Adequate nutrition is fundamental to optimal physical and cognitive growth in the second year of life. Toddlers, however, are particularly vulnerable to poor nutrition due to their high nutrient needs in relation to their body size and energy intakes. Nutrient-dense diets are therefore essential during this period. However, no practical quantitative food-based dietary guidelines directed at this age group are available to help caregivers choose nutrient-rich foods for their toddler. Such guidelines are needed not only to ensure adequate intakes of all nutrients during the period of dietary transition from infant to family foods, but also to emphasise intakes of nutrients for which toddlers are at particular risk of deficiency. Biochemical evidence suggests that iron nutrition requires special attention in New Zealand toddlers. The overall aim of this thesis was to design and assess the efficacy of practical food-based strategies for toddlers to ensure optimal nutritional status of 12-24 month old New Zealand children, with a specific focus on iron nutrition. To achieve these overall aims, the research was carried out in three stages.
In the first stage, secondary data analysis of food intake data for New Zealand toddlers identified the foods commonly consumed by New Zealand toddlers, the serving sizes and frequency of consumption of these foods, and the nutrients that New Zealand toddlers are at risk of consuming in suboptimal amounts. The food intake data were obtained from 3-day weighed food intakes that had been collected on non-consecutive days in an earlier community-based cross-sectional survey of 188 randomly selected non-breastfeeding 12-24 month old urban South Island New Zealand children. In addition to describing the food consumption patterns of New Zealand toddlers, the secondary data analysis also identified that nearly 40% of New Zealand toddlers were at risk of suboptimal iron intakes.
The results of these analyses were used in the second stage of the thesis to develop three food-based strategies. To do this a 4-phase approach based on linear and goal programming was used to design and hypothetically evaluate three sets of food-based strategies for 12-24 month old non-breastfeeding New Zealand children, and to identify the key problem nutrients for each set of strategies. The three sets of strategies were based on: (1) all foods consumed by toddlers including iron-fortified infant and toddler foods, (2) family foods only, or (3) family foods that are not fortified with iron. The mathematical modelling confirmed that iron was the key problem nutrient in the diets of New Zealand toddlers. The analysis showed that only food-based strategies that included a recommendation for the replacement of non-fortified cow�s milk with an iron-fortified toddler milk (500 mL), i.e. strategy set 1, achieved the Australian-New Zealand Recommended Dietary Intakes for all nutrients, including iron. In fact, inclusion of a recommendation for a substantially increased consumption of flesh foods was identified as the only possible alternative to the iron-fortified toddler milk recommendation for improving iron nutrition in New Zealand toddlers. Although the set of strategies including this flesh food recommendation did not provide as much total iron as those including the iron-fortified toddler milk recommendation, the bioavailability of the iron is likely to be greater because flesh foods provide highly bioavailable haem iron (red meat being a particularly rich source) and have an enhancing effect on the absorption of non-haem iron. The two key recommendations for achieving New Zealand toddlers� iron needs were, therefore, a recommendation to consume an iron-fortified toddler milk and a recommendation to consume substantial amounts of red meat.
In the third stage, the efficacy of an increased intake of red meat or the use of an iron-fortified milk for improving biochemical iron status in healthy non-anaemic 12-20 month old New Zealand children was investigated in a 20-week partial double-blind randomised placebo-controlled intervention trial. The study also examined the effect of these two interventions on dietary iron intakes and growth, and investigated the association between the amount of meat consumed and biochemical iron parameters. Participants (n=225) were assigned to one of three groups: Meat Group (n=90), Fortified Milk Group (n=45), or Placebo Group (n=90). Children in the Meat Group were encouraged to consume two red meat dishes per day (~ 2.6 mg of iron). In the Fortified Milk Group and Placebo Group, the children�s regular milk was replaced with iron-fortified cow�s milk (1.5 mg of iron per 100 g of prepared milk), or non-fortified cow�s milk (< 0.1 mg of iron per 100 g of prepared milk), respectively. Geometric mean dietary iron intakes (95% CI) increased from 4.7 (4.1, 5.3) to 5.3 (4.7, 6.0) mg per day in the Meat Group (P=0.007), and from 4.3 (3.7, 5.0) to 10.4 (9.0, 12.2) mg per day in the Fortified Milk Group (P<0.001). These increased iron intakes differed significantly from the Placebo Group (both P<0.001), which declined from 5.1 (4.5, 5.7) to 4.6 (4.1, 5.2) mg per day during the intervention (P=0.047). Over 20 weeks, adjusted geometric mean serum ferritin concentration increased by 44% (95% CI: 14%, 82%) in the Fortified Milk Group (P=0.002), tended to decrease in the Placebo Group (14% decrease (95% CI: -27%, 1%; P=0.063)), and did not significantly change in the Meat Group (10% increase (95% CI: -7%, 30%; P=0.241)). However, because iron status declined in the Placebo Group, both groups fared significantly better than the Placebo Group: serum ferritin concentration at 20 weeks was 68% (95% CI: 27%, 124%; P<0.001) greater in the Fortified Milk Group than in the Placebo Group, and 29% (95% CI: 2%, 63%; P=0.033) greater in the Meat Group than in the Placebo Group. There were no intervention effects on haemoglobin or serum transferrin receptor concentration. The cross-sectional analysis showed that a daily intake of 1 g of red meat was associated with 0.65% (95% CI: 0.18%, 1.11%; P=0.007) higher serum ferritin concentration. No adverse effects of the interventions on the toddlers� growth were detected.
In conclusion, this thesis shows that food-based strategies can be designed that, if adhered to, should ensure adequate iron status in New Zealand toddlers. Although both the iron-fortified milk recommendation and the increased red meat recommendation are likely to prevent the decline in body iron stores that can occur during the second year of life, only consumption of iron-fortified milk can successfully increase iron stores. Therefore, food-based strategies for New Zealand toddlers will need to include a recommendation that encourages the consumption of foods developed specifically for toddlers that are fortified with iron.
| Identifer | oai:union.ndltd.org:ADTP/217867 |
| Date | January 1900 |
| Creators | Szymlek-Gay, Ewa Anna, n/a |
| Publisher | University of Otago. Department of Human Nutrition |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Ewa Anna Szymlek-Gay |
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