2010, at the Centro Saúde Escola Parque Capuava, a primary health care center, located on the outskirts of Santo André, Sao Paulo. Data were compared with the results of a previous study conducted at the same service in 2004 [9]. This study was approved by the Research Ethics Committee of the Federal University of Sao Paulo, with prior written consent from the adolescents and parents or guardians.

Exclusion criteria: pregnant adolescents and those who had recently given birth, patients with acute or chronic diseases, patients who had been transfused in the last 3 months, and patients in treatment with iron-based compositions.

Sampling: In 2004, the sample consisted of 255 adolescent records, with 129 being male. In 2010, data were collected from 934 patient records. After applying exclusion criteria, the final sample consisted of 697 adolescents, with 316 being male. For data collection, the most recent medical consultation to the biochemical assessment of iron status was considered. The possible comparison between 2004 and 2010 was on pubertal stage and transferrin saturation.

Anthropometric assessment consisted of weight and height measurements, according to WHO standards, 1995 [13].

Body mass index (BMI) was calculated by dividing the body weight (in kilograms) by the height (in meters), squared. For the classification of nutritional condition, Z-score graphs, according to age and gender from WHO, 2007, were used as standard reference [14].

Pubertal stages were assessed according to Tanner’s criteria, considering breast development in females and the development of external genitalia in males [15]. Information on age at menarche was also obtained from female patients.

Food consumption, collected from medical records, was assessed using the 24-h dietary recall method [16]. The diet was assessed on iron bioavailability, according to WHO, being classified as: low-bioavailability diet (simple, monotonous diet based on cereals, roots, or tubers, high in foods that inhibit iron absorption such as maize, beans, and whole wheat flour); intermediate-bioavailability diet (containing mainly cereals, roots, or tubers, with some foods of animal origin or sources of ascorbic acid); and high-bioavailability diet (diversified containing adequate amounts of meat, poultry, fish, or foods rich in ascorbic acid) [17].

Adolescents, at the center in question, are routinely submitted to a laboratory work-up, which includes a complete blood count, serum iron, transferrin saturation, serum ferritin, and parasitological tests.

Biochemical assessment: blood samples were collected according to standard technique and processed the same day for hemoglobin (Hb) assessment, using a hematology analyzer (ABX Pentra 120, HORIBA ABX Diagnostics, Inc., France). The amount of serum ferritin was determined using colorimetric method. Transferrin saturation was calculated by dividing the serum iron concentration by the total iron binding capacity (TIBC) multiplied by 100. Iron colorimetric assay kit (Ferrozine method) was used to determine serum iron and TIBC.

Iron deficiency was defined as the presence of alterations in at least two of the three biochemical laboratory parameters (serum ferritin <15 ng/dL; transferrin saturation index <16% for female and <20% for male; serum iron < 50 μg/dL). Anemia was defined as Hb concentration below the limits, 11.5 g/dL for children up to 11.9 years, 12 g/dL for girls above 12 years and boys aged 12 to 14.9 years, and 13 g/dL for boys aged 15 years and over. Iron deficiency anemia was considered as the sum of iron deficiency and anemia, as defined above [18].

The Mann-Whitney test was used to compare biochemical iron indices and the prevalence of anemia and iron deficiency, between sexes, of the adolescents assessed in 2010. The chi-square test was used to compare the frequencies of transferrin saturation between 2004 and 2010.

IBM SPSS (Statistical Package for Social Sciences), version 21.0, was used. Statistical significance was set at α < 0.05.

Results

Characteristics of the studied population in 2010 are provided in Table 1. BMI Z-score distribution in both sexes matched normal distribution according to the Gaussian curve, with seven girls and 11 boys being underweight, and 103 and 82 being overweight and obese, respectively. Mean Hb concentration is shown in Table 2 and serum ferritin, serum iron, and transferrin saturation index in Table 3, in which values were within the normal range for both genders.

Table 1 Characteristics of the studied population according to gender, 2010
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Table 2 Mean values of hemoglobin concentration of the studied population according to age and gender, 2010
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Table 3 Mean values of biochemical iron parameters of the studied population according to gender, 2010
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It was observed that 208/372 (55.9%) of female adolescents were in the post-growth spurt period, and 127/308 (41.2%) males were in the growth spurt period in 2010, and 162/255 (63.5%), with 105 (64.4%) male, and 57 (35.1%) female in the growth spurt in 2004 (Table 4).

Table 4 Pubertal stage (Marshall and Tanner [15]) of the studied population, 2004 and 2010
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In 2010, the prevalence of anemia was 1% (7/697), being 1.6% (6/381) in females and 0.3% (1/316) in males. The prevalence of iron deficiency was 3.2% (23/697), being 2.9% (11/381) in females and 3.5% (11/316) in males (Table 5).

Table 5 Prevalence of anemia and iron deficiency in the studied population according to gender, 2010
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Adolescents that consumed diets with low iron bioavailability constituted more than half of the sample, 52.7% (Table 6).

Table 6 Bioavailability of dietary iron (WHO [17]) consumed by the studied population, 2010
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The comparison of transferrin saturation values between 2004 and 2010 can be seen in Table 7.

Table 7 Frequency of iron deficiency in the studied population, according to transferrin saturation, 2004 and 2010
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Discussion

It must be pointed out in the Brazilian flour fortification that five compounds are permitted, most of them of poor bioavailability. Besides that, the monitoring of iron and folic acid in five mills in the municipality of Sao Paulo showed that 33% of the samples were satisfactory in 2005, 60% in 2006, and 80% in 2007. The Paulista Program with sampling in the retail trade of the State of Sao Paulo in 2006 reported 14% with iron content below the established minimum limit [19]. These facts make it difficult to evaluate iron consumption, making its quantification practically impossible. Only in 2012, the ANVISA established an Interinstitutional Commission for Implementation, Follow-up and Monitoring of the Fortification Actions of Wheat Flour, Maize and its By-products, through Ordinance No. 1793, which results are now in public consultation [20]. In spite of these facts, it was decided to evaluate the effect of this program, as it was carried out, on the nutritional status in adolescents.

Despite the majority of the adolescents being eutrophic, the number of overweight was higher than the number of underweight following the current nutritional transition in Brazil, as in other developing countries [21].

In adolescence, Hb levels are expected to be higher in males than in females because prostaglandins facilitate erythropoietic activity, both directly (PGE 1) and via cyclic AMP (PGE 2). Androgens stimulate erythropoietic activity through an increase in production or through facilitation in erythroid stem cells. Conversely, estrogens inhibit the effects of erythropoietin [3, 22]. It is expected, therefore, that Hb levels will increase with the evolution of pubertal stages in both genders. Until the age of 15, Hb differences between males and females are very discreet, widening thereafter (0.5 to 1 g/10 mL) due to increase in testosterone production and differences in sexual maturation [3, 22, 23].

In the primary health care center where this study was conducted, most of the adolescents are healthy, which demands are associated with psychosocial aspects, rhinitis, acne, and menstrual irregularities. Moreover, parasitological exams are required routinely and it is observed with an extremely low prevalence of parasitemia. That is why no biological markers of inflammation were required to adjust ferritin.

Six of the 11 boys (54.5%) with iron deficiency and the one with iron deficiency anemia were in the growth spurt period in Tanner stages 3 and 4, similar to that reported by Iuliano et al. [4] and Silva et al. [6]. In the whole group, the prevalence of iron deficiency anemia was 1.0%. This percentage is expected in this population, according to the WHO [18]. This value is far below those found in some regional studies conducted in Brazil [5, 7]. In 2004, the prevalence of iron deficiency was found to be 14.5% (37 individuals), of which 64.4% (24) were male, and 35.6% (13) female [9].

