Vegetarian Nutrition

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Barr SI, Chapman GE. Perceptions and practices of self-defined current vegetarian, former vegetarian and nonvegetarian women. J Am Diet Assoc. 2002 Mar; 102 (3): 354-360.

PubMed ID: 11902368
 
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:

The purpose of this study was to assess the range of dietary practices among vegetarian women, explore reported changes in vegetarian practices over time and compare perceptions of meat and dairy products among vegetarians, former vegetarians and non-vegetarians.

Inclusion Criteria:
  • Pre-menopausal women
  • 18 to 50 years of age
  • Vegetarian, former vegetarian and non-vegetarian women.
Exclusion Criteria:
  • Men
  • Post-menopausal women
  • Women less than 18 or more than 50 years of age.
Description of Study Protocol:

Recruitment

  • For the quantitative phase of the project a convenience sample of participants were recruited through notices posted in university and community newspapers and word of mouth
  • For the qualitative phase, purposeful sampling procedures were used to recruit participants from the quantitative phase who had a range of eating patterns, vegetarian experiences and personal characteristics.

Design

  • The quantitative phase was a cross-sectional design
  • The qualitative phase included in-depth qualitative interviews. 

Statistical Analysis

  • Quantitative data were analyzed using one-way ANOVA and chi-square tests to examine differences among vegetarians, past vegetarians and non-vegetarians 
  • The in-depth qualitative interviews were audiotaped and transcribed
  • Data analysis included a multistep coding procedure of transcripts, preparation of networks and matrices and writing summary memos to describe the nature and range of issues discussed in each topic.

 

Data Collection Summary:

Quantitative Variables

All variables were assessed using an instrument developed and pilot-tested by the authors and included:

  • Demographics
  • Self-reported vegetarian status
  • Perceptions of meat and dairy products
  • Dietary protein sources (using a modified food frequency questionnaire).

Qualitative Interviews

A semi-structured interview guide averaging about 60 minutes was used to capture:

  • Definitions of vegetarian eating
  • Personal practices, attitudes and rationale relating to various animal products
  • Health beliefs concerning vegetarianism.
Description of Actual Data Sample:
  • Sample (N):
    • Quantitative: 193 women (90 vegetarians, 35 former vegetarians and 68 non-vegetarians)
    • Qualitative: 15 women (three vegan or nearly vegan, five lacto- or lacto-ovo-vegetarian, one pesco-vegetarian, three former vegetarians and three non-vegetarians)
  • Mean age: 31.9 years (SD 8.8 years). No differences for mean age across groups.
  • Ethnicity: 79.4% of sample was White (ethnicity of other 21.6% not provided). Vegetarian women were significantly more likely to be White.
  • Other relevant demographics: No group differences in educational achievement. However highly educated sample as 50% were university graduates and 40% were current university students.
  • Anthropometrics: Not assessed 
  • Location: Assumed to be in the Vancouver, Canada area.

 

Summary of Results:

Consuming Dietary Protein Sources

  • Diets followed by current vegetarians were extremely diverse. Using strict criteria to define groups, six women were vegan, 11 lacto-vegetarian, 22 lacto-ovo-vegetarian, 37 pesco-vegetarian and 14-pollo-pesco vegetarian. However, most vegetarian women (57%) ate chicken and fish occasionally and 17% ate fish or chicken on a weekly basis. 
  • When compared to non-vegetarians and former vegetarians, current vegetarians were less likely to consume flesh foods, less likely to consume eggs and fluid milk at least weekly and more likely to consume all plant protein sources at least weekly.

Table 1: Percent of Diet Group Eating Given Foods on a Weekly Basis

 


 

Vegetarian

(% eat weekly)

Former Vegetarian

(% eat weekly)

Non-Vegetarian

(% eat weekly)

Flesh Foods




Fish

12

65

48

Chicken

5

68

72

Beef

0

40

47

Pork

0

24

26

Diary Products and Eggs


 


 


 

Hard cheese

60

63

54

Yogurt

46

34

54

Eggs

36

57

56

Milk

34

63

57

Cottage cheese

13

18

9

Plant Protein Sources


 


 


 

