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HD: Food Security (2011)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

The purpose of the study was to determine if lower-cost diets among low-income women in California were energy-dense, but nutrient-poor.

Inclusion Criteria:
  • Non-institutionalized low-income women between the ages of 20 and 55 years living in four counties in California (urban, suburban and rural areas).
  • Additional criteria included:
    • Meeting low-income specifications (i.e., 185% poverty, $37,000 for a family of four in 2006)
    • Reading and speaking English
    • Serving as the major food purchaser-preparer for the family
    • Accessible by phone.
Exclusion Criteria:

Exclusion criteria included:

  • Non-English speakers
  • Middle and upper income
  • Pregnant and lactating women
  • Men
  • Women living in shelters and rehabilitation centers (since this group's allotment of food stamps is typically turned over to the institution to cover the costs of their food).
Description of Study Protocol:

Recruitment

Traditional recruitment sites for the Expanded Food and Nutrition Education Program (EFNEP) and Food Stamp Education (FSNE) served as recruitment sites. Sites included the following:

  • Community centers in low-income areas
  • Health clinics
  • Food Stamp Program offices
  • The Supplemental Program for Women, Infants and Children (WIC)
  • Social service agencies serving low-income groups.

Flyers were posted at sites and participants were invited to participate, giving them the option to begin the first round of data collection immediately or by making an appointment.

Design

This cross-sectional study used five meetings per person to deliver the dietary intake assessment to determine diet energy density and nutrient density of the participant's diet.

Statistical Analysis

  • Bivariate methods were used to explore the relationship between dietary energy density and energy-adjusted diet costs, which are both continuos variables. These variables were later stratified into tertiles to explore crude differences in mean intakes of key nutrients.
  • Significance of difference was tested with one-factor analyses of variance and correlation analysis was used to test the relation of dietary energy density and diet costs.
Data Collection Summary:

Timing of Measurements

  • Five interviews were collected over a period of time with the participants
  • Participants completed a food-frequency questionnaire with the reference point being within the past three months.
Description of Actual Data Sample:
  • Initial N: This number was not provided
  • Attrition (final N): 112 women
  • Age: Mean, 35.5±9.7 years (age ranged from 18 to 45 years)

Ethnicity

  • Non-Hispanic white: 37.5%
  • Hispanic: 33.9%
  • Non-Hispanic black: 9.8%
  • Asian/Pacific Islander: 9.8%
  • American Indian: 8.9%.

Other Relevant Demographics

  • Average household size: 4.2±2.0
  • 80% reported monthly incomes of not more than $1,500
  • 89.2% completed high school or greater.

Location

Four counties in California:

  • San Joaquin (urban, suburban and farm)
  • Solano (urban, suburban near coast)
  • Calavaras (rural)
  • Tulare (urban, farm, in valley).
Summary of Results:

Key Findings

Mean energy and nutrient intake and diet by tertile of dietary energy density for all food items for low-income women.

 

Lowest Tertile (N=39)

Middle Tertile (N=37)

Highest Tertile (N=36)

 P2

Dietary Energy Density (kcal/g)

1.20±0.12

1.53±0.08

1.90±0.22
<0.001 

Energy (kcal)

1598±620

1675±623

1824±775
0.35 

Total Fat (g)

67.5±30.3

77.1±30.5

94.8±41.0
0.003 
Total SFA (g)
20.1±9.5
23.3±9.5
29.4±12.7
<0.001
Total Dietary Fiber (g)
20.5±8.2
17.3±6.3
14.8±7.1
0.004
Added Sugars (g)
37.8±18.2
41.4±25.5
47.3±32.8
0.29
Vitamin A (IU)
12,309±7027
7783±4164
5497±3533
<0.001
Vitamin C (mg)
108±55
67±25
54±32
<0.001
Calcium (mg)
658±285
613±253
583±282
0.49
Iron (mg)
13±5
13±5
12±6
0.72
Potassium (mg)
2443±943
2039±721
1901±817
0.017
Dietary Energy Cost ($/2,000 kcal)
6.86±0.82
5.99±0.70
5.54±0.61
<0.001

 

Other Findings

  • With all beverages excluded, mean daily energy intake was 7.1MJ and mean dietary energy density was 6.5MJ per kg
  • Stratifying samples in tertiles revealed that higher dietary energy density is associated with significantly higher intakes of total fat (P=0.003) and saturated fat (P<0.001) and with significantly lower intakes of dietary fiber (P=0.004), vitamin A (P<0.001) and vitamin C (P<0.001)
  • With caloric and non-caloric beverages (drinking water excluded), mean daily energy intake was 8.6MJ and mean dietary energy density was 3.9MJ per kg. Caloric beverages contributed to a mean of 362kcal per day to a woman's diet.
  • With beverages excluded, the daily diet cost of food was $5.12 and the energy-adjusted diet-cost was $6.08 per 8.4MJ
  • Lower diet cost was associated with significantly higher dietary energy density (P<0.001), total fat (P=0.024) and saturated fat (P=0.025) and with significantly lower intakes of vitamin A (P=0.003) and C (P<0.001).

 

 

Author Conclusion:
  • Dietary energy density was inversely associated with dietary quality, as determined by macro- and micronutrient intakes, which is consistent with observations outside of the United States
  • Authors also noted that low-income women eating less-energy dense diet (i.e., better diet quality) spent more money per calorie
  • More energy dense diets were associated with higher intakes of total and saturated fats
  • Dietary energy density was strongly and negatively linked to energy-adjusted diet costs
  • These findings have implications for low-income families in the United States and for the USDA's food assistance and education programs
  • Strategies for improving the quality of diet without increasing costs should be developed and included as part of the curriculum of the USDA.
Funding Source:
Government: USDA Cooperative State Research Education and Extension Service
University/Hospital: Nutrition Department and Western Human Nutrition Research, University of California and University of Washington
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? Yes
  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? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
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) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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? Yes
  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? ???
  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? ???
  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? N/A
  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.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  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? N/A
  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? 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? ???
  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)? 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