Garden-based interventions and early childhood health: a protocol for an umbrella review

Garden-based interventions have the potential to improve a wide range of child health outcomes, including enhancing dietary intake, increasing outdoor physical activity, diversifying the gut microbiome, and promoting general wellbeing. This may be due, in part, to the potential of garden-based interventions to promote healthy eating and physical activity, while enriching children with food origin and food systems knowledge [1‐3]. Research on garden-based interventions in youth and adult populations have shown associations between gardening and reductions in anger, stress, anxiety, and body mass index (BMI). They have also demonstrated improvements in cognitive functioning, life satisfaction, mood, and overall quality of life [4‐7]. There is growing evidence that garden-based interventions may have additional benefits for young children, such as stress reduction and improved mental health and academic performance, suggesting interventions which are garden-based may be able to improve multiple aspects of health simultaneously [5, 8]. However, previous systematic reviews have primarily focused on single health outcomes [9‐12], leaving large gaps in what is known about the holistic health and wellbeing impacts of gardening programs for young children.

Prior garden-based intervention studies in young children have found some improvement in dietary outcomes, such as fruit or vegetable intake, willingness to try new foods, and even BMI [13‐15]. Younger children may be more willing to taste and accept novel foods than older children [16], and exposure to fruits and vegetables by age 5 years is vital for establishing habitual consumption later in life [17]. Previous research has also shown that hands-on experiences through garden-based interventions may increase fruit and vegetable consumption more than an intervention that merely increases availability [3, 18]. Additionally, garden-based interventions have been utilized as a form of therapy for an array of disorders and diseases, such as autism spectrum disorder [19] and childhood cancer [20]. The benefits of improved dietary and physical activity behaviors and increased nutrition knowledge acquired from these interventions may have the potential to seep through into other child health outcomes, such as enhanced academic performance and improved mental health [10, 21]. However, few review articles have considered and assessed diverse child health outcomes within the same article

While a number of systematic reviews on garden-based interventions for children exist [5, 6, 8, 10, 11, 22‐24], there has yet to be a comprehensive umbrella review that summarizes the wide array of health benefits of garden-based interventions for young children. As noted above, existing systematic reviews on garden-based interventions for children focus primarily on single health outcomes, such as fruit and vegetable intake [11] or academic performance [10]. Additionally, most reviews examined only one type of gardening program (e.g., farm-to-preschool) rather than exploring the multiple settings in which garden-based interventions can be implemented [24]. Although there is a published review that looks more broadly at the health impacts of gardening in school-aged children, it included only one study with preschool-aged children [8]. Additionally, due to the diversity in settings, types, and benefits of garden-based interventions, we aim to holistically evaluate and summarize existing systematic reviews on garden-based interventions and health outcomes for young children in a single umbrella review.

The following question will guide this umbrella review: What role can garden-based interventions play in health promotion for children aged 6 years and younger? To successfully answer this question, we will explore the following objectives:

For included studies, we will report on confidence in findings using the information presented in each review. This could be in the form of a quality of evidence tool, such as the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) measures [31]. However, there are many additional tools that existing reviews can use to assess the confidence in evidence, which may cause variations in how this aspect is reported in reviews. As such, we will report on the exact tool used for included reviews and their associated findings, iteratively making the decision on how to display confidence in findings based on the information reported in each individual review. If a review is included in which the authors did not conduct an assessment of confidence in evidence, the review team will not conduct any de novo assessments. In this instance, there will be no confidence in evidence presented for that review.

