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Parmer SM, Salisbury-Glennon J, Shannon D, Struempler B. School gardens: an experiential learning approach for a nutrition education program to increase fruit and vegetable knowledge, preference, and consumption among second-grade students. J Nutr Educ Behav. 2009 May-Jun; 41 (3): 212-217.

PubMed ID: 19411056
Study Design:
Non-Randomized Controlled Trial
C - Click here for explanation of classification scheme.
NEUTRAL: See Research Design and Implementation Criteria Checklist below.
Research Purpose:

To examine the effects of a school garden on second grade students' fruit and vegetable knowledge, preference and consumption.

Inclusion Criteria:
  • Second grade students: Males and females
  • Living in the southeastern United States.
Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:


  • Investigators selected one elementary school in the southeastern United States with six second grade classes
  • School principal granted permission for investigators to work with teachers and students
  • Parental consent obtained for all participants.


  • Non-randomized controlled trial
  • Treatment assignments based on individual classroom teacher's stated interests. This was a necessary condition of the study. 


Three treatment groups: Nutrition Education and Gardening Group (NE+G); Nutrition Education Only Group (NE); Control Group (CG).

  • The NE+G treatment group also participated in hands-on gardening experiences: Children planted seeds and plants (carrots, broccoli, spinach and cabbage) and maintained a school garden (watering, weeding, pest management) with adult supervision. Children also prepared Party Confetti Salad using produce obtained from the garden.
  • Two second-grade classes were assigned to each treatment group
  • Curriculum used in the study: Pyramid Cafe and Health and Nutrition from the Garden
  • The study, including pre- and post-assessments lasted 28 weeks. The NE+G group received one hour of nutrition education lessons every other week and one hour of gardening lessons every alternating week. The NE group received one hour of nutrition education lessons every other week. The CG only participated in pre- and post-assessments.
  • Evaluation tools: Fruit and vegetable survey, fruit and vegetable preference questionnaire, and lunchroom observation. Pre and post evaluations were conducted by the primary investigator immediately prior to and following the intervention. Evaluation tools were developed using previously-validated measures.
  • Fruit and vegetable survey: Measures fruit and vegetable knowledge and preferences; 16 items measured FV knowledge (MyPyramid food groups, nutrient-food relationships and nutrient-job associations) using two question formats. The preference section consisted of 15 food items rated on a three-point scale.
  • Fruit and vegetable preference questionnaire: Taste and rate methodology developed by Birch and Sullivan; participants tasted five vegetables (carrots, broccoli, spinach, zucchini and cabbage) and one fruit (blueberry) and then rated their taste enjoyment on a five-point scale. Assessments were completed independently away from other children. Fruits and vegetables were presented raw and plain, cut-up and served in two-ounce portions. 
  • Lunchroom observation: Children could select one of two meal choices (school plate lunch or grab-and-go lunch). The primary investigator observed participants for two lunch meals each at pre- and post-assessment and recorded the type of lunch selected, vegetable items selected by child and the amount of vegetables consumed by child.

Statistical Analysis

  • SPSS used to analyze data
  • Descriptive statistics to describe the study sample
  • Mixed-model analysis of variance (ANOVA) to compare the mean scores among the three groups at pre and post
  • Level of statistical significance: A=0.05.
Data Collection Summary:

Timing of Measurements

Pre- and post-intervention.

Dependent Variables

  • Fruit and vegetable knowledge: Measured with the fruit and vegetable survey
  • Fruit and vegetable preference: Measured with the fruit and vegetable survey and the fruit and vegetable preference questionnaire
  • Fruit and vegetable consumption: Measured by lunchroom observation.

Independent Variables

Assignment to Nutrition Education and Gardening (NE+G) treatment group, Nutrition Education Only (NE) treatment group or Control Group (CG).

Control Variables


Description of Actual Data Sample:

Initial N

115 second-grade students (76 treatment, 39 control; 80 males, 35 females).

Attrition (Final N)

No attrition: Final N same as initial N.


  • NE+G Group: N=39; mean age, 7.3 years; 46% female
  • NE Group: N=37; mean age, 7.5 years; 27% female
  • CG: N=39; mean age, 7.4 years; 28% female.


