Portion size can be used strategically to increase intake of vegetables and fruits in young children over multiple days: a cluster-randomized crossover trial

Abstract

ABSTRACT Background Although dietary guidelines recommend that vegetables and fruits make up half the diet, it is unclear whether serving vegetables and fruits in larger portions will have sustained effects on children's intake over multiple days. Objectives This study tested the effects on children's intake of 2 strategies for increasing the proportion of vegetables and fruits: either adding or substituting extra portions as side dishes at meals and snacks over 5 d. Methods In a cluster-randomized crossover design with 3 periods, we provided all meals and snacks for 5 d to 53 children aged 3–5 y in classrooms in their childcare centers. In the Control condition, we served typical portions for all food groups. In the Addition condition we increased portions of low-energy-dense vegetables and fruits by 50%, and in the Substitution condition we increased portions of vegetables and fruits by 50% and also reduced portions of other foods by an equivalent weight. Results For vegetables, the Addition strategy increased daily intake compared with Control by 24% (mean ± SEM = 12 ± 3 g/d; P = 0.0002), and the Substitution strategy increased intake compared with Control by 41% (22 ± 3 g/d; P < 0.0001). For fruits, consumption increased by similar amounts: Addition by 33% (60 ± 6 g/d) and Substitution by 38% (69 ± 8 g/d; both P < 0.0001). Both strategies increased vegetable and fruit intakes compared with Control across all 5 days (all P < 0.004), although the increase in fruit consumption with Addition declined over time (P < 0.0001). Daily energy intake compared with Control increased by 5% with Addition (57 ± 17 kcal; P = 0.001) but decreased by 6% with Substitution (−64 ± 21 kcal; P = 0.004). Conclusions Both the Addition and Substitution strategies promoted increases in vegetable and fruit intake over 5 d in preschool children. When excess energy intake is a concern, substituting vegetables and fruits for other foods is a better option than simply serving more. This trial was registered at http://www.clinicaltrials.gov as NCT03242863 (https://clinicaltrials.gov/ct2/show/NCT03242863), where the protocol is available.