Effects of fish oil supplementation on learning and behaviour of children from Australian Indigenous remote community schools: A randomised controlled trial

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Abstract

Omega-3 fatty acids are essential for brain function. We recruited 409 children aged 3–13 years (M=8.27, SD=2.17) for a randomised controlled trial supplementing with placebo or fish oil capsules (providing 750 mg docosahexaenoic plus eicosapentaenoic acids, and 60 mg gamma linolenic acid/school day) for 20 school weeks (Phase 1) followed by one-way crossover to fish oil (Phase 2). Children undertook assessments of reading, spelling and non-verbal cognitive development (Draw-A-Person) at baseline, 20 and 40 weeks. Teachers completed Conners Behaviour Rating Scales (CBRS). The treatment group showed improvements in Draw-A-Person compared with the placebo during Phase 1 (p=0.029), with strongest effects in Indigenous 7–12 year olds (p=0.008). The placebo group showed significant within-group improvements after switching to treatment (p<0.001). There was no treatment effect for reading or spelling, and CBRS data were unable to be analysed. These findings may be understood in the context that sustained school attendance and nutrition interact to produce school-related achievement.

Introduction

Indigenous Australian children have significantly lower literacy and educational outcomes than non-Indigenous children [1]. Results from the National Assessment Program (NAP) indicate that the Northern Territory (NT) has the greatest discrepancy in academic outcomes, with 72.8% of total students, yet only 41.0% of its Indigenous students, reaching benchmark for reading. This pattern is consistent across measures of spelling and numeracy within the NT [2] and is even lower for students living in remote locations. This has wide-ranging implications for their ability to gain equality of access to occupational opportunities and impacts directly and indirectly on their developing sense of self-worth and ability to function effectively as members of a global community. Indeed, not only has education been identified as the largest predictor of employment outcomes for Indigenous Australians, but also of arrest rates [3], [4], and is likely to contribute to the disproportionately high incidence of incarceration in Indigenous populations [4], [5].

Factors that have been associated with educational outcomes for Indigenous children include parental education [6], school attendance rates, the quality of teaching, leadership and engagement with Indigenous culture, and language background. Predictors of educational achievement also include initial achievement and attentiveness [1]. It is likely that nutrition plays a significant role in the latter factors. Optimal nutrition is critical for healthy brain development and function [7], [8], [9] and Indigenous Australians and their children have a number of health problems largely associated with malnutrition [10], [11], [12], [13]. Not only does malnourishment impact on physical health, but is also associated with impaired cognitive function, thereby impacting on learning and behaviour [14], [15], [16], [17], [18].

Omega-3 polyunsaturated fatty acids (n-3 PUFA) are particularly important for brain development and function, especially docosahexaenoic acid (DHA) [19], [20], [21], [22]. Humans cannot synthesise PUFA, so we must consume them in our diet. Plant sources of the parent n-3 PUFA alpha linolenic acid (ALA) include dark leafy vegetables, nuts and seeds, and ALA can be elongated to the longer chain n-3 PUFAs EPA and DHA. These long-chain n-3 PUFAs can also be consumed directly in marine algae and oily fish. Traditional diets contained significantly higher levels of n-3 PUFA than current Western-style diets. Whereas the ratio of n-6 PUFA to n-3 PUFA was traditionally about 1:1, in modern diets it is estimated at 15–16:1 [23]. This is not only attributable to decreased n-3 PUFA intake but also to increased intake of vegetable oils, which currently predominate in cooking as well as processed foods. Accordingly, a recent national survey found that Australian children are consuming very little, if any, n-3 PUFA in their diets [24]. Suboptimal levels of n-3 PUFA, possibly in combination with higher n-6 PUFA levels, have been implicated in a range of mental health problems [25], [26], [27].

Among studies with n-3 PUFA and mental health, a small but growing body of researchers is finding improvements with supplementation on learning and behaviour in children [28], [29], [30], [31]. The strongest effects are seen in subgroups with behaviour problems and learning difficulties [28], [29], [32], although a recent study with healthy boys reported improved frontal lobe activation following DHA supplementation compared with placebo, and a significant association between erythrocyte DHA levels and better reaction time during a sustained attention task [33]. Three studies in particular, all performed with the same fish oil supplement, found improved ratings of behaviours associated with attention deficit hyperactivity disorder (ADHD), including hyperactivity and inattention in different groups of children [28], [29], [30]. One of these also reported significantly improved reading and spelling in their sample, who at baseline were on average a year behind [29], and another reported strongest effects, within their sample of children and adolescents with ADHD, in a subgroup with reading and writing difficulties [28]. We found lower erythrocyte DHA levels in children with ADHD who were functioning behind their age level in reading and spelling compared with children with ADHD and no learning difficulties [34] and improvements in reading, spelling and behaviour were associated with increased DHA levels over 4 months, particularly in the subgroup with learning difficulties [32].

We recently conducted an open-label pilot study to investigate the feasibility of providing fish oil supplements to children in a remote school in the Northern Territory (NT) with a high Indigenous population [35]. The supplementation quickly became a smooth part of the daily school routine, and teachers provided anecdotal reports of improved learning and behaviour. Within-group analyses indicated improved reading, spelling and problem solving ability. The present study followed this up with a randomised, placebo-controlled study with children in four Northern Territory (NT) primary schools with predominantly Indigenous attendance to investigate whether supplementation with fish oil improved literacy, non-verbal cognitive development and teacher reports of learning and behaviour compared with placebo.

Section snippets

Participants and procedure

All children with parental consent from participating schools were eligible to take part in the study; they were recruited from four schools with a total of 560 students. A minimum of 60 per group was required to achieve a medium effect size [36]; we aimed to maximise our sample size to allow for the large turnover of students and teachers that we identified in our pilot study. Year levels at the schools ranged from transition (reception) to year 7; one school included pre-school children, and

Data preparation

Data were not missing completely at random (MCAR). However, it was likely to be missing at random (MAR), and missing variables unlikely to be related to the intervention—mostly due to high student and staff turnover (e.g. one school had virtually a complete staff turnover between Phases 1 and 2 and subsequently discontinued the study). Therefore, it was determined that it was reasonable to conduct linear mixed modelling analysis. Checking of distributions revealed that the following variables

Discussion

In this school-based fish oil study we found significant improvements in the treatment group vs. placebo on cognitive development and not academic achievement as measured by either spelling or reading. Specifically, the treatment group showed improvements compared with placebo on Draw-A-Person (DAP), our non-verbal, culture-free assessment of cognitive development over 20 school weeks (Phase 1) and the placebo group then showed similar improvements after switching to fish oil for a further 20

Acknowledgements

N. Parletta (formerly Sinn) is supported by NHMRC Program Grant funding (Nos. #320860 and 631947). The authors gratefully acknowledge the assistance of Professor Peter Howe (chief investigator on the ARC-linkage grant), Professor Sven Silburn, Cheryl Edward, Donna Hughes and all research assistants, as well as the Northern Territory Department of Education and Training for their support, all school Principals, teachers and staff, parents and students for making this study possible. Our much

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    This project was funded by Australian Research Council Linkage grant LP1001008673 in partnership with Vifor Pharma.

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