Vegetarian Nutrition

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Perry CL, McGuire MT, Neumark-Sztainer D, Story M. Characteristics of vegetarian adolescents in a multiethnic urban population. J Adolesc Health. 2001 Dec; 29 (6): 406-416.

PubMed ID: 11728890
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To examine the prevalence of adolescents’ vegetarianism in a multi-ethnic urban population and its relation to demographic, personal, weight-related and behavioral factors.

Inclusion Criteria:
  • Adolescents aged 11 to 18 years old
  • Attending middle and high schools in the Twin Cities area of Minnesota.
Exclusion Criteria:

Not described.

Description of Study Protocol:
  • Recruitment: Middle and high schools within health, physical education and science classrooms in the Twin Cities area of Minnesota
  • Design: Cross-sectional comparison study. Self-report surveys and anthropometric assessments within the 1998-1999 school year.
  • Blinding used: Not described
  • Intervention: Not applicable.

Statistical Analysis

  • Logistic regression analyses controlled for variables with random effects
  • Confidence intervals
  • Odds ratio.
Data Collection Summary:

Timing of Measurements

  • One time self-reported questionaire and anthropometric data were collected from a representative sample of 4746 adolescents from 31 public middle schools and high schools in the Twin Cities area of Minnesota
  • Students answered questions concerning vegetarianism, food and weight and health behaviors
  • Height and weight were directly measured.

Dependent Variables

  • Meeting the Healthy People 2010 criteria
  • Weight-related behaviors by gender among vegetarian and non-vegetarian adolescents:
    • Percentage who weigh themselves frequently
    • Percentage who reported using at least one healthy weight-control behavior in the past year
    • Percentage who reported using at least one unhealthy weight-control behavior in the past year
    • Percentage who reported vomiting for weight reasons in the past week.

Independent Variables

  1. Vegetarian
    • Semi-vegetarian (chicken or fish)
    • Restricted vegetarian: Lacto-vegtarian (dairy), ovolacto-vegetarian (eggs, dairy), vegan (no eggs, dairy, chicken or fish).
  2. Non-vegetarian.

Control Variables

  • Gender
  • Age
  • Race.
Description of Actual Data Sample:
  • Initial N: Vegetarian (N=262) and non-vegetarians (N=4258) (50.2% males, 49.8% females)
  • Attrition (final N): 77.1%
  • Age: 11 to 18 years old (mean age of 14.9 years old).

Ethnicity

  • Caucasian: 48.5%
  • African-American: 19.0%
  • Asian-American: 19.2%
  • Hispanic: 5.8%
  • Native American: 3.5%
  • Mixed or Other: 3.9%.

In the Vegetarian Group, nearly three-fourths (73.7%) were female. Nearly half (47.5%) of the vegetarians were white, 26.8% were Asian, 11.1% were black, 5.8% were Hispanic, 5.0% were American Indian, while the remaining 4% were Hawaiian or Pacific Islander or Other.

*Only the Caucasian, African-American and Asian-American participants were included in the analysis).

Other Relevant Demographics

34.3% were in junior high school and 65.7% in high school.

Anthropometrics

  • BMI, 85th to 95th percentile: 19 restricted vegetrians, 12 semi-restricted vegetarians
  • 95th percentile or higher: Seven restricted vegetrians, 11 semi-restricted vegetarians.

Location

Twin Cities area, Minnesota.

Summary of Results:
  • Statistics were calculated with unadjusted means and odds ratios and 95% confidence intervals adjusted for school and gender
  • Comparisons were done using an odds ratio.

Comparisons of Restricted Vegetarians and Semi-Vegetarians on Demographic, Personal, Weight-Related and Behavioral Factors

  Restricted Vegetariansa
N=94
Semi-Vegetariansb
N=158
OR 95% CI
Demographic Factors Females
80.9 (76)
68.9 (109)
1.91
1.03, 3.54*
Asian
18.1 (17)
32.5 (51)
0.46
0.24, 0.89*
Black
4.3 (4)
14.0 (22)
0.23
0.07, 0.72*
High school
58.5 (55)
62.6 (97)
0.45
0.23, 0.88*
SES (mean ±SD)
3.5±1.4
2.7±1.4
1.41
1.15, 1.73**
Years of vegetarianism (>2)
52.1 (49)
38.8 (61)
1.90
1.12, 3.25*
Reasons Why Vegetarian Not kill animals
45.7 (43)
18.9 (30)
3.19
1.79, 5.71**
Weight-Related Factors Healthy weight-control practice
in the past year
80.8 (76)
92.9 (146)
0.32
0.14, 0.71**
Unhealthy weight-control
practice in the past year
57.4 (54)
75.2 (118)
0.44
0.25, 0.77**
Physical Activity Vigorous (>2 hours per week)
57.4 (54)
37.3 (59)
2.38
1.38, 4.06**
Moderate(>2 hours per week)
52.1 (49)
37.9 (60)
1.82
1.07, 3.07*
BMI:
85th-95th percentile
21.8 (19)
9.2 (12)
2.03
1.05, 3.91*

Demographic, Personal, Weight-Related and Behavioral Factors of Adolescent Subjects

