EAL

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine whether adolescent vegetarians were more likely than non-vegetarian peers to meet the dietary recommendations of the Healthy People 2010 objectives
To examine differences in other nutrients between these two groups.

Inclusion Criteria:

Adolescents, aged 11 years to 18 years
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 the Twin Cities area of Minnesota.

Design

Cross-sectional comparison study
Self-report surveys and anthropometric assessments within the 1998 to 1999 school year.

Intervention

Not applicable.

Statistical Analyses

Logistic or linear regression analyses
Confidence intervals
Odds ratios.

Data Collection Summary:

Timing of Measurements

One-time self-reported questionnaire and anthropometric data were collected from a representative sample of 4,746 adolescents from 31 public middle schools and high schools in the Twin Cities area of Minnesota.

Dependent Variables

Meeting the Healthy People 2010 criteria.

Independent Variables

Vegetarian
Semi-vegetarian (diet includes chicken or fish)
Lactovegetarian (diet includes dairy)
Ovolactovegetarian (diet includes eggs and dairy)
Vegan (diet excludes eggs, dairy, chicken and fish)
Non-vegetarian.

Control Variables

Sex
Age
Race.

Description of Actual Data Sample:

Initial N: Vegetarians (N=262) and non-vegetarians (N=4,258); 50.2% male, 49.8% female
Attrition (final N): 81.5% completed
Age: 11 years to 18 years old; mean age was 14.9 years.

Ethnicity

White: 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. Almost 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 and the remaining 4% were Hawaiian or Pacific Islander or other. (Only the white, African-American and Asian-American participants were included in the analysis.)

Other Relevant Demographics

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

Anthropometrics

BMI in the 85th percentile to 95th percentile
- N=19 restricted vegetarians
- N=12 semi-restricted vegetarians.
BMI in the 95th percentile or higher
- N=7 restricted vegetarians
- N=11 semi-restricted vegetarians.

Location

Twin Cities area, Minnesota.

Summary of Results:

Differences in Selected Dietary Factors Between Vegetarians and Non-Vegetarians

Dietary Factor	Vegetarian (N=262)	Non-vegetarian (N=4,259)	P-Value
Calories, kcal	1,972.9 (81.0)	2,092 (19.8)	0.15
Protein, g	70.0 (2.9)	75.3 (0.7)	0.08
Calcium, mg	1,070.4 (43.4)	1,089.7 (10.6)	0.67
Zinc, mg	1.4 (0.5)	11.7 (0.1)	0.54
Iron, mg	16.1 (0.6)	14.7 (0.1)	0.03
Vitamin A, U	9,931.1 (448.1)	8,480.4 (109.8)	0.002
Vitamin B₆, mg	1.7 (0.1)	1.7 (0)	0.94
Vitamin B₁₂, mcg	6.3 (0.4)	7.2 (0.1)	0.02
Vitamin C, mg	157.0 (6.8)	149.4 (1.7)	0.27
Folate, mcg	348.8 (13.2)	307.9 (3.2)	0.003
Linoleic acid, g	10.9 (0.5)	11.8 (0.1)	0.15
Cholesterol, mg	186.0 (9.6)	221.7 (2.3)
Caffeine, g	53.2 (2.9)	43.6 (0.7)	0.001
Fiber, g	18.8 (0.7)	16.1 (0.2)
Regular Soda, Daily Servings	1.2 (0.1)	1.4 (0)	0.004
Diet Soda, Daily Servings	0.3 (0)	0.1 (0)
Fruit Drink, Daily Servings	0.4 (0)	0.5 (0)	0.02
Fast Food, Times in Past Week	1.9 (0)	2.1 (0)	0.001
Percentage of Calories from Protein	13.7 (0.2)	14.3 (0)	0.01
Percentage of Calories from Carbohydrate	60.9 (0.6)	56.4 (0.1)
Percentage of Calories from Total Fat	26.9 (0.4)	30.1 (0.1)
Percentage of Calories from Saturated Fat	9.3 (0.1)	10.7 (0)
Percentage of Calories from Polyunsaturated Fat	5.4 (0.1)	5.7 (0)	0.02
Percentage of Calories from Monounsaturated Fat	10.0 (0.1)	11.4 (0)
Servings of Fruit	2.7 (0.1)	2.3 (0)	0.003
Servings of Vegetables	2.4 (0.1)	1.9 (0)
Servings of Fruits and Vegetables	5.1 (0.2)	4.2 (0)

Percentages of Adolescents Who Met Healthy People 2010 Objectives by Vegetarian Status

