BACKGROUND

In the development of early child food preferences, it is important to understand the basic relationship between repeated exposure to a food (or foods) and acceptability of an exposed food, as well as how repeated exposure to a food (or foods) generalizes to acceptability of a different food either within the same food category (e.g. fruit or vegetable) or in a different food category as the exposed food. Systematic reviews were conducted as part of the U.S. Department of Agriculture and Department of Health and Human Services Pregnancy and Birth to 24 Months Project. The goal of this systematic review was to examine the following question: What is the relationship between repeated exposure (timing, quantity, and frequency) to foods and early food acceptance?

CONCLUSION STATEMENT AND GRADES

Moderate evidence from randomized controlled trials indicates that tasting a single or multiple vegetable(s) or fruit(s) 1 food per day for 8 – 10 or more days is likely to increase acceptability of an exposed food (indicated by an increase in food intake or faster rate of feeding after compared to before the exposure period) in infants and toddlers 4 to 24 months old. The effect of repeated exposure on acceptability is likely to generalize to other foods within the same food category but not to foods from a different food category. This evidence does not address the effect of repeated exposure of foods beyond vegetables and fruits on food acceptability in infants and toddlers. : Moderate.

METHODS

This systematic review was conducted by a team of staff from the Nutrition Evidence Systematic Review team in collaboration with a Technical Expert Collaborative. Literature search was conducted using 12 databases to identify articles that evaluated the intervention or exposure of repeated exposure to a food(s) and the outcomes of food acceptability. A manual search was conducted to identify articles that may not have been included in the electronic databases searched. Articles were screened by two authors independently for inclusion based on pre-determined criteria. Data extraction and risk of bias assessment were conducted for each included study, and both were checked for accuracy. The body of evidence was qualitatively synthesized to inform development of a conclusion statement(s), and the strength of evidence was graded using pre-established criteria evaluating the body of evidence on internal validity/risk of bias, adequacy, consistency, impact, and generalizability.

SUMMARY OF EVIDENCE

Twenty-one articles (14 RCTs, 5 non-randomized controlled trials, and 2 cohort studies) met criteria for inclusion that examined repeated exposure to a food(s) and food acceptability: 5 of 21 articles had considerable issues with directness and generalizability and did not contribute to the evidence synthesis. Repeated exposure to a single vegetable or fruit or multiple vegetables or fruits resulted in increased acceptance of an exposed food after 8 – 10 or more exposures. The goal of most of the studies was not to determine the minimum number of exposures that were necessary to see an effect on acceptability. Therefore, fewer than 8 exposures may be sufficient for some infants and toddlers to increase acceptability of an exposed food and there may be times when a child may never like a particular food regardless of the number of exposures. The effect of repeated exposure can generalize to similar foods. That is, repeated exposure of a food(s) may increase acceptability of similar foods but this generalization is less likely to occur with foods that are not similar, like foods from a different food category. In many cases, when infants demonstrated increased acceptability of a food, either by increased food intake or rate of feeding after compared to before repeated exposure, mothers were often unaware of the change in acceptability. Findings are limited to the effects of repeated exposure mostly to mostly vegetables with fewer studies looking at the effects of repeated exposure to fruits. Most test foods were commercially-available purees, and studies did not focus on a transition to table foods.