  Vegetarians
N=262
Non-Vegetariansa
N=4,258
OR 95% CI
Demographic Factors Females
73.7(193)
48.4 (2062)
2.95
2.23, 3.92***
Black
11.1 (29)
18.2 (767)
0.53
0.35, 0.79**
High school
61.4 (159)
65.2 (2,750)
0.51
0.32, 0.81**
SES (mean ±SD)
3.1±1.4
2.9±1.3
1.10
0.99, 1.22
How Much do You Care About Eating healthy
85.5 (224)
78.4 (3,321)
1.43
1.00, 2.04*
Being healthy
83.7 (215)
89.9 (3,790)
0.55
0.39, 0.78***
Self-efficacy scale
56.1 (147)
46.3 (1,971)
1.50
1.16, 1.94**
I weigh myself often
40.0 (102)
31.3 (1,317)
1.34
1.03, 1.74*
Diagnosed eating disorder
8.5 (22)
3.1 (131)
2.72
1.71, 4.34***
Body satisfaction scale
41.2 (108)
53.2 (2,265)
0.74
0.57, 0.96*
Healthy weight-control
practice in the past year
87.7 (228)
76.9 (3,249)
1.75
1.19, 2.57**
Unhealthy weight-control
practice in the past year
68.5 (178)
43.7 (1,848)
2.33
1.77, 3.08***
Vomited in the past week
8.3 (21)
2.5 (106)
2.99
1.86, 4.79***
Diet pills in the past week
5.6 (14)
2.0 (83)
2.37
1.35, 4.17***
Laxatives in the past week
5.6 (14)
 
 
 
0.7 (30)
 
 
 
7.52
 
 
 
4.11, 13.8*** 
 
 
Behavioral factors Thought about killing yourself
34.7 (82)
24.9 (1,009)
1.37
1.03, 1.82*
  Ever tried to kill yourself
18.3 (44)
8.6 (348)
2.04
1.53, 2.88***

Vegetarian vs. Non-Vegetarian

  • Vegetarians were nearly three times more likely to be female than were non-vegetarians
  • There was a significantly lower percentage of blacks among the vegetarians than among non-vegetarians
  • Vegetarians were less likely than non-vegetarians to be in high school rather than in junior high or middle school
  • Vegetarians were significantly more likely to care about eating healthy food and less likely to care about being healthy
  • Vegetarians had greater self-efficacy to be able to eat healthy foods in a variety of situations than did non-vegetarians
  • Vegetarians were more likely to weigh themselves often, to have been told by a doctor that they had an eating disorder, to be dissatisfied with their bodies and to practice healthy and unhealthy weight-control behaviors
  • Vegetarians were more likely than non-vegetarians to have thought about or actually tried to kill themselves.

* Other measures of substance use, depression, physical activity and all levels of BMI were not different between groups.

Vegetarian and Gender

  • Vegetarian males weigh themselves more frequently then non-vegetarian males
  • Among males, vegetarians engage in healthy weight-control behaviors more than non-vegetarians
  • Among both males and females, vegetarians engage in more unhealthy weight-control behaviors than their non-vegetarian counterparts
  • Among males and females, vegetarians are more likely to vomit than their non-vegetarian counterparts.

Vegetarian and Race

  • Among Asians and blacks, vegetarians were more likely to report having been diagnosed with an eating disorder than non-vegetarian Asians and blacks
  • Among vegetarians, Asians and blacks reported higher rates of being diagnosed with an eating disorder than whites.

Non-Vegetarian and Race

Asians reported more, and blacks reported less depressive symptomatology than whites.

* This was not found among vegetarians.

Semi-Vegetarian (Eating Chicken or Fish) vs. More Restrictive (Vegans, Lactovegetarians and Ovolactovegetarians)

  • Semi-vegetarians were less likely to be female and more likely to be Asian and black than the more restricted vegetarians
  • The semi-vegetarians were more likely to be in high school, come from a lower SES and to have been vegetarians for a shorter period of time
  • Restrictive vegetarians were 3.19 times more likely than semi-vegetarians to say they were semi-vegetarians because they did not want to kill animals
  • The semi-vegetarians were more likely to engage in healthy and unhealthy weight-control practices and less likely to be physically active
  • The semi-vegetarians were much less likely to be at risk for overweight than the more restricted vegetarians
  • "Male vegetarians might need added information, screening or counseling to assure a healthful diet. To our knowledge, ours is the first study to have demonstrated this increased risk among adolescent male vegetarians, most likely because other studies focused on females or had too small a sample size of males to observe these interactions."
  • "…the restricted vegetarians (e.g. vegans, lacto- and lacto-ovo vegetarians) appear to be more 'stable' and healthy adolescent vegetarians, with over half having been vegetarian for over 2 years, and with less involvement in unhealthy weight control behaviors."
  • "Semivegetarians (63% of the vegetarians) may be a group who are more likely to be experimenting with vegetarianism as another form of weight control practice, and therefore are an important group to consider when planning intervention programs to prevent unhealthy weight control behaviors and eating disorders."

Two Distinct Groups of Vegetarian Teens Based on Motivation

  1. Vegetarian: Concern for animals
  2. Semi-vegetarians: Concern about weight (over twice as likely to be overweight).
Author Conclusion:

Adolescent vegetarians are at greater risk than others for involvement in unhealthy and extreme weight control behaviors. Vegetarian males are at particularly high risk. Vegetarianism among adolescents may therefore be a signal for preventive intervention. Adolescents who choose to become vegetarians may also need to learn how to healthfully do so.

Funding Source:
University/Hospital: U of Minnesota
Reviewer Comments:
  • Self-reporting of vegetarianism
  • Cross-sectional design.
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
  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
  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) 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. 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? 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? 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? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  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? N/A
5. Was blinding used to prevent introduction of bias? N/A
  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? N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  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? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  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? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  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