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 investigate the degree of individual heterogeneity in diet-mixing behavior and examine the associations of different dietary compositions with selected demographic characteristics.

Inclusion Criteria:

Females
Age 15 to 49 years
Ever-married marital status
Residents of 26 states in six regions of India
Completion of the 1998 to 1999 National Family Health Survey (NFHS-2).

Exclusion Criteria:

None specified.

Description of Study Protocol:

Recruitment

Data from the NFHS-2 survey was analyzed for food frequency patterns and demographic characteristics.

Design

Analysis of the individual responses to the dietary questions asked on NFHS-2

Respondents were interviewed and asked to rate their frequency of consumption (daily, weekly, occasionally, never) of specific food items:
- Milk or curd
- Pulses or beans
- Green leafy vegetables
- Other vegetables
- Fruits
- Eggs
- Chicken, meat or fish
Coding of responses according to frequency of consumption
Identification and ordering of dietary classes:
- Very high mixed-diet
- High mixed-diet
- Moderate mixed-diet
- Low mixed-diet
- Very low mixed-diet
Labeling of the identified classes into clusters according to diet mixing patterns:
Non-vegetarian
- Very high mixed-diet
- High mixed-diet
- Moderate mixed-diet
Vegetarian
- Low mixed-diet
- Very low mixed-diet
Analysis of these clusters for association with selected categorical variables.

Blinding Used

Not applicable.

Intervention

Not applicable.

Statistical Analysis

The authors used statistical procedures to identify groups based on diet intake rather than pre-define diet groups. They used the following procedures to identify diet groups:

Latent class analysis
Multinomial logistic regression.

Data Collection Summary:

Timing of Measurements

NFHS-2 was conducted between November 1998 and March 1999.

Dependent Variables

Membership in one of five latent class dietary clusters:

Very high mixed-diet
High mixed-diet
Moderate mixed-diet
Low mixed-diet
Very low mixed-diet.

Independent Variables

Demographic characteristics including:

Spatial
- Place of residence
- Region of country
Socio-economic and cultural
- Standard of living
- Education
- Religion
- Ethnicity
- Type of employment
Interaction effects.

Control Variables

Variables controlled during regression analyses:

Current age of respondent
Children below five years of age in the household
Respondent's current pregnancy status.

Description of Actual Data Sample:

Initial N: 90,303 females
Attrition (final N): 90,180 females with complete survey responses
Age: 15 to 49 years
Ethnicity: Indian
Other relevant demographics: Ever-married females; living in 26 states in India (comprising 99% of India's total population)
Anthropometrics: None reported
Location: Survey performed in India.

Summary of Results:

Identifying Dietary Classes According to Intake Patterns

The authors used dietary intake data, rather than predefined diet categories, to partition Indian women into diet groups. In other words, they relied on dietary intake similarities rather than respondents' definition of their diet as “vegetarian” or “non-vegetarian” to create five classes of diets. They labeled these diet classes according to the combination (or “mixing”) of vegetarian and non-vegetarian dietary intakes. The statistical procedures that the authors used identified five coherent diet classes:

Very high mix (25.5% of the sample)
High mix (21.4% of the sample)
Moderate mix (20.6% of the sample)
Low mix (about 16% of the sample)
Very low mix (about 16% of the sample).

The moderate to very high mix categories were predominantly non-vegetarian while the low and very low mix classes were vegetarian (e.g., 98% of the low mix category never include chicken, meat or fish).

Table 1 provides a graphic representation of the percent of each class that consumes different types of food on a daily basis. For instance, while 40 to 60% of women in the high mix group consumed milk or curd on a daily basis, 60 to 80% of the low mix group did so.

Table 1. Eating Specific Type of Food on a Daily Basis by Diet Group

Milk
	0%	1-20%	21-40%	41-60%	61-80%	81-100%
Very high
High
Moderate
Low
Very Low
Pulses or Beans
	0%	1-20%	21-40%	41-60%	61-80%	81-100%
Very high
High
Moderate
Low
Very Low
Green Leafy Vegetables
	0%	1-20%	21-40%	41-60%	61-80%	81-100%
Very high
High
Moderate
Low
Very Low
Other Vegetables
	0%	1-20%	21-40%	41-60%	61-80%	81-100%
Very high
High
Moderate
Low
Very Low
Fruits
	0%	1-20%	21-40%	41-60%	61-80%	81-100%
Very high
High
Moderate
Low
Very Low
Eggs
	0%	1-20%	21-40%	41-60%	61-80%	81-100%
Very high
High
Moderate
Low
Very Low
Chicken, Meat or Fish
	0%	1-20%	21-40%	41-60%	61-80%	81-100%
Very high
High
Moderate
Low
Very Low

While the diet patterns between the vegetarian classes (low and very low mix classes) and high and very high classes, the medium mix class mixed both vegetarian and non-vegetarian patterns. The authors say that the differences between the three non-vegetarian classes (moderate, high and very high) were trivial.

Food Intake Varies by Region

The authors examine how food intake patterns vary not only by class, but also by region. They analyze intake patterns of the above food types according to Indian states. They find significant differences by region. (See Table 1 in the article for detailed information on food intake by region.)

The proportion of the very low mixed-diet cluster was highest in the northern and central regions.
A very high mixed-diet pattern was seen mostly in the southern, western and north-eastern region. This pattern was observed least among those from the central region (18.3%).

What Factors Are Associated with Diet Patterns?

After identifying the five different diet classes, the authors then use a multinomial logistic regression procedure to identify other factors associated with the different diet classes.

The authors make the following general associations between diet class and social characteristics:

Affluence:

Women living in better conditions were almost equally as likely to be in either the very high or the low mixed-diet clusters than less affluent women.

Education:

Educated women were found more likely in the very high or low mixed-diet clusters than their counterparts.

Religion:

The very high or high mixed-diet pattern was characteristic of mostly Muslims and Christians compared other religions. The low mixed-diet cluster was mostly characteristic of other religious groups and the Hindus.

Ethnicity:

The very high and high mixed-diet patterns were lowest among scheduled tribe compared with scheduled caste and other backward caste women.

Work:

A very low or low mixed-diet pattern was observed predominantly among non-working women or those working in the agricultural sector. Women in the very high mixed-diet class were more likely to be in the professional and services sectors. Skilled or unskilled manual workers represented either the high or moderate mixed-diet cluster.

Table 2 provides a more detailed overview of the characteristics most associated with the different diet classes. (Note, the table only presents the most common characteristic within the diet class. The quantitative difference between the prevalence of one characteristic over another may be very small. Differences in prevalence of one characteristic versus another should not be interpreted as being statistically significant.)

Characteristics by Diet Group

	Very High	High	Medium	Low (primarily vegetarian)	Very low (primarily vegetarian
Spatial
Place of Residence
Urban
Rural
Region
North
Central
East
Northeast
West
South
*Socio-economic and Cultural*
Standard of Living
Low
Medium
High
Education
High school or more
Secondary
Primary
None
Religion
Others
Christian
Hindu
Muslim
Ethnicity
Scheduled caste
Scheduled tribe
Other backward caste
None
Type of Employment
Professional
Services
Agriculture
Skilled manual
Unskilled manual
Not working
*Interaction (Living Standard X Residence)*
High £ urban
Medium £ urban
Low £ urban
High £ rural
Medium £ rural
Low £ rural

Author Conclusion:

Indian women practice substantial heterogeneous dietary-mixing behaviors, dependent on complex interrelationships of demographic characteristics.

Funding Source:

University/Hospital:

University of Southhampton, Instituto Superior de Ciencias do Trabalho e da Empresa, Netherlands Interdisciplinary Demographic Institute, University of Groningen

Reviewer Comments:

Several limitations are noted:

Responses to survey reflect the immediate past and current dietary habits of the women
NFHS-2 survey did not specifically ask about cereal intake (rice and wheat consumption forms a major component of daily intake in India)
Survey is a cross-sectional representation. There is no information on quantity or quality of dietary intake over time.

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?	N/A
3.	Were study groups comparable?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.1.	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?	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	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.)	N/A
	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.)	N/A
	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%.)	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?	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.)	???
	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.)	???
	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?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		N/A
	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?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	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?		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?	N/A
10.	Is bias due to study's funding or sponsorship unlikely?		N/A
	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