EAL

HD: Food Security (2011)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine if an additional economic subsidy for fresh fruits and vegetables for postpartum WIC participants would result in increased consumption of fruits and vegetables.

Inclusion Criteria:

Women who recently had a baby and were recertified for WIC participation as either a breastfeeding or non-breastfeeding postpartum women
Spoke English or Spanish
Were 18 years or older
Resided in Los Angeles, California.

Exclusion Criteria:

Younger than 18 years old.

Description of Study Protocol:

Recruitment

Women enrolling for WIC services in Los Angeles, California at three study sites
From February to August 2001
Sites selected based on similarity of:
- Caseload
- Ethnic backgrounds
- Proximity of supermarkets and farmers' markets to ensure equal access to fresh fruits and vegetables [a major supermarket and year-round farmers market must be within walking distance (less than 1/2 mile) from where participants shopped at each of three study sites].

Design

Non-randomized control trial.

Intervention

Supermarket group was issued $10 worth or vouchers per week in $1.00 units to buy produce of the participants' choice

Farmers' market group was issued $10 worth of vouchers per week in $2.00 units to buy produce of the participants' choice
Vouchers were issued bimonthly and could be spent over the two-month period
Two-month monitoring period to document baseline fruit and vegetable intake
Six-month period of intervention and six months of follow-up.

Control Group

Issued a set of coupons valued at $13 per month redeemable for disposable diapers to compensate for interview time.

Statistical Analysis

Bi-variates analyses done using analysis of variance, person-product moment correlation and paired T-test
Linear regression conducted to identify predictors of fruit and vegetable intake six months after intervention
Mixed models used to detect change in fruit and vegetable intake at the end of intervention and at six-month follow-up:
- Allows for intra-subject correlation
- Adjusts for covariates.

Data Collection Summary:

Timing of Measurements

Baseline (two-month monitoring period)
End of six-month intervention
Six months following end of intervention.

Dependent Variables

Fruit and vegetable intake.

Independent Variables

Vouchers for supermarket site
Vouchers for farmers' market site.

Other Variables

Household demographic variables
Program participation (Medi-Cal, Food Stamp Program, Temporary Assistance for Needy Families)
Pregnancy outcomes
Infant feeding practices
Height, weight and BMR
Food security status, assessed by the US Food Security Survey Module.

Control Variables

Women
Energy intake
Recently having a child.

Description of Actual Data Sample:

Initial N: 602 women
Attrition (final N): 451 women (75%)
Age:
- Mean age: 27.5±5.8 years
- Range: 17 to 43 years
Ethnicity:
- 89.1% Hispanic
- 5.9% African American
- 2.8% non-Hispanic white
- 1.9% Asian American
- 0.2% American Indian
Other relevant demographics:
- Mean educational level: 9.3±3.2 years (range zero to 16 years)
- Mean family size: 4±1.3 persons (range two to 11)
- Mean household income: $1,233±$617 per month (range $0 to $3,120 per month)
- Resided in US approximately 12.5±9.5 years
- Participated in WIC approximately 2.8 years
- Mean BMI: 28.1kg/m²
- Mean estimated energy intake: basal metabolic rate (EI:BMR) ratio was 1.6±0.64
- Approximately one third of subjects exclusively breastfed their infants at study entry
- Differences between groups:
  - Participants at farmers' market site had higher rates of exclusive breastfeeding than did participants at supermarket site or control site
  - Participants at farmers' market site had higher rates of Medi-Cal participation and food security as compared to supermarket site or control site
  - Average energy intake was lower for the control site than for either intervention sites
Location: Los Angeles, California.

Summary of Results:

Key Findings

Total consumption of fruits and vegetables increased over the course of the study.

	Fruit and Vegetable Intake (Servings per 1,000kcal) Baseline	Fruit and Vegetable Intake (Servings per 1,000kcal) End of Intervention	Fruit and Vegetable Intake (Servings per 1,000kcal) Six-month Follow-up
Farmers' Market	2.2	3.9 (P<0.001)*	4.0 (P=0.001)*
Supermarket	2.9	4.1 (P<0.001)*	4.0 (P=0.001)*
Control	2.6	3.0	3.1

* Statistically significant difference when compared to control group at same time period controlling for energy intake.

Other Findings:

Fruit intake only: Total fruit intake did not significantly increase over time for the intervention sites compared to control site
Vegetable intake only:
- Total vegetable intake was higher at both intervention sites compared to the control site at the end of the intervention period; this significance remained after controlling for multiple comparisons and excluding beans and potatoes
  - Farmers' market: 2.1 servings per 1,000kcal, P<0.001
  - Supermarket: 2.3 servings per 1,000kcal, P<0.001
  - Control: 1.5 servings per 1,000kcal
- Total vegetable intake at six months after intervention remained higher at both sites compared to control when adjusting for multiple comparisons and excluding beans and potatoes
  - Control vs. farmers' market, P=0.007
  - Control vs. supermarket P=0.023
Higher reported intake of fruits and vegetables six months after the intervention was associated with:
- Higher reported fruit and vegetable intake at baseline
- Preference for speaking Spanish
- Either the supermarket site or farmers' market site.
Mixed modeling: Comparing data over time
- Total fruit and vegetable consumption:
  - Significantly increased at the end of intervention compared to the control group from baseline for both the farmers' market and supermarket sites
    - Farmers' market: Increased consumption by 1.4 servings per 1,000kcal (P<0.001)
    - Supermarket: Increased consumption by 0.8 servings per 1,000kcal (P<0.02)
  - There was also a significant increased compared with the control group of 1.15 servings per 1,000kcal from baseline to six months after intervention (P<0.001)
- Fruit intake only:
  - Significant increase of 0.51 servings per 1,000kcal from baseline to end of intervention for farmers' market group compared with control
  - Increase remained significant at six months after intervention
  - Recent immigrants tended to consume more fruits than those who had been in the United States longer (P=0.05).
- Vegetable intake only:
  - Intake increased 0.89 servings per 1,000kcals (P<0.001) for farmers' market site and 0.57 servings per 1,000kcals (P=0.02) for those at the supermarket site compared to control from baseline to end of intervention
  - Intake increased 0.65 servings per 1,000kcals (P<0.01) for farmers' market site from baseline to six months after the intervention compared to controls
  - Increased vegetable intake was significantly associated with being older (P=0.05), participants who bottlefed their infants six months after the intervention (P<0.01) and were either African American or white (P=0.05).

Author Conclusion:

The intervention increased fruit and vegetable intake in both of the treatment groups (farmers' market and supermarket sites) and the increase was sustained six months after the end of the intervention
Increase was primarily due to increases in consumption of vegetables
Results support the recommendations of the Institute of Medicine to add fresh fruits and vegetables to the WIC food packages to result in the desired outcome of increasing fruit and vegetable consumption in this population of women.

Funding Source:

Government:	California Cancer Research Program, California Department of Health Services; National Institutes of Health through University of California, Los Angeles
University/Hospital:	University of California at Davis
In-Kind support reported by Industry:	Yes

Reviewer Comments:

Quality 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 dieteticspractice?	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?	No
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	No
3.	Were study groups comparable?		No
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	No
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	No
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	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 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.)	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?		No
	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	No
	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?	???
	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?	No
	6.6.	Were extra or unplanned treatments described?	No
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	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?	Yes
	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)?	Yes
	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?	No
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