Vegetarian Nutrition

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Worsley A, Skrzypiec G. Teenage vegetarianism: Beauty or the beast? Nutrition Research. 1997; 17 (3): 391-404.

 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To examine the likely cognitive and social ideological influences associated with teenage vegetarianism.

Inclusion Criteria:

Students in Class 10 in South Australian schools.

Exclusion Criteria:

Surveys with too many blank or inconsistent answers.

Description of Study Protocol:

Recruitment

Students were selected from South Australian secondary schools that had been randomly selected according to the socioeconomic (SES) characteristics of the regions in which they were located.

Design

  • Areas in South Australia were identified based on SES criteria (four clusters, ranked low to high). Schools were then randomly selected within these clusters. If a school did not participate, another school from the cluster was randomly selected.
  • Both government and non-government schools were selected to get an approximately equal number of subjects from each type of school
  • Class of Year 10 students (approximately 16 years of age) were selected and given an in-class anonymous survey
  • More than 2,000 students from 52 schools were surveyed.

Blinding Used

Student responses were anonymous and self-administered independently in class and then placed into sealed envelopes for the researchers.

Intervention

None.

Statistical Analysis

  • Simple frequency analyses were done on the reported vegetarian behaviors and contingency table analyses were used to compare the reported behaviors and attitudes of key groups of respondents
  • Analyses of variance were used to compare the means of factor scores derived from principal components analysis of the respondents’ attitudes about meat and vegetarianism
  • Discriminant analysis was used to identify the main vegetarian attitudes items that discriminated between vegetarian and non-vegetarian females
  • Significance was set at P<0.05.
Data Collection Summary:

Timing of Measurements

  • One-time survey conducted in 1994
  • A vegetarianism questionnaire contained items concerning the respondents’ experiences of vegetarianism in the past and present, their views for and against it and the support expected from others. The vegetarian questionnaire was part of one of two booklets of questions which had been designed to examine media and ideological influences on young people’s eating and dieting habits.
  • Answers to questions in the booklets (with the exception of the food intake questions) were measured using a Likert scale design.

Dependent Variables

Vegetarianism: Self-reported vegetarian status was used to classify teenagers as full or semi-vegetarians or non-vegetarians. Students responded to the question “Are you a Vegetarian?” by answering "No," "Semi-" or "Yes."

Independent Variables

  • Food consumption: A list of 36-foods based on Baghurst’s (15) food frequency questionnaire was used as a self-reported measure of food consumption
  • Attitudes about foods: A series of questions about a variety of foods were developed by the researchers and used to examine adolescents’ attitudes to foods
  • Dieting behavior: Two separate measures of dieting behavior were used
    • Stunkard and Messick’s (16) “Three-factor Eating Questionnaire,” which measures restraint, disinhibition and hunger
    • Benbrook’s (17) “Body Weight Control” questionnaire.
  • Appearance: Adolescents’ views of the importance of appearance were examined using a modified version of Hall et al’s (18) “Food, Fitness and Looks Questionnaire”
  • Gender: Smith and Walker’s (19) “Women in Society Questionnaire” was adapted and made suitable for the teenage respondents of both sexes and used to examine their views of gender roles
  • Media: Adolescents’ views of television were examined through a series of questionnaire items derived through prior interviews
  • Environmental attitudes: A modified version of Herrera’s (21) “Questionnaire of Environmental Beliefs”
  • Vegetarian views and experiences: A series of questions based on research done by Wright and Howcroft (22) on both adult and teenage vegetarians.
Description of Actual Data Sample:
  • Initial N: Surveys from more than 2,000 students were collected
  • Attrition (final N): Only adolescent girls' responses were used. N=825 females.
  • Age: Approximately 16 years at the time of the survey (school class 10)
  • Ethnicity: Not reported
  • Other relevant demographics: SES used as a control variable
  • Anthropometrics: None reported
  • Location: South Australia.
Summary of Results:

The authors found that adolescent female vegetarians are quite different from adult vegetarians.

  • Vegetarian attitudes among teen girls is complex, sharing some of the ideological concerns of adult vegetarians, while at the same time incorporating elements that may not be as prevalent in adult vegetarians (such as a concern with body image and fashion)
  • Because chicken was frequently consumed by female full and semi-vegetarians, the predominant concern with the welfare of animals as a motivation for vegetarianism may not extend beyond four-legged animals
  • Adolescent female vegetarians placed more emphasis on weight control, concern with body appearance, fashion and the media than non-vegetarians. It is unclear whether vegetarianism is simply chosen more often by young females with eating disorders or whether vegetarianism could be stage in the development of eating disorders.

