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Effects of iron fortification ...

TABLE 3. Haematological and iron status at baseline, changes from baseline to the end of intervention, and changes from baseline to five months after intervention in children with adequate baseline iron stores

See table 2 for abbreviations.

Values are means and (SD).

TABLE 4. Anthropometric measurements at baseline, changes from baseline to the end of intervention, and changes from baseline to five months after intervention in children with adequate baseline iron stores

See table 2 for abbreviations.

Values are means and (SD).

Table 4 shows the anthropometric results at baseline, the changes from baseline to the end of the intervention, and the changes from baseline to five months after the intervention in children with low baseline iron stores. Anthelmintic therapy was associated with greater increases in height (p=.0015) and height-for-age Z scores (p=.0027) compared with a placebo. Significant interaction between iron fortification and anthelmintic therapy was observed for height (p = .0263), height-for-age Z scores (p = .0154), and weight-for-height Z scores (p=.0087). Five months after the intervention, the children who were treated had greater increases in height (p= .0344) and weight (p=.0346) than those who received the placebo.

In table 5 the anthropometric results at baseline, the changes from baseline to the end of the intervention, and the changes from baseline to five months after the intervention in children with adequate baseline iron stores are given. Neither anthelmintic therapy nor iron fortification alone was associated with significant effects on these parameters. Significant interaction between these two interventions for weight (p = .0208) and weight-forage Z scores (p = .0262) was observed during and after the intervention (p = .0099 and .0115, respectively).

Parasitic infections were found in 58.7% (91/155) of the children. Height-for-age Z scores at baseline were lower (p = .0018) in children with parasitic infections (n = 91; -1.35 ± 0.87) than in those without infection (n = 64; -0.88 ± 0.88). Trichuris trichiura, Ascaris lumbricoides, and Hymenolepis nana were the most common parasitic species at baseline in this population, with prevalences of 38.1% (59/155), 20.0% (31/155), and 20.7% (32/155), respectively. At baseline 33.9% of the 59 children infected with T. trichiura were anaemic, compared with 9.4% of the 32 infected with parasites other than Trichuris. Hb concentrations tended to be lower in children with Trichuris infection (12.0 ± 0.9 g/dl vs 12.4 ±0.7 g/dl, p = .0541). The MCH (26.7 ± 1.6 pg vs 27.4 ± 1.3 pa, p = .0245), MCH concentration (32.1 ± 0.9% vs 32.7 ± 0.7%, p = .0004), and serum iron concentration (10.8 ± 5.1 mg/dl vs 13.0 ± 5.6 mg/dl, p = .0462) were lower and RDW (13.4 ± 1.0 µm vs 12.8 ± 0.6 µm, p = .0013) was higher in children with Trichuris infection compared with those infected with other parasites.

The prevalence of infection with more than one parasitic species decreased from baseline to the end of intervention in the groups that received anthelmintic treatment: FeA 15.9% (7/44) to 4.9% (2/41), and BA 31.4% (11/35) to 8.6% (3/35). It remained high in the placebo groups: FeP 12.5% (6/48) to 17.0% (8/47), and BP 39.3% (11/28) to 32.3% (10/31).

TABLE 5. Anthropometric measurements at baseline, changes from baseline to the end of intervention, and changes from baseline to five months after intervention in children with adequate baseline iron stores

See table 2 for abbreviations.

Values are means and (SD).

Figure 1 shows the effect of intervention on the prevalence of the three most common parasites in the 134 children with complete parasitological data. The prevalence of T. trichiura tended to decrease in all groups during the study period. The prevalence of A. Iumbricoides decreased in the FeA and BA groups during intervention compared with the FeP and BP groups. In the anthelmintic therapy groups, the prevalence of Ascaris increased again after intervention to nearly baseline values. The prevalence of H. nana decreased in the FeA group but increased in the BA group during intervention. The prevalences of Giardia lamblia (3.9%, 6/155), Enterobius vermicularis (1.9%, 3/155), and hookworm (1.3%, 2/155) were low at baseline and remained below 5% throughout the study.

Of the three most common parasites, only A. Iumbricoides showed significant treatment effects. Table 6 gives the analysis of weighted least-squares estimates for changes in the prevalence of this parasite from baseline to the end of intervention and for changes from the end of intervention to five months after intervention. Anthelmintic therapy significantly reduced the prevalence of Ascaris during intervention (p = .0226), but with cessation of therapy after the intervention the prevalence increased significantly (R = .0124).