Healthy People 2010 Objective		Vegetarian, % (N=262)	Non-vegetarian, % (N=4,259)	OR (95% CI)
Fat Intake	<30% of calories from fat	69.5	47.5	2.34 (1.74-3.14)
Fat Intake	<10% of calories from saturated fat	65.0	39.0	2.62 (1.97-3.48)
Calcium Intake	>1,300 mg	29.7	35.0	0.93 (0.69-1.25)
Fruit and Vegetable Intake	>2 servings of fruit	54.2	45.3	1.42 (1.07-1.88)
	>3 servings of vegetables	26.4	13.9	2.16 (1.56-2.98)
	>3 servings of vegetables of which at least one is deep yellow or green	19.1	9.6	2.12 (1.53-2.95)
	>5 servings of fruits or vegetables	38.9	28.1	1.56 (1.17-2.09)
Grain Intake	>6 servings of grains	42.2	40.3	1.19 (0.91-1.57)

Percentages of Specific Types of Adolescent Vegetarians Who Met Healthy People 2010 Objectives

Healthy People 2010 Objective		Ovolactovegetarian, % (n=94)	Semi-vegetarian, % (n=158)	OR (95% CI)
Fat Intake	<30% of calories from fat	79.5	64.1	2.02 (1.06-3.87)
Fat Intake	<10% of calories from saturated fat	71.1	62.6	1.38 (0.76-2.52)
Calcium Intake	>1,300 mg	34.8	26.4	1.49 (0.83-2.65)
Fruit and Vegetable Intake	>2 servings of fruit	64.6	46.8	2.17 (1.21-3.87)
	>3 servings of vegetables	31.7	22.6	1.65 (0.87-3.12)
	>3 servings of vegetables of which at least one is deep yellow or green	21.3	17.1	1.29 (0.67-2.50)
	>5 servings of fruits or vegetables	50.0	30.6	2.36 (1.31-4.24)
Grain Intake	>6 servings of grains	44.7	40.0	1.26 (0.72-2.22)

Vegetarian and Diet

Vegetarian adolescents were significantly more likely than non-vegetarian adolescents to meet the Healthy People 2010 objectives
This was particularly noteworthy for total fat (70% vs. 48%), saturated fat (65% vs. 39%), daily servings of vegetables (26% vs. 14%) and daily intake of five or more servings of fruits and vegetables (39% vs. 28%)
Vegetarian adolescents were more than twice as likely to eat less than 30% of their calories from fat and nearly three times more likely to eat less than 10% of their calories from saturated fat. They were also 1.4 to two times more likely to eat two or more servings of fruit; three or more servings of vegetables; three or more servings of vegetables, including one that is dark yellow or green; five or more servings of fruits and vegetables daily.
Vegetarians were also less likely to eat fast food or drink regular soda and fruit drinks
Vegetarians consumed less vitamin B₁₂, more diet soda, more caffeine and more iron.

Vegetarian vs. Non-Vegetarian

Vegetarian adolescents, compared with non-vegetarian adolescents, consumed significantly less vitamin B₁₂, cholesterol, regular soda, fruit drink and fast food, as well as a lower percentage of calories from protein and all types of fat
Vegetarians were significantly more likely than non-vegetarians to consume more iron, vitamin A, folate, caffeine, fiber and diet soda, as well as a greater percentage of calories from carbohydrates and more servings of fruit and vegetables.

Vegetarian and Race

There was a significant difference between vegetarians and non-vegetarians in the sex and racial makeup of the samples.

Semi-Vegetarian vs. Non-Vegetarian

Ovolactovegetarians were more than twice as likely as semi-vegetarians to eat less than 30% of the calories in their diet from fat, more than two servings of fruit per day and five or more servings of fruits and vegetables per day
Comparing ovolactovegans with semi-vegetarians, there were no interactions between adherence to the Healthy People 2010 objectives by sex, but there were five significant interactions by race
Although semi-vegetarians were significantly less likely than white ovolactovegetarians to meet the daily requirement for calcium [22.6% vs. 43.9%; odds ratio (OR), 0.37; 95% confidence interval (CI), 0.16-0.82], to eat more than two servings of fruit each day (34.5% vs. 68.6%; OR, 0.24; 95% CI, 0.11-0.54), to eat more than three servings of vegetables each day (8.6% vs. 35.3%; OR, 0.17; 95% CI, 0.06-0.49), to eat more than three vegetables each day, including on deep yellow or green vegetables (6.2% vs. 22.8%; OR, 0.22; 95% CI, 0.07-0.74) and to eat six or more servings of grains each day (30.0% vs. 53.7%; OR, 0.36; 95% CI, 0.17-0.79).

Author Conclusion:

Adolescent vegetarians have a dietary pattern that is more likely to meet the Healthy People 2010 objectives than the dietary pattern of adolescent non-vegetarians.

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?	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)?	No
	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)?	No
	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