Vegetarian Nutrition

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Kim EHJ, Schroeder KM, Houser RF, Dwyer JT. Two small surveys, 25 years apart investigating motivations of dietary choice in two groups of vegetarians in the Boston area. J Am Diet Assoc. 1999; 99: 598-601.

 
Study Design:
Longitudinal (comparison of two cross-sectional studies)
Class:
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To investigate health, philosophical, ethical, religious attitudes and motivations, nutrition knowledge and eating practices of two groups of vegetarians residing in the area of Boston, Massachusetts in 1974 and 1997.

Inclusion Criteria:

Respondents who completely avoided all animal products (vegan) and those who avoided meat, fish, poultry, but consumed eggs and dairy (ovolactovegetarians) were included and classified as vegetarians.

Exclusion Criteria:

None reported.

Description of Study Protocol:

Recruitment

  • In 1974, the survey was distributed to customers of health food stores and traditional supermarkets
  • In 1997, the survey was distributed at a vegetarian food fair. 

Design

Longitudinal design comparing the outcomes of two cross-sectional studies.

Blinding Used

None reported.

Statistical Analysis

One-way ANOVA with least significance difference and non-parametric Kruskall-Wallis independent sample tests; Pearsons correlation coefficient. Significance set at α=0.05.

Data Collection Summary:

Timing of Measurements

One time in 1974 and another in 1997.

Dependent Variables

Attitudes and behaviors (measured or analyzed according to frequency answered).

Independent Variables

  • Vegetarians or non-vegetarians
  • Demographics (gender, education and age).

Control Variables

None reported.

Description of Actual Data Sample:

Initial N

  • In 1974: N=445 (184 males, 261 females; 36 vegetarians, 409 non-vegetarians)
  • In 1997: N=201 (73 males, 128 females; 116 vegetarian, 85 non-vegetarians.

Attrition (Final N)

None.

Age

  • Less than 20 years: 19 in 1974, 16 in 1997
  • 20 to 24 years: 157 in 1974, 40 in 1997
  • 25 to 29 years: 138 in 1974, 40 in 1997
  • 30 years or older: 131 in 1974, 105 in 1997.

Ethnicity

None reported

Other relevant demographics

  • Marital status
    • Single: 228 in 1974, 88 in 1997
    • Single (widowed, divorced or separated): 47 in 1974, 22 in 1997
    • Married: 114 in 1974, 74 in 1997
    • Living together: 56 in 1974, 17 in 1997.
  • Education level
    • High school: 60 in 1974, 15 in 1997
    • Technical, some college: 140 in 1974, 52 in 1997
    • College graduate, some graduate or professional school: 162 in 1974, 94 in 1997
    • Masters degree or doctorate or professional school: 83 in 1974, 40 in 1997.

Anthropometrics

None applicable.

Location

Boston, Massachusetts.

Summary of Results:
Variables Score Range 1974 1997 Statistical Significance
Vegetarian Non-vegetarian Vegetarian Non-vegetarian
Health Attitudes
9-27
23.4±3.8
22.2±4.6
21.8±4.9
23.1±3.9
NS
Philosophical Attitudes
8-24
19.2±3.2
16.1±4.0
20.7±2.2
18.0±3.6
P<0.05
Ethical Attitudes
4-12
8.9±1.7
7.1±2.1
10.0±1.9
8.3±2.5
P<0.05
Religious Attitudes
5-10
8.2±1.7
6.1±1.3
6.6±1.6
6.3±1.6
P<0.05
Nutrition Knowledge
0-7
4.6±0.8
4.1±1.2
4.8±1.3
4.8±1.1
NS
Supplement Use
4-16
6.8±2.7
8.3±3.8
8.5±3.4
9.6±4.1
P<0.05

Other Findings

  • Responses for vegetarians in 1997 were examined using Pearson correlation coefficients: A positive but weak correlation was found with health attitudes and philosophical (R=0.24, P<0.05), ethical (R=0.29, P<0.01) and religious attitudes (R±40, P<0.0001). This indicates that respondents who placed importance on health also cited philosophical, ethical and religious factors as having an influence on their dietary choices.
  • In the same 1997 group, philosophical attitudes were correlated with ethical (R=0.43, P<0.0001) and religious attitudes (R=0.22, P<0.05) and ethical attitudes were correlated with religious attitudes (R=0.29, P<0.01).

Factors more important to vegetarians in 1997 than in 1972:

  • Philosophical reasons
  • Ethical reasons.
Author Conclusion:

Dietary choices of vegetarians are the result of an integration of multiple attitudes and beliefs.

Funding Source:
Government: USDA #53/3-K06-5-10
Industry:
Reviewer Comments:
  • Good study that did address the research question: What are the motivations behind vegetarians? It did not focus on adolescents: Only a small percentage of the participants were less than 20 years old.
  • Did not address the question of how dietary pattern or nutrient intake is affected
  • Limitations were not addressed and for the vegetarian groups, the numbers were highly skewed. In 1997 the number of participants were significantly larger than the numbers of vegetarians participating in 1974.
  • Similarly, the sampling methods were different for the two years under review
  • The response rate for both years were not very strong (48% in 1974 and 62% in 1997).
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) N/A
  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) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? 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
  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) N/A
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? 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) N/A
  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
  3.2. 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
  3.3. 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? No
  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? No
  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
  3.5. 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
  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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  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. 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
  5.1. 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
  5.2. 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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
  6.2. 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? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? 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
  6.6. 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
  6.7. 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
  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. 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
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? 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
  7.4. 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? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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
  8.6. 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
  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? No
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
  9.2. Are biases and study limitations identified and discussed? No
  10. Is bias due to study's funding or sponsorship unlikely? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes