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Citation:

McAleese JD, Rankin LL. Garden-based nutrition education affects fruit and vegetable consumption in sixth-grade adolescents. J Am Diet Assoc. 2007; 107(4): 662-665.


PubMed ID: 17383272
Study Design:
Non-Randomized Controlled Trial
Class:
C - Click here for explanation of classification scheme.
NEUTRAL: See Research Design and Implementation Criteria Checklist below.
Research Purpose:

To measure the effects of garden-based nutrition education on fruit and vegetable consumption in adolescents using a non-equivalent control group design.

Inclusion Criteria:

Participants had to be sixth grade students attending Public School District 25 in Bannock County, Pocatello, ID, with signed parental consents and child assent forms.

Exclusion Criteria:

Participants who did not complete at least two food-recall workbooks before and two food-recall workbooks after the intervention were dropped from the behavioral analysis.

Description of Study Protocol:

Recruitment

Subjects were recruited from sixth grade classes in three similar elementary schools in southeast Idaho. 

Design

  • Group non-randomized controlled trial
  • A control school and one experimental (experimental school 1) were assigned and a second experimental school (experimental school 2) was assigned based on garden availability\
  • Selected schools were convenience samples. 

Intervention

  • Participants completed three consecutive 24- hour food-recall workbooks before as well as after the 12-week intervention. The workbooks were validated by B. Jendrysik. Workbooks were administered in assigned classrooms by the six-grade teachers who received training before the study and received instructions to respond to student questions without guiding student answers. Before the first workbook administration, students received instructions from the principal investigator (PI) on how to report food intake accurately. Food-recall workbooks included age-appropriate instructions, portion size illustrations, and other explanations on completion of the workbook. After workbooks were completed, they were placed in an envelope and given to the PI at the end of the day. Food recalls were checked for completeness by the PI
  • Control school: Subjects (N=25) completed three food-recall workbooks before and three after the intervention. No further intervention was carried out at the control school 
  • Experimental school 1: In addition to the food-recall workbooks, the subjects (N=25) participated in a 12-week nutrition education program. The nutrition curriculum guide, Nutrition in the Garden, was developed by Lineberger and Zajicek. This curriculum provided lessons and activities that combined nutrition and horticulture
  • Experimental school 2: Subjects (N=45) completed the food-recall workbooks and participated in the 12-week nutrition education program. In addition, subjects participated in hands-on garden-based activities designed to correspond to the nutrition curriculum. The school garden was in walking distance of the school. Subjects participated in maintaining the garden over the 12 weeks through weeding, watering, and harvesting. They also participated in other activities, including a salsa-making workshop, class cookbook, "add a veggie to lunch" day, planting and harvesting, herb drying and food experiences with fruits and vegetables harvested from the garden. 

Statistical Analysis

  • A repeated measures one-way factorial analysis of variance (ANOVA) was conducted using the number of fruits and vegetable servings consumed and the daily intake of vitamin A, vitamin C and fiber before and immediately after the 12-week intervention. SPSS v 13.0 was used for analyses
  • A P-value of 0.05 was used to indicate statistical significance
  • Post-hoc analysis using a Bonferroni adjustment was used to determine where the interaction occurred.

 

Data Collection Summary:

Timing of Measurements

Food recall workbooks were completed at the beginning and at the end of a 12-week nutrition education curriculum. 

Dependent Variables

  • Fruit intake measured as daily serving(s)
  • Vegetable intake measured as daily serving(s)
  • Vitamin A intake (mcg retinol activity equivalents per day)
  • Vitamin C intake (mg per day)
  • Fiber intake (g per day).

Independent Variables

  • Control school
  • Experimental school 1
  • Experimental school 2. 

 

Description of Actual Data Sample:
  • Initial N: 122 participants
  • Attrition (final N): 99 participants (44% males)
  • Age: Mean age of 11.1 years with range of 10 to 13 years
  • Other relevant demographics: Authors noted that sample populations at each school contained a similar representation of ethnic, cultural and socioeconomic traits; however documentation of such was not provided
  • Location: Pocatello, ID.
Summary of Results:

Key Findings

  • No significant differences were seen in fruit servings, vegetable servings, vitamin A, Vitamin C or fiber intake based on gender or age
  • Fruit, vegetable, vitamin A, vitamin C and fiber intake increased significantly from baseline to 12 weeks for the participants in the experimental school 2 
  • Participants in the experimental school 2 (nutrition education and garden-based activities) increased their intake of fruit, vegetable, vitamin A, vitamin C and fiber intake more than those in the control group or experimental school 1.