Predominantly white.


Not provided.


Southeastern United States.

Summary of Results:

Key Findings

Fruit and Vegetable Knowledge

  • Results of the mixed-model ANOVA indicated an overall change in food group knowledge [F(1,112)=16.11, P< 0.001]. However, no interaction effect with group was found.
  • For nutrient-food association, there was a significant main effect for treatment [F(1,112)=54.48, P<0.001], as well as a significant interaction [F(2,212)=11.84, P<0.001]
  • Both treatment groups experienced significantly greater improvement gains (NE+G, T=6.6 and P<0.001; NE, T=5.3 and P<0.001) than the Control Group (T=0.3 and P=0.733)
  • For nutrient-job association, there was a significant main effect for treatment [F(1,112)=28.69, P<0.001], as well as a significant interaction [F(2,112)=12.05, P<0.001]. Paired T-test results indicated that both treatment groups had significantly greater improvement gains (NE+G, T=5.2 and P<0.001; NE, T=4.3 and P<0.001) in nutrient-job association knowledge over time than did the CG (T=0.9, P=0.351). For fruit and vegetable identification, there was a significant main effect for treatment [F(1,78)=58.73, P<0.001], as well as a significant interaction [F(2,78)=28.08, P<0.001].

Fruit and Vegetable Preference

  • Willingness to try fruits and vegetables, as measured by the fruit and vegetable preference questionnaire: An overall difference was found between the three groups [F(1,78)=5.617, P =0.005], with the treatment groups indicating a greater willingness to try fruits and vegetables than the Control Group. There was also an effect over time [F(1,78)=8.851, P=0.004], with all three groups becoming more willing to try fruits and vegetables over the duration of the study.
  • Ratings of tasted fruit and vegetables: There was a significant main effect for treatment [F(1,75)=17.63, P<0.001], as well as a significant interaction [F(2,75)=14.45, P<0.001). Paired T-tests indicated that both treatment groups rated fruits and vegetables significantly better tasting (NE+G, T=5.3 and P<0.001; NE, T=2.7 and P<0.001) at post-test, as compared to pre-test, than did the Control Group (T=1.2, P=0.227).

Fruit and Vegetable Consumption

  • Paired T-tests indicated that the NE+G Group was more willing to choose vegetables in the school lunch (T=3.19, P<0.01) at post-test, compared to pre-test, than was the NE Group (T=1.83, P=0.082) or the Control Group (T=0.73, P=0.466)
  • Consumption scores indicated two changes: First, the Control Group ate significantly fewer vegetables (T=-2.64, P<0.001) at post-test, as compared to the pre-test; second, the NE+G Group ate significantly more vegetables (T=3.04, P<0.01) at post-test, as compared to pre-test. The NE Group had no significant change in consumption.

Fruit and Vegetable Knowledge, Preference and Consumption of Second-Grade Students Before and After Participation in a Nutrition Education and Gardening Intervention



Group One: Nutrition Education+Gardening

Group Two: Nutrition Education Only

Group Three: Control Group

Mean Scores: Pre (SD)

Mean Scores: Post (SD)

Mean Scores: Pre (SD)

Mean Scores: Post (SD)

Mean Scores: Pre (SD)

Mean Scores: Post (SD)

Nutrition Knowledge

MyPyramid food groups

3.69 (1.8)

5.20 (1.2)

4.08 (1.7)

4.75 (1.9)

4.03 (1.8)

4.46 (1.3)

Nutrient-food association

1.46 (1.1)

3.56 (1.6)**

1.67 (1.5)

3.70 (1.8)**

1.82 (1.4)