For this umbrella review, we will report a summary of findings from all included reviews based on data synthesis, presenting a comprehensive overview of what is known in the literature on the role of garden-based interventions in health promotion for children aged 6 years and younger. We will create the summary of findings tables from extracted data, directly mapping findings to our research questions per the Joanna Briggs Institute methodology for conducting an umbrella review [25] and the Cochrane Handbook’s Methodology for conducting an overview of reviews [32]. We will take a mixed-methods approach to synthesizing the review literature, utilizing both qualitative methods (e.g., narrative synthesis) and quantitative methods (e.g., numerical patterns or associations). In line with the research questions guiding this umbrella review, we plan to highlight the strengths and weakness of included systematic reviews, as well as describe any evidence gaps we identify. We also plan to report on effectiveness of garden-based interventions. For this, we will present a grid of intervention components and child health and well-being outcomes, noting directionality of each outcome. We plan to summarize the setting, outcome measures, numbers of children, and pooled results from each review, including implications for future research and practice through tables and narration, as appropriate. When reporting findings in tabular form, we will present child health outcomes across included reviews, stratifying tables by review methodology (e.g., all evidence gained from reviews of randomized controlled trials) and child health outcome (e.g., reporting evidence on academic performance separately from nutrition outcomes). For child health outcomes, we anticipate reporting tabular results in the following categories: child nutrition outcomes, academic performance, education, mental health and social skills, gut microbiome, and physical activity. For child nutrition outcomes, we anticipate a need to break down results further, in which case we will report results in the following categories: (1) intake, reporting separately on fruit and vegetable intake as allowed; (2) selection, reporting fruit and/or vegetable selection and preference outcomes; and (3) biometric and anthropometric outcomes (e.g., body mass index, wasting, etc.) Where tabular presentations of results are presented, they will be accompanied by detailed descriptions. As we are including a broad range of health outcomes, we expect included reviews to report on child health outcomes in different ways and will be limited to what is reported. We will aim to report health outcomes stratified by the following age groups: infancy (less than 12 months of age), toddlers (12 months of age–less than 36 months of age), and preschool (3 years of age–less than 6 years of age). However, we will be limited in this stratification by how included reviews report on health outcomes by age. For example, if a review stratifies findings by age (e.g., preschool, school-age), we will report our results accordingly. Similarly, if a review does not separate results by age, we will only be able to report what is reported in the review. In this instance, results that cannot be disaggregated by age will be reported separately within our review.

Additionally, we will create a table summarizing the AMSTAR 2 results for each included review. As is best practice, we will report the entire umbrella review in accordance with PRISMA guidelines.

Due to the potential for overlap of primary studies in the review articles, we will report the number of times individual studies are included across multiple reviews. We will systematically identify any occurrences of overlap across systematic reviews by noting individual studies included in more than one review. We will also explore the consistency of reporting at the individual level across reviews [33] to determine if there is any overlap. We will explore this through the use of The Cochrane Handbook’s template for mapping individual primary studies contained within included systematic reviews [32]. For example, one review article may report on one specific child health outcome of an individual study, while another review includes the same study but reports on a different (perhaps secondary) health outcome. In this case, we would not consider this overlap. However, if reviews are reporting the same outcomes from the same study, we will highlight this overlap. If we do find there is overlap, we will calculate the corrected covered area [34] and report on this measure in the review paper. We will also consider overlap when interpreting results of the review.

For this umbrella review, we aim to (1) identify and synthesize existing review and meta-analysis articles on garden-based interventions for young children; (2) identify the most prominent measures used to detect and assess the impacts of garden-based interventions in young children; (3) critically evaluate the available evidence both narratively and quantitatively; and (4) identify gaps in the literature and describe areas of improvement for the scientific field of garden-based interventions, including, but not limited to study design, measurement, and child health outcomes. In doing so, we will provide a very comprehensive overview of what is known in the literature about the health and wellbeing impacts of gardening programs for young children.

This umbrella review has several strengths. First, this umbrella review fills a considerable gap in the literature by providing a holistic overview of existing evidence of the health and wellbeing benefits of garden-based interventions for young children, identifying strengths of current evidence and highlighting areas for improvement. To date, this type of umbrella review does not exist. Second, this review will examine knowledge gaps in the field and elaborate on how these gaps could be addressed by future research. Summarizing this information will be an asset to both researchers and public health professionals aiming to improve the health and wellbeing of young children. Additionally, this umbrella review will be conducted using the most systematic procedures available at this time. Adhering to these guidelines helps ensure that we procedure a high-quality umbrella review that will be a useful and trusted resource for interested parties.

Anticipated challenges for this review include the need to extract relevant information from existing review articles. We realize there are numerous benefits to garden-based interventions throughout the life span. However, we only focused on children younger than 6 years, as this is an area where garden-based interventions in an ECE, community, or home setting could make a substantial impact. We limited our search to peer-reviewed literature published after 1990, but do not believe this will exclude any relevant studies based on the pilot search strategy. However, we realize the exclusion of non-peer reviewed literature may eliminate high-quality reviews, which is another limitation. We will elaborate on additional limitations in regard to findings in the narration of the review. Another limitation of this review will be the potential for study overlap across reviews. Knowing this potential risk, we will examine and report on any overlap in the review.

Despite anticipated limitations, conducting this umbrella review on the role of gardening for health promotion in young children could be of great importance for researchers, public health professionals, and policymakers. By summarizing the current evidence for and simultaneously identifying strengths, weaknesses, and limitations for garden-based interventions, we hope to strengthen the quality of future research in this area. Further, we hope to support and highlight evidence-based interventions that improve the health and wellbeing of young children.