In this study, 6/12 adolescents with iron deficiency and 6/6 with iron deficiency anemia reported the occurrence of menarche, and 363 without iron deficiency or anemia also reported it. According to Lokeshwar et al. [24], between 25 and 50% of adolescents become anemic at the onset of menarche. In a study by Huang et al. [25], the highest percentage of iron deficiency and iron deficiency anemia in female adolescents was due to menstrual blood loss, with polymenorrhea (cycles with intervals of 21 days or fewer) being the main cause.

Iron deficiency is mainly due to the low consumption of foodstuffs with high iron bioavailability and the interaction of dietary components that impair iron absorption [2, 26]. In this study, all the adolescents with anemia and iron deficiency consumed diets with low or intermediate iron bioavailability. In a study conducted in Taiwan, most iron deficiency cases in males aged 10 to 18 years were attributed to inadequate food consumption [25]. Alaoèfe et al. [27] observed that the majority of girls that presented anemia and iron deficiency had low consumption frequency of meat, poultry, vegetables, and fruits. In the study by Borges et al. [26], children and adolescents that consumed low iron bioavailability diets had 1.68 times more likely (95% CI 1.10–2.56) of suffering anemia than those who consumed diets with high bioavailability of the nutrient.

In 2004, the prevalence of iron deficiency, based on low transferrin saturation, in females and males was 10.3 and 18.6%, respectively [9]. In 2010, this frequency decreased significantly, 4 and 10.4%, respectively.

Public policy adopted by the Brazilian government, which makes iron fortification of wheat and maize flour compulsory, may partially answer for the reduction in prevalence, in accordance with the PNDS 2006, since there was no important change for the Municipal Human Development Index (IDHM), between 2004 and 2010 [11]. Also, there were no programs aiming to increase iron bioavailability, and existing programs of iron supplementation is intended for pregnant women and adolescents in the municipality concerned, during this time.

The Brazilian studies show contradictory results in children and pregnant women. In a study conducted in Pelotas with children under 6 years old, there was no evidence of the effect of flour fortification on Hb levels, which remained constant, and the prevalence of anemia, contrary to what was expected, increased from 30.2 to 42.6% after 3 years of implementation of fortification [28]. However, Costa et al. [29] observed that 2 years after the implementation of fortification, the prevalence of anemia in preschool children attending the Early Childhood Education Centers in the municipality of Sao Paulo was 20.9%; a value significantly lower compared to the anemia rate of 63% in a previous study conducted in the same region.

In pregnant women at public services in the five geographic regions of Brazil, it was observed that after at least 1 year of the implementation of fortification, there was a decrease in the prevalence of anemia, with significantly higher mean Hb concentrations [30]. While in Maringa, although the frequency of anemia was slightly lower in pregnant women after mandatory fortification of flour compared to those before fortification, this difference was not statistically significant [31].

In Brazil, there are no studies on the impact of food fortification with iron in adolescents. In the urban area of southern Iran, Ramzi et al. [32] observed low prevalence of anemia (5.8%) and iron deficiency (8.5%) in female students aged 10 to 19 years, indicating a possible link to recent efforts by the government of that country to implement various projects to increase the absorption and bioavailability of iron through food fortification, supplementation, and promotion of greater food knowledge within the population.

Differently from the study by Martorell et al. [33] that evaluated in children and women the effect of iron fortification with ferrous fumarate and iron bisglycinate in Costa Rica, the present study presented the limitation of the impossibility of quantitative evaluation of iron consumption, as it was not known which of the iron compounds, and consequently its bioavailability, was used in the fortification. Thus, the consumption of iron was made qualitatively by the iron bioavailability of the diet, which in turn was calculated in a single recall of 24 h present in the medical records of adolescents, both in 2004 and in 2010. It was also not possible to compare between 2004 and 2010 the prevalence of anemia, due to the absence of this data in the 2004 records.

Conclusions

The Brazil results showed that anemia and iron deficiency are not prevalent in this population, probably due to the implementation of flour fortification with iron; it is not possible, however, to attribute such a result only to this strategy.