1.92 (1.3)
Nutrient-job association
1.25 (1.0)
2.97 (1.9)**
1.27 (1.3)
2.64 (1.6)**
1.71 (1.2)
1.46 (1.0)
F and V identification
3.14 (0.7)
4.89 (0.9)**
3.03 (0.6)
3.44 (0.8)*
2.88 (0.9)
2.96 (1.0)
Fruit and Vegetable Preference
Willingness to taste
4.82 (1.6)
5.50 (1.0)
5.11 (1.1)
5.33 (1.2)
3.84 (2.1)
4.23 (2.0)
Ratings of tasted F and V's
3.45 (0.9)
4.38 (0.5)**
3.85 (0.8)
4.15 (0.6)**
3.99 (0.7)
3.82 (0.5)
Fruit preference
2.59 (0.4)
2.60 (0.3)
2.70 (0.3)
2.73 (0.3)
2.59 (0.4)
2.57 (0.3)
Vegetable preference
2.08 (0.5)
2.03 (0.5)
2.20 (0.6)
2.14 (0.6)
2.10 (0.5)
1.98 (0.5)
Vegetable Choice and Consumption
Vegetable choice
0.41 (0.3)
0.62 (0.2)*
0.36 (0.4)
0.48 (0.2)
0.42 (0.4)
0.40 (0.2)
Vegetable consumption
0.70 (0.4)
1.0 (0.0)*
0.64 (0.5)
0.64 (0.5)
0.83 (0.3)
0.50 (0.5)**

F indicates fruit
V indicates vegetable
SD indicates standard deviation.

Author Conclusion:
  • School-based gardening as a component of nutrition education is effective in increasing the fruit and vegetable knowledge, preference and consumption in children within elementary school settings
  • School gardens can positively influence the dietary habits of young children.
Reviewer Comments:

Authors note the following limitations:  

  • Gender composition of the second-grade classrooms (predominantly male)
  • Challenges conducting a study within a school-setting influenced the research design
  • Relatively small sample size
  • Study involves predominantly white second-grade population and results may not generalize to other populations.

Research Design and Implementation Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to nutrition or dietetics practice?
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies)
Validity Questions
1. Was the research question clearly stated?
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated?
  1.3. Were the target population and setting specified?
2. Was the selection of study subjects/patients free from bias?
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?
  2.2. Were criteria applied equally to all study groups?
  2.3. Were health, demographics, and other characteristics of subjects described?
  2.4. Were the subjects/patients a representative sample of the relevant population?
3. Were study groups comparable?
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?
  3.3. Were concurrent controls used? (Concurrent preferred over historical controls.)
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?
  3.5. If case control or cross-sectional study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable. Criterion may not be applicable in some cross-sectional studies.)
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?
4. Was method of handling withdrawals described?
  4.1. Were follow-up methods described and the same for all groups?
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for?
  4.4. Were reasons for withdrawals similar across groups?
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study?
5. Was blinding used to prevent introduction of bias?
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status?
  5.5. In diagnostic study, were test results blinded to patient history and other test results?
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were intervening factors described?
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied?
  6.2. In observational study, were interventions, study settings, and clinicians/provider described?
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured?
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described?
  6.6. Were extra or unplanned treatments described?
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?
  6.8. In diagnostic study, were details of test administration and replication sufficient?
7. Were outcomes clearly defined and the measurements valid and reliable?
  7.1. Were primary and secondary endpoints described and relevant to the question?
  7.2. Were nutrition measures appropriate to question and outcomes of concern?
  7.3. Was the period of follow-up long enough for important outcome(s) to occur?
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?
  7.5. Was the measurement of effect at an appropriate level of precision?
  7.6. Were other factors accounted for (measured) that could affect outcomes?
  7.7. Were the measurements conducted consistently across groups?
8. Was the statistical analysis appropriate for the study design and type of outcome indicators?
  8.1. Were statistical analyses adequately described and the results reported appropriately?
  8.2. Were correct statistical tests used and assumptions of test not violated?
  8.3. Were statistics reported with levels of significance and/or confidence intervals?
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?
  8.6. Was clinical significance as well as statistical significance reported?
  8.7. If negative findings, was a power calculation reported to address type 2 error?
9. Are conclusions supported by results with biases and limitations taken into consideration?
  9.1. Is there a discussion of findings?
  9.2. Are biases and study limitations identified and discussed?
10. Is bias due to study’s funding or sponsorship unlikely?
  10.1. Were sources of funding and investigators’ affiliations described?
  10.2. Was the study free from apparent conflict of interest?

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