Intakes of Fruits, Vegetables, Fiber, Vitamins A and C of Sixth-grade Adolescents at Three Schools in Southeast Idaho, Before and After Study Interventions Using ANOVA and Bonferroni Post-hoc Analysis (N=99)

  CS (N=25) ES1 (N=25) ES2 (N=45)  
  Before After Before After Before After F P-value
  Mean±SD Mean±SD Mean±SD Mean±SD Mean±SD Mean±SD    
Fruits (servings) 0.7±0.6 0.6±0.7 0.3±0.5 0.5±0.7 0.8±0.8 1.9±1.4 10.98 <0.001
Vegetables (servings) 1.7±0.7 1.4±0.7 1.8±1.1 1.7±1.0 1.2±0.6 2.6±1.7 15.00 <0.001
Vitamin A (μgRAE) 621.4±294.1 549.5±248.5 428.5±247.9 358.8±273.3 430.4±244.1 612.4±359.6 5.86 0.004
Vitamin C (mg) 83.1±115.6 76.2±8.0 47.5±48.5 60.8±126.6 58.2±62.2 143.4±144.5 4.31 0.016
Fiber (g) 15.3±6.0 12.6±8.0 10.7±5.0 9.9±5.0 12.7±4.6 16.9±7.4 8.21 0.001

CS: Control school

ES1: Experimental school 1

ES2: Experimental school 2

RAE: Retinol activity equivalents 

Other Findings

No significant findings occurred in fruit, vegetable, vitamin A, vitamin C or fiber intake at the control school or experimental school 1 (nutrition education only). 

Author Conclusion:

This study illustrates the efficacy of using garden-based nutrition education when attempting to increase adolescents' consumption of fruits and vegetables.

Reviewer Comments:
  • This study used a convenience sample of schools
  • Relatively small numbers of subjects in groups
  • 12 weeks is a short time period to assess behavior change
  • The use of self-reported data and additional influences on students' food intake, such as eating at home, parental influences and additional classroom activities, may have affected these results. 

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)
Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?
Yes
  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?
Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies)
Yes
 
Validity Questions
1. Was the research question clearly stated?
Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?
Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated?
Yes
  1.3. Were the target population and setting specified?
Yes
2. Was the selection of study subjects/patients free from bias?
No
  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?
Yes
  2.2. Were criteria applied equally to all study groups?
Yes
  2.3. Were health, demographics, and other characteristics of subjects described?
No
  2.4. Were the subjects/patients a representative sample of the relevant population?
No
3. Were study groups comparable?
Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)
Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?
Yes
  3.3. Were concurrent controls used? (Concurrent preferred over historical controls.)
Yes
  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?
N/A
  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.)
N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?
N/A
4. Was method of handling withdrawals described?
Yes
  4.1. Were follow-up methods described and the same for all groups?
Yes
  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%.)
No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for?
Yes
  4.4. Were reasons for withdrawals similar across groups?
Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study?
N/A
5. Was blinding used to prevent introduction of bias?
No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?
No
  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.)
No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?
N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status?
N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results?
N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?
Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied?
Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described?
N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?
Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured?
Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described?
N/A
  6.6. Were extra or unplanned treatments described?
N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?
N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient?
N/A
7. Were outcomes clearly defined and the measurements valid and reliable?
Yes
  7.1. Were primary and secondary endpoints described and relevant to the question?
Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern?
Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur?
Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?
Yes
  7.5. Was the measurement of effect at an appropriate level of precision?
Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes?
No
  7.7. Were the measurements conducted consistently across groups?
Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators?
Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately?
Yes
  8.2. Were correct statistical tests used and assumptions of test not violated?
Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals?
Yes
  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)?
N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?
Yes
  8.6. Was clinical significance as well as statistical significance reported?
Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error?
N/A
9. Are conclusions supported by results with biases and limitations taken into consideration?
Yes
  9.1. Is there a discussion of findings?
Yes
  9.2. Are biases and study limitations identified and discussed?
Yes
10. Is bias due to study’s funding or sponsorship unlikely?
Yes
  10.1. Were sources of funding and investigators’ affiliations described?
Yes
  10.2. Was the study free from apparent conflict of interest?
Yes
 
 

Copyright American Dietetic Association (ADA).