Beans

74

44

25

Tofu

61

38

19

Nuts

56

43

26

Soy drink

52

11

13

Lentils

48

26

16

Peanut butter

38

21

28

Dietary Change

  • Of the current vegetarians 63% (N=56) reported eating fewer animal products than when they first became vegetarian, 27% (N=24) had not changed and 10% (N=9) included more animal products. Qualitative results indicated that informants became vegetarian by eliminating meat and poultry and then gradually reduced intake of dairy products and eggs as they learned more about vegetarian nutrition and "factory farming."  Those who become less restrictive were concerned about nutritional adequacy and mentioned issues surround convenience and food availability. 
  • Among current vegetarians, the most common planned changes were to use fewer dairy products (N=18) and reduce fat (N=5), fish and seafood (N=5), eggs (N=4) and poultry (N=3). Vegetarian women in the sample indicated that they planned to increase the following foods in their diets:
    • Fruits and vegetables (N=9)
    • Soy products (N=8)
    • Organically grown food (N=6)
    • Beans and legumes (N=4)
    • Seafood (N=2).
  • The most common reasons for former vegetarians to resume an omnivorous diet included:
    • Health reasons (weakness, fatigue, anemia) (N=10)
    • Missing the taste of meat (N=8)
    • Changes in living situation (N=7)
    • Perception vegetarian was too time-consuming (N=6)
    • Specific nutrition concerns (N=5). 
  • Health concerns and lack of social support were the dominant issues described by former vegetarians in the qualitative interviews. 

Perceptions About Meat Products

  • For seven statements concerning the healthfulness or nutrient content of meat, vegetarian responses significantly differed from former vegetarians and non-vegetarians. For four statements about perceptions of possible contaminants (toxins, hormones, antibiotics), responses of vegetarians and former vegetarians were similar and both differed from non-vegetarians' responses.
  • Vegetarians were more likely to emphasize the negative aspects of eating red meat (hormones, antibiotics, additives and environmental contaminants) while non-vegetarians emphasized the positive aspects of eating red meat (red meat is an important part of the diet, it contains important nutrients). These differences were statistically significant at (P<0.001).
  • The qualitative results indicated that about half of the women were concerned both about the nutrient content and the fat and cholesterol in red meat, with differences between diet groups not significant. Poultry and fish were generally perceived to be better choices than red meat. 

Perceptions About Dairy Products

  • Perception about dairy products did not vary consistently by dietary patterns. 
  • The qualitative results also indicated varied beliefs. Almost equal number of participants had positive and negative attitudes about dairy products. Positive aspects included calcium content and reduction of osteoporosis. Negative aspects included high fat, diary industry's treatment of cattle, use of hormones and antibiotics, dairy products are for feeding baby cows not humans  and dairy consumptions causes mucus, bloating and lack of energy. 
Author Conclusion:
  • More than half of the current (self-defined) vegetarians occasionally used fish. This emphasizes the lack of a universally accepted definition for vegetarianism. 
  • Most of the vegetarians seemed to progress along the vegetarian continuum including the use of fewer dairy products over time
  • There was an evident association between beliefs about the nutritional and health attributes of animal products and their consumption. While some beliefs are accurate, other beliefs are misperceptions and not easy to address.
  • The primary limitation is the convenience sample and limits on generalizing the results.
Funding Source:
Industry:
Beef Industry, Canada
Commodity Group:
Reviewer Comments:
  • In addition to the limitation imposed by the convenience sample as acknowledged by the authors, information is lacking regarding the development, pilot testing and validity of the instruments used 
  • It appears as if the food frequency questionnaire only assessed dietary intake over the past week which may not sufficiently capture the range of dietary practices across time
  • A major strength of the study is use of qualitative interviews to further explore the study objectives.
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? No
2. Was the selection of study subjects/patients free from bias? No
  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? 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.) N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? 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? N/A
4. Was method of handling withdrawals described? N/A
  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? N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  5. Was blinding used to prevent introduction of bias? 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? N/A
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? 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? No
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? ???
  7.2. Were nutrition measures appropriate to question and outcomes of concern? ???
  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? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  7.5. Was the measurement of effect at an appropriate level of precision? No
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? N/A
  8.6. Was clinical significance as well as statistical significance reported? N/A
  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