EAL

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To identify attitudes, health behavior, social adjustment and self-reported health of vegetarian teenagers and determine characteristics independently related to being vegetarian.

Inclusion Criteria:

Grade nine students from seven secondary schools (five public and two Catholic) invited to participate in the Hamilton-Wentworth and Niagara regions of Ontario, Canada during the year of 1999.

Exclusion Criteria:

Private secondary schools

Description of Study Protocol:

Recruitment

Seven schools were approached, all agreed to participate and all grade nine students were invited to participate
Community program consultants introduced the study to the school administrative staff, teachers and students
Parents received information letters and indicated their agreement or refusal to have their child participate.

Design

This was a cross-sectional observational study using a questionnaire
Questionnaire took 40 to 60 minutes to complete
Questionnaire used responses to questions in the following areas: School behavior and performance, risk taking behaviors, tobacco, alcohol, and drug use, weight and height, dieting behavior, vegetarian eating, self-reported health, and importance of selected issues.

Blinding Used

A face sheet was attached to each questionnaire with the students name and unique ID code (also appearing on the questionnaire). Face sheets were detached from questionnaires before collection.

Statistical Analysis

Frequency Analyses
Univariate logistic regression P<0.05
Logistic regression
- Variables with univariable association at P<0.25 were considered for entry
- Variables were selected at P<0.10
- Variables form the literature that were expected to strongly influence the choice to be vegetarian were forced into the model if they were not statistically significant.

Data Collection Summary:

Timing of Measurements

During the subjects' ninth grade school year in 1999

Dependent Variables

Diet type
- Vegetarians: Defined in this study to include vegan, lacto-ovo, lacto, ovo and semi-vegetarian
  - Vegan: Those who consume only fruits, vegetables, legumes, nuts, seeds and grains
  - Lacto-ovo: Those who consume dairy and egg products and avoid other animal products
  - Lacto: Those who consume milk products, but otherwise a plant based diet
  - Ovo: Those who consume egg products, but otherwise a plant based diet
  - Semi-vegetarian: Include eggs and dairy products, some fish and/or poultry but avoid red meat
- Omnivores: Defined in this study as those consuming red meat at least monthly.

Independent Variables

Based on responses to from the Opening Doors Student Self-Report Questionnaire in the following areas:

School behavior and performance (10 questions)
Risk taking behaviors (eight questions)
Tobacco alcohol and drug use (five questions)
Weight and height (two questions)
Dieting behavior (two questions)
Vegetarian eating (two questions)
Self-reported health (one question)
Importance of selected issues (five questions).

Dietary status was assessed using 19 items based on the Health Behaviors of School Aged Children Study and the School Health Project Questionnaire; this focused on self-reported consumption of the following:

Red meats (two questions)
Poultry (one question)
Fish (one question)
Eggs (one question)
Milk products (three questions)
Protein or milk alternatives (four questions).

Description of Actual Data Sample:

Initial N

1,574 students invited; 642 agreed to participate

Attrition (final N)

605 (37 were questionnaires discarded due to unreliable or incomplete responses)
Vegetarian final N was 25.

Age

13.9+ 0.37

Ethnicity

Unknown

Other relevant demographics

52.7% (315) female
48% (290) male
4% (25) of the population was classified as vegetarian; 22 female, three male.

Anthropometrics

Self-reported, BMI calculated (from self-reported heights and weights), proportions of omnivores and vegetarians who were overweight or obese were similar.

Location

Hamilton-Wentworth and Niagara regions of Ontario, Canada

Summary of Results:

4% of the study population was classified as vegetarian
- 2.5% lacto- or ovo-vegetarians
- 1.4% semi-vegetarians
- 0% vegans
88% (22 out of 25) of the vegetarians were female.

Factors associated with dietary status (univariable relationships (P,0.05))

Vegetarians are more likely to:
- Be female
- Report attitudes that animals are important
- Find losing weight important
- Currently be on a diet
- Have dieted in the past year
- Smoked in the past four weeks
- Consumed alcohol in the past four weeks
- Reported worsening health
- More risk behaviors
- Poorer school behaviors
Omnivores are more likely to state health is important.

Because 22 of 25 subjects classified as vegetarian were female the multivariate analysis was limited to females.

Dieting more than 10 times per year was much more common among female vegetarians compared to female omnivores.

Factors associated with vegetarian dietary status in female adolescents (multivariable analysis)

Variables	Odds Ratio	95% Confidence Interval
Dieting to lose weight in the past	9.88	(2.19-44.47)
Alcohol consumption, past four weeks	2.91	(1.02-8.32)
My health is very important**	0.38	(0.14-1.05)
Animal rights are very important**	2.65	(0.89-9.51)
Percentage concordant	79.9%
Hosmer & Lemeshow goodness-of-fit test (P-value)	0.817

In short,

Vegetarian females were almost ten times more likely to diet to lose weight in the last year than omnivore females
Vegetarian females were also almost three times more likely to consume alcohol in the past four weeks than omnivore females
The final model correctly classified about 80% of the subjects.

**Did not reach statistical significance

Author Conclusion:

Alcohol use was independently associated with teenage vegetarian eating
Weight control behavior was strongly and independently linked to vegetarian eating.

Funding Source:

University/Hospital:

University of Western Ontario, Canada

Reviewer Comments:

Uneven response rate within schools surveyed
Very small male sample
Ethnicity and socioeconomic factors are not disclosed.

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?	No
	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
	2.4.	Were the subjects/patients a representative sample of the relevant population?	No
	3.	Were study groups comparable?	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
	3.1.	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?	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 or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	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?	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?	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.)	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.)	Yes
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	Yes
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	Yes
	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%.)	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%.)	N/A
	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?	No
	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
	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?	Yes
5.	Was blinding used to prevent introduction of bias?		Yes
	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.)	Yes
	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.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	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?	No
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	No
	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?	N/A
	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
	6.5.	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?	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?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	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?	No
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	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?	No
	8.2.	Were correct statistical tests used and assumptions of test not violated?	No
	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?	No
	8.6.	Was clinical significance as well as statistical significance reported?	No
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	Yes
	9.	Are conclusions supported by results with biases and limitations taken into consideration?	Yes
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	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?	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.	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