The authors tested a series of hypotheses regarding ideological influences on adolescent vegetarians (who were overwhelmingly female in this study).

Food Consumption

  • Does self-reported vegetarianism (full or semi-) translate into actual differences in food intake?
  • Female vegetarians and semi-vegetarians were less likely to consume whole milk (P<0.01) and meat (not counting chicken; P<0.001) and more likely to consume legumes (P<0.01) and chicken or rice (P<0.05). So, while female vegetarians were less likely to consume most meats, as a group (full and semi-vegetarians combined) they were more likely to consume chicken and still think of themselves as vegetarians.

Views of Food

  • Hypothesis One: Adolescent vegetarians would hold different views of foods to non-vegetarians, positive views of fruit and vegetables and negative views of meats
  • Findings: Anti-meat attitudes were strongest among vegetarian teenage females (P<0.001). They were also more pro-vegetables (P<0.001), pro-fruit (P<0.001) and more likely to practice meat restraint (P<0.001).
  • Conclusion: Hypothesis One is supported. Teen female vegetarians have quite different views of food than their non-vegetarian counterparts.

Dieting Behavior

  • Hypothesis Two: Vegetarian women would be less likely to diet to lose weight than would non-vegetarian girls
  • Findings: Female full and semi-vegetarians reported very different dieting behaviors than their non-vegetarian female peers. They scored significantly higher on the dieting action score (P<0.001), exhibited greater restraint (P<0.001), less disinhibition (P<0.05), reported less hunger (P<0.05) and exhibited both mild (P<0.001) and extreme (P<0.001) dieting behaviors.
  • Conclusion: The hypothesis is refuted. Female adolescent vegetarians are more likely to use dieting behaviors than their non-vegetarian peers. The authors speculate that the claim to be “vegetarian” may actually serve as a cover (a justification) for dietary habits that might otherwise be viewed negatively by their peers and family.

Appearance

  • Hypothesis 3A: Teenage vegetarians should express less interest in body appearance and fashion than their same-sex peers
  • Hypothesis 3B: Teenage vegetarians should show less interest in television than their same-sex peers
  • Findings: Compared with non-vegetarian females, female adolescent vegetarians were more conscious of their appearance (P<0.001). Additionally, female vegetarians were less likely to rely on television for relaxation and entertainment, but were more likely to use television as a source of reference for their appearance and behavior (significance not reported).
  • Conclusion: Both hypotheses 3A and 3B were refuted. Female vegetarian teens were more concerned with body appearance and fashion than their non-vegetarian peers. Additionally, they exhibited more interest in television as a reference point for fashion and behavior than non-vegetarians.

Gender Equity

  • Hypothesis Four: Vegetarians are likely to hold more egalitarian views of gender than non-vegetarians
  • Findings: Female adolescent vegetarians were significantly less supportive of traditional patriarchal attitudes (P<0.01) and more supportive of gender equality attitudes (P<0.01) than their non-vegetarian peers
  • Conclusion: Female teen vegetarians were more likely to hold egalitarian views of gender than non-their vegetarian peers.

Interest in the Environment

  • Hypothesis Five: Vegetarians would express more interest in environmental issues and animal welfare than would non-vegetarians
  • Findings: Concern with environmental protection was the main concern of adolescent female vegetarians, but this was the only factor in which they differed significantly from non-vegetarians (P<0.01). Indeed, more than one-third of non-vegetarians expressed concern about animal cruelty, but did not translate this concern into dietary behaviors.

  • Conclusions: This supports the hypothesis of more interest among female vegetarians in environmental issues. But this is only one among a cluster of related issues (treatment of animals being another) and was the only issue about which female vegetarians differed significantly from their peers.
Author Conclusion:
  • Adolescent vegetarianism is largely a female phenomenon characterized by meat avoidance, concern for the environment, animal welfare, gender equity, weight-loss behaviors and high concern with body appearance
  • There was a strong association between adolescent vegetarianism and extreme weight-loss behaviors, which may be indicative of eating disorders. This requires further investigation.
Funding Source:
Government: MRC Australia
Reviewer Comments:

Report of methods in this article was very limited. However, because this article was the outcome of a larger study, the methods of data collection were reported elsewhere. Otherwise, this article would not have received a positive quality rating.

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? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  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) 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? 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
  3.3. 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")? 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. Was method of handling withdrawals described? No
  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%.) No
  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? No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  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? 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? 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? 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
  6.5. 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? Yes
  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
  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? 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? 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
  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? 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? 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