Abstract
Background: Diet quality in young children is low, with most children over-consuming refined grains, added sugars, sodium, and saturated fats, while simultaneously under-consuming whole grains, seafood, fatty acids, and fruits and vegetables (FVs). More specifically, in 2019, only 75% and 15% of preschoolers met the guidelines for fruits and vegetables, respectively. Despite the hundreds of studies conducted to address this low intake, several major gaps exist in this literature; there is a lack of studies conducted in a childcare setting that 1) objectively-measured dietary intake, 2) are informed by behavior change theory and the associated behavior change techniques, and 3) assess the known confounding variables that influence FV intake. Additionally, adult studies suggest a direct relationship exists between skin carotenoid levels and physical activity (PA) levels, although this has yet to be investigated in preschoolers. Purpose: As such, the purpose of this dissertation was to 1) evaluate the existing literature to identify the best approach, 2) design a study to assess the feasibility of an objectively-measured intervention informed by the best practices identified by the systematic review, and 3) explore the relationship between skin carotenoid scores (SCS) and PA in preschoolers. Methods: The best practices and existing gaps in this field was assessed using a systematic literature review (Manuscript I). This information was used to design a feasibility randomized-controlled trial within a local childcare center that assessed FV intake using the objective plate-waste method (Manuscript II). Additional factors included measurement of body mass index (BMI) percentile, socio-demographic factors, and at-home dietary intake. The relationship between skin carotenoids and PA was assessed objectively using skin carotenoid scores (SCS) and actigraphy (Actigraph GT3X) collected across three days (Manuscript III). Results: The results of the systematic review supported the use of an intervention informed by Social Cognitive Theory with components pertaining to nutrition education and repeated exposure to increase FV intake in preschoolers. As such, our study assessed such an intervention and established the feasibility of the proposed study design within a childcare setting using objective measures of dietary intake. Although this study was not adequately powered to assess changes in FV intake, it highlighted significant inter- and intra-subject variability in day-to-day FV intake in preschoolers, which should be further examined in future studies. Thirdly, SCS and PA were significantly associated in this sample of preschoolers (β = 3.448, p=0.032). Discussion: This study design and intervention informed by the existing literature was well-accepted by the participating childcare center personnel and included children and may be used to inform future interventions that aim to improve diet in preschoolers. Further, the association between SCS and PA supports the use of skin carotenoids as biomarker of health status, as opposed to solely FV intake. Conclusion: The findings of this dissertation contribute to the existing literature on health-related behaviors in preschoolers.
