Vegetarian Nutrition

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Worsley A, Skrzypiec G. Teenage vegetarianism: prevalence, social and cognitive contexts. Appetite. 1998 Apr; 30(2): 151-170.

PubMed ID: 9573450
 
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 measure the prevalence of teenage vegetarianism and associated food habits and beliefs.

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, which 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 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, which discriminated between vegetarian and non-vegetarian females
  • Significance 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 that 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: (1) Stunkard and Messick’s (16) “Three-factor Eating Questionnaire” which measures restraint, disinhibition and hunger, and (2) 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”
  • Sex: 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.

Control Variables

  • Sex
  • SES

 

Description of Actual Data Sample:

Initial N: Surveys were collected from more than 2,000 students

Attrition (final N): For the analyses, responses from 536 females and 416 males were used. The actual N used differed slightly depending on the analysis (depending on the number of usable responses).

Age: Approximately age 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:

Prevalence of Teenage Vegetarianism and Semi-vegetarianism

The prevalence of vegetarianism depended on how vegetarianism was defined and understood. The authors found that for teenagers, vegetarianism is not an all-or-nothing affair.

The study found that 8% to 10% of girls do not eat red meat (or eat it very rarely) and consider themselves vegetarian. This contrasts to 1% to 2% of teen boys. Few adolescents were vegans.

Self-reports indicated that many teens did not know whether to classify themselves as vegetarian or not, and meat-eating or -avoiding habits varied. As the Table shows, teens restricted meat in various ways (not eating red meat, not eating other meats) and to varying degrees. Although almost all ate meat occasionally, some were more restrictive in their meat intake than others were. When asked to define whether they were vegetarian, these variations in practice lead to some confusion. As the difference between Q1 and Q2 (different ways of asking the same question on the survey), when teens were given only yes/no options, some who occasionally ate meat classified themselves as vegetarian while others who restricted meat (and so might be considered some type of vegetarian) answered “no.”

In short, whether teens think of themselves as vegetarian depends on how they understand meaning of the term.

 
Response
% Females
% Males
Q1: Are you currently a vegetarian? (yes/no)
Yes
8
3
Q2: Are you a vegetarian (yes, no, semi-vegetarian)
 
Yes: 5
Semi: 16
Yes: 1
Semi: 6
Meat Consumption Categories
Vegetarian
Consume all meats <2 times in 2 months
8
1
Quasi-vegetarian
Consume all meats <5 times in 2 months
24
10
Pollo-vegetarians
Consume red meat <2 times in 2 months
10
2
Quasi-pollo-vegetarians
Consume red meat <5 times in 2 months
27
10

Although definitions of vegetarianism varied, one thing was clear: namely, among teenagers, vegetarianism is largely a feminine phenomenon. Even though at most approximately one fourth of the girls could be considered some type of meat restrictor (if not vegetarian outright), 40% of the sample indicated that they had thought about it.

Vegetarian Associates and Social Support

The gendered nature of teenage vegetarianism was also evident in the characteristics of teens’ social networks.

Girls claimed to know more vegetarians than boys did (almost half of them knew two or three and one in six knew between four and eight vegetarians, although fewer than 3% of the girls had immediate family members who were vegetarian.

Female vegetarians expected support from their mothers (78%) and their best female friend (67%) followed by their boyfriends, classmates and older sisters. Fathers, older brothers, other relatives and neighbors offered less support or outright opposition.

Food Intakes

Consistent with their self concepts, vegetarians and semi-vegetarians were significantly less likely to consume all kinds of meat, except fish, than were non-vegetarians. Fish was the only flesh food listed for which there was no significant difference between vegetarians (43%) and non-vegetarians (41%).

Additionally, vegetarians and semi-vegetarians ate oranges, rice, low-fat milk, carrots, beans/soybeans/lentils and lettuce more often than did non-vegetarians.

Reasons For and Against Being Vegetarian

Teens were asked to respond to several questions about their attitudes and beliefs (not all explicitly dealing with food). The authors carried out a principal components analysis to identify factors to account for reasons for being or not being vegetarian. They found that five groups of variables explained 63.1% of the variance:

  1. Meat acceptance: this factor emphasizes the willingness of many of the students to separate the images of the living animal from its slaughter
  2. Meat production is bad: this factor deals with the perceived evil effects ad immorality of meat production
  3. Meat is hard to avoid: this factor included items that indicated that meat was part of the social and physical environment (at school, at home, with friends)
  4. Pro-vegetarian influences: this factor comprised items indicating pro-vegetarian family, friends, religious beliefs (and not liking the taste of meat)
  5. Pro-meat influences: similarly, this factor indicated pro-meat surroundings and preferences
  6. On these factors, vegetarian women were most different from teen boys and non-vegetarian girls were in the middle.

Vegetarian girls:

  • Tended to deny that meat is acceptable (P<0.0001)
  • Agree that meat production is bad (morally wrong or hurts the environment) (P<0.0001)
  • Disagree that meat eating is difficult to avoid (P<0.0001)
  • Dismiss pro-meat influences (P<0.0001)
  • Fewer agreed that “meat is good for health” or that they “like meat too much”.

As many as one third of teenage girls have difficulty divorcing the image of the living animal and its slaughter from meat products. They seem to have different understandings of both meat and animals than do non-vegetarians.

Different World Views

The difference between vegetarians and non-vegetarians was not simply a matter of whether or not to eat meat or how to view animals. Rather, the authors argue that teen vegetarians generally held widely different world views when compared with their non-vegetarian classmates. For instance, vegetarians:

  • Were both more concerned and more pessimistic about environmental issues
  • Placed less trust in scientific solutions to environmental problems
  • Valued equality more in relationships between sexes
  • Were more concerned about being slim
  • Tended to restrict their energy intake more
  • Were more likely to look to television for behavioral guidance.

According to the authors, teenage vegetarians and non-vegetarians seemed to live in different worlds. Whether this is because of different personal values or different personality traits is unclear and needs further research.

 

Author Conclusion:
  1. Self-reported vegetarianism was more common among teenage women. Approximately one fourth can be considered to be at least partially vegetarian.
  2. Social support for vegetarianism was greater among teenage women than among boys—vegetarianism seemed to be a feminine phenomenon.
  3. Vegetarian beliefs substantially predicted vegetarian habits, particularly beliefs about the animal origin of meat, health and taste consequences of meat ingestion and avoidance.
  4. More research is required into ideological associations of adolescents’ vegetarian beliefs and practices.

 

Funding Source:
Government: National Health and Medical Research Council, Australia
Reviewer Comments:

This survey was the basis for more than just this article. Student demographics are not presented in this article.

The research design was oriented toward capturing a representative sample.

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? 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")? 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? 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? 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? 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? 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