Vegetarian Nutrition

VN: Therapeutic Vegetarian Diets and Attrition (2009)

Citation:

Delgado M, Gutiérrez A, Cano MD, Castillo MJ. Elimination of meat, fish and derived products from the Spanish-Mediterranean diet: effect on the plasma lipid profile. Ann Nutr Metab. 1996; 40 (4): 202-211.

PubMed ID: 8886248
 
Study Design:
Non-randomized trial.
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To investigate how the elimination of all animal products except eggs and milk products from a Mediterranean diet affects the plasma lipid profile in young, healthy subjects.

Inclusion Criteria:
  • Students or recent graduates in physical education
  • Consuming a Spanish-Mediterranean diet (similar to Mediterranean diet, except lower intake of pasta and higher intake of legumes)
  • Healthy subjects (devoid of metabolic or cardiovascular diseases)
  • Physically active.
Exclusion Criteria:

Subjects whose baseline eating pattern was based on fast food, and therefore, highly discordant from the traditional Spanish diet.

Description of Study Protocol:

Recruitment

Recruitment methodology was not reported in this research article.

Design

Fourteen subjects were evaluated twice: Before and two months after dietary manipulation. Evaluation consisted of detailed dietary assessment, anthropometric measurements, evaluation of aerobic capacity and analysis of the plasma lipid profile. The control subjects (six non-vegetarian and eight vegetarians) were matched for age, body weight, dietary habits and level of physical activity. The control subjects were also tested at a two-month interval. 

Blinding Used

No information was provided to the clinical laboratory concerning the characteristics and eating patterns of the subjects. 

Intervention

The subjects were given instructions to abstain from consuming all animal products except eggs and milk products for at least two months. Weekly personal interviews were held with all subjects throughout the study to assess and reinforce compliance.

Statistical Analysis

  • One-way analysis of variance (ANOVA) was used to evaluate overall group differences
  • When ANOVA test was significant, it was followed by the Newman-Keuls test to compare the individual groups
  • The student T-test for paired data was used to compare pairs of mean values
  • Linear regression analysis was used to estimate the association between variables.
Data Collection Summary:

Timing of Measurements

The  plasma lipid profiles were evaluated at baseline and two months later. The subjects were not studied at the same time, and the period of the study extended over two years.

Dependent Variables

All blood samples were drawn in the morning, after a fast of 12 to 15 hours.

  • Variable One: Plasma cholesterol measured by enzymatic methods adapted to a Technicon auto-analyzer
  • Variable Two: Triglyceride concentrations measured by enzymatic methods adapted to a Technicon auto-analyzer
  • Variable Three: Low and very low density lipoprotein (VLDL) determined by manganese and heparin precipitation
  • Variable Four: High density lipoprotein (HDL) cholesterol determined after low and very low density lipoproteins
  • Variable Five: Low density lipoprotein (LDL) cholesterol determined after low and very low density lipoproteins
  • Variable Six: Apolipoprotein A1 measured by immunonephelometry
  • Variable Seven: Apolipoprotein B measured by immunonephelometry.

Independent Variables

Spanish-Mediterranean diet, excluding all animal products except eggs and milk products.

Control Variables

  • Anthropometric measurements included weight, height, skin-fold thickness and circumferences of arm and leg
  • Body composition was determined by near infrared technology
  • Aerobic capacity was determined using  the Med-Graphics cardiopulmonary exercise system CPX.
Description of Actual Data Sample:
  • Initial N: 18
  • Attrition (final N): 14
  • Age: 20 to 25 years old
  • Ethnicity: Unknown
  • Other relevant demographics: Subjects, ten men and four women; controls, (non-vegetarians) four men and two women and (vegetarians) six men and two women
  • Location: Spain.
Summary of Results:

Dietary Patterns and Dietary Components

Table One
Daily intakes (mean±SEM) of several dietary components before and after the elimination of all meat and fish, but not eggs and dairy products, from a mixed Mediterranean diet in 14 healthy young subjects.

  Before After
Energy Intake, kcal
2,970±244
2,590± 254*
Protein, g
98.3±7.4 (13.2±0.5)
77.4±8.1*  (11.3±0.4)*
Carbohydrates, g
391±41 (49.6±2.3)
379±43 (55.2±1.6)*
Fat, g
118±9 (35.8±2.3)
93±9* (31.7±1.5)
  Saturated
43.8±5.0 (13.2±0.9)
34.8±4.5* (11.8±1.2)*
  Monosaturated
56.1±3.1 (17.2±2.3)
42.1±4.2* (14.6±1.0)*
  Polyunsaturated
17.2±2.3 (5.0±0.4)
15.2±2.8 (5.1±0.6)
 

Polyunsaturated/saturated ratio

0.40±0.03
0.44±0.05
  Cholesterol, g
0.47±0.06
0.28±0.03*
  Fiber, g
15±2
16±3

In parenthesis, the percentages of total energy intake
* Significant change (P< 0.05) after the second study period.

  • Baseline diet for the experimental group included meat and meat-derived products at an average rate of six to eight times per week; pig and chicken had a much greater predominance, and fatty fish, mostly prepared by frying, was eaten three to four times per week
  • At baseline, the experimental group presented a dietary pattern totally superposable to a non-vegetarian control population, but clearly different from that of vegetarian subjects
  • The experimental group decreased protein and fat consumption. However, the polyunsaturated/saturated fat ratio remained unchanged