A significant improvement in school attendance was associated with iron fortification (p= .0276) in children with low baseline iron stores. The percentage of days that these children were absent during the intervention period was 2.8% and 2.0% for the FeA and FeP groups, and 4.4% and 4.8% for the BA and BP groups, respectively. In children with adequate iron stores, the percentage days of absence was 2.2%, 3.5%, 3.5%, and 4.2% for the FeA, FeP, BA, and BP groups, respectively, during the intervention. After the intervention, the rates of absenteeism were similar for all the groups.

Discussion

Baseline status

The high prevalence of anaemia of 42.5% according to WHO criteria, which we observed in children age 6 to 8 years, is in agreement with that estimated for ages 5 to 12 years in Africa (49%) [21]. These prevalences were higher than the 6% to 18% reported for 6- to 11-year-olds of mixed ethnic origin in other areas of the Cape Province [7, 22]. Iron deficiency, as indicated by high prevalences of low serum ferritin (15.6% < 10 µg/L) and low transferrin saturation (25.7% <11%), was the major cause of anaemia in the present study. The finding of significantly lower heights and height-for-age Z scores in children with low iron stores adds to the evidence of the inhibiting effect micronutrient deficiencies have on growth [23, 24].

Our results indicated that the high prevalence of parasitic infections (58.7%) probably also contributed to the prevalence of stunting, underweight, and iron deficiency in these children, probably due to malabsorption, diarrhoea, and blood loss [25]. This was confirmed by the finding that these children had lower height-for-age Z scores than children without infection. Infection with T. trichiura, the most common parasite in these children, was associated with higher prevalences of anaemia and hypochromia (indicating iron deficiency), similar to that described during intense Trichurts infections (10,000 eggs/g stool) [26]. Daily iron losses may reach more than 1 mg in severe Trichuris infections [27]. In the present study hookworm infection was not common.

Effect of iron fortification

Iron-fortified soup providing 18.4 mg elemental iron or 0.9 mg absorbable iron per school day was associated with positive changes in Hb, MCV, and serum ferritin after the intervention. The effect was greater in children with low baseline iron stores than in those with adequate iron stores. Five months after the intervention, the positive effect of iron fortification on serum ferritin was still significant in children with low baseline iron stores.

In a pilot study with the same fortified soup, significant improvements in serum ferritin, but not in Hb, were observed within four months [12]. That intervention period may have been too short, however, since iron status does not change as rapidly with fortification as it does with supplementation [28]. In a trial in Chile using Hb-fortified chocolate biscuits (providing 1 mg absorbable iron) in a school feeding scheme, improvement in Hb was observed after 15 months [10]. In studies in which iron supplementation with higher doses (32-56 mg elemental iron/ day) was given to schoolchildren, haematological and iron status values improved within two to four months [4, 5,11].

Transferrin saturation increased equally in all treatment groups during intervention. Possibly a decrease in the rate of viral and bacterial infections (indicated by the lower white cell counts) had a greater effect on transferrin saturation than the additional iron intake. The post-intervention survey was conducted during summer, when the prevalence of infection tends to be low. Infection and iron deficiency are both associated with decreased transferrin saturation, but they have opposite effects on TIBC; infection is associated with decreased, and iron deficiency with increased, TIBC [29].

FIG. 1. The prevalences of Trichuris trichiura, Ascaris lumbricoides, and Hymenolepis nana in six- to eight-year-old schoolchildren before, during, and after intervention. Anthelmintic therapy: solid line with dots = iron-fortified soup; broken line with dots = unfortified soup. Placebo: solid line with stars = iron-fortified soup; broken line with stars = unfortified soup

In children with low baseline iron stores who received iron fortification, TIBC tended to decrease, indicating improved iron status, whereas in those who received unfortified soup, it tended to increase. In a population where infection is common, it is advisable to use transferrin saturation in combination with TIBC to evaluate iron status [29].

Iron fortification alone did not have a significant effect on growth or weight gain in this study. Studies in Indonesia [30] and Kenya [31] showed positive effects of iron supplementation on weight gain in deficient children. In the Indonesian study, iron supplementation was also associated with faster growth in anaemic children compared with a control group [30]. Interventions with single nutrients produced conflicting results concerning their ability to reduce stunting. Possible explanations for this are the existence of several growth-limiting nutrient deficiencies in the same children, and different study periods, doses of iron, and degrees of iron deficiency [23]. In contrast to the findings of another group [32], we did not observe a negative effect of additional iron on weight gain in children with adequate iron stores. This lack of a negative effect may be due to the lower dose of iron used ( + 1 mg/kg/day vs 3 mg/kg/ day) or the greater age of the children (6-8 yr vs 12-18 mo).

The decrease in absenteeism with iron fortification in children with low baseline iron stores is significant, because school attendance affects school achievement. A possible reason for this decrease is the lower rates of viral and bacterial infections. Much controversy exists regarding the effect of iron deficiency on infection. However, abnormalities in cell-mediated immunity, neutrophil function, and secretory response of macrophages were found in the presence of iron deficiency [33].

Effect of anthelmintic therapy

The prevalence of Trichuris infection decreased in the groups that received anthelmintic therapy; however, a larger dose or follow-up treatment may be necessary to eradicate this parasite. The treatment was very effective in decreasing the prevalence of Ascaris. Reinfection of treated children with Ascaris to the baseline level occurred within five months, which is in agreement with the reinfection rate (6-8 mo) reported earlier [34]. Regular fourmonthly anthelmintic treatment, as was given in the intervention period of the present study, decreased the prevalence of Ascaris effectively, whereas six-monthly treatments reduced the intensity (worm load), but not the prevalence of parasitic infections [35].

The association between anthelmintic therapy and Hb in children with low baseline iron stores was significant and was reasonably assumed to be due to the reduction in Trichuris infection.

TABLE 6. Analysis of weighted least-squares estimates for the effects of anthelmintic therapy (A), iron fortification (Fe), and time, and their interactions on the prevalence of Ascaris lumbricoides

Other studies of worm treatment that positively affected Hb and iron status were mostly in communities with a high prevalence of hookworm infection [2,11].

Children with low baseline iron stores experienced improved growth after anthelmintic therapy. Five months after intervention, their weight gain was also significantly improved. This is in agreement with the reported positive effect of anthelmintic treatment on weight gain [36-38] and growth [38]. These positive effects can be expected with reduction in diarrhoea, anorexia, malabsorption, and iron loss caused by parasitic infections [25].

Effect of a combination of Iron fortification and anthelmintic therapy

Significant combined effects of iron fortification and anthelmintic therapy, over and above the effect of each treatment alone, were observed in MCH and iron status in children with low baseline iron stores. In populations in which parasitic infections are common, increased iron intake has a limited effect on the improvement of anaemia if it is not combined with deworming [2, 28].

Height and Z scores for height-for-age and weightforheight increased significantly more in children with low baseline iron stores when the two treatments were combined. Although iron fortification alone did not have a significant effect on linear growth, it enhanced the effect of anthelmintic therapy in these children. This adds to the evidence that iron deficiency was a limiting factor in their growth. In children with adequate iron stores, in whom iron deficiency was probably not a limiting factor for growth, the combined treatment resulted in improvements in weight and weight-for-age Z scores.

Conclusion

This study showed that iron deficiency, parasitic infections, and possibly stunting in school-age children can be addressed effectively with iron fortification of soup in a school feeding scheme combined with regular anthelmintic therapy. Decreases in the prevalence of iron deficiency and parasitic infections improve not only children's physical well-being, but probably also their ability to learn [39]. School feeding schemes for iron fortification have the benefits of a regulated intake of the fortified food (preventing excessive intakes of the fortificant), and the targeting of age groups in which iron deficiency has been found [33].

Acknowledgements

The authors gratefully acknowledge the cooperation of the Peninsula School Feeding Association; the kindness and cooperation of the principals, staff, and children in the Esselen Park, Rabie, Rawsonville, Roodewal, and Victoria Park Primary schools; all those who prepared the school feeding during the study; Mr. C. Woodroof, Mr. DeW. Marais, and Mrs. M. Marais for laboratory assistance; and Miss M. Faber, Dr. M. Weight, Mr. G. Engelbrecht, and Miss J. Van Wyk for assisting with the fieldwork. We thank Funa Foods for the fortified and unfortified soup for the five schools during the intervention period; SmithKline Beecham Pharmaceuticals (Pty) Ltd. for generously supplying the Zentel and the placebo; Dr. P. L. Jooste, Dr. A. Evans, and Dr. R. Gross for reviewing the manuscript; and the Medical Research Council for permission to publish.

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