Dietary intake in relation to iron status in 5-12 year old primary school children and estimated cost of a nutrient rich diet

Abstract

Background: Poor nutrition is one of the main causes of nutritional anaemia, with half of the cases estimated to be due to iron deficiency (ID). School-age children are at high risk of these nutritional disorders due to their increased nutrient requirements, accelerated physical and intellectual development, but poor dietary intake. It is generally accepted that individuals do not consume isolated foods or nutrients and that nutrients interact with each other and influence the bioavailability and absorption. There is a need to evaluate a diet as a whole and explain how the various nutrient combinations and foods from various food groups are related to the risk of developing nutritional anaemia in school-age children. Also, it is important to compare the nutrient density and cost of the diets of children according to their anaemia and iron status and to identify foods that provide the most dietary iron per unit cost. Aim and objectives: The aim of the study was to determine the relationship between dietary intake and iron status in three study groups of 5- to 12-year-old primary school children residing in the KwaZulu-Natal and North West provinces of South Africa. The objectives were to assess nutrient patterns and its relation to anaemia and iron status; to examine the association of dietary diversity with anaemia and iron status; and to investigate the relationship of nutrient density and cost of diet with anaemia and iron status in school children using pooled data from three study populations in South Africa. Methods: A pooled analysis was conducted with existing baseline data of 5- to 12-year-old primary school children (n = 578) derived from three independent intervention studies conducted in two provinces in South Africa. The following data were extracted from the databases: socio-demographic information; anthropometric measurements (height and weight); biochemical data haemoglobin (Hb), plasma ferritin (PF) adjusted for inflammation, C-reactive protein (CRP); and dietary intake data (energy, and macro- and micronutrients). Nutrient patterns were determined using factor analysis; dietary diversity scores (DDS) were calculated based on data from 1-day and 3-day reference recall periods on nine food groups consumed; and the nutrient density of foods and diets was calculated using the Nutrient Rich Foods Index (NRF9.3). The nutrient density-to-price ratio of foods and total diets was estimated by attaching food prices to the dietary intake data. Descriptive statistics, factor analysis, analysis of variance, analysis of covariance, and regression analyses were used to compare the study groups and to examine the associations of dietary intake with anaemia and ID status of studied children. Results: In the pooled group 13.8% of the children were anaemic and 27.7% were ID. More than half of the children did not meet the requirements for various nutrients, that is, vitamin A, vitamin C, vitamin B12, folate and zinc; however, 18% of children had an iron intake below the requirements. Four nutrient patterns were identified: ‘plant protein, carbohydrate, iron and B-vitamins’; ‘animal protein and saturated fat’; ‘vitamin A and vitamin B12’; and ‘calcium and fibre’. The ‘vitamin A and vitamin B12’ nutrient pattern was associated with lower odds of being anaemic [OR 0.63 (0.49-0.91), p = 0.035]. For both reference recall periods, consumption of ‘vegetables and fruits other than vitamin A-rich’ and ‘animal-source foods (ASF)’ was associated with lower odds of being anaemic (both p = 0.002); and ‘organ meats’ with lower odds of being ID (1-day p = 0.045; 3-day p < 0.001). Consumption of ‘meat and fish’ was associated with lower odds of being anaemic (p = 0.045) and ‘vegetables and fruits other than vitamin A-rich’, ‘legumes, nuts and seeds’ and ‘ASFs’ with lower odds of being ID for the 3-day recall period only (p = 0.038, p = 0.020; p = 0.003, respectively). A DDS ≤ 4 was associated with higher odds of being anaemic (1-day p = 0.001; 3-day p = 0.006) and being ID (3-day p < 0.001). Diet cost did not differ according to anaemia and ID status, although the nutrient density-to-price ratio was significantly lower for anaemic versus non-anaemic children (p = 0.001). Children with anaemia and ID had significantly lower NRD9.3 diet scores compared to non-anaemic and non-ID children. Conclusion: The combination of dietary vitamin A and vitamin B12 known as enhancers and facilitators of dietary iron absorption may play an important role in the aetiology of nutritional anaemia in school age children in South Africa. Dietary diversification and the importance of consuming vegetables, fruits and foods from animal sources should be considered. Selecting nutrient-dense foods in order to substitute foods with low nutrient density may be a promising way to consume a diet richer in specific nutrients, and may thus help to prevent nutritional anaemia and ID in South African school-age children without affecting the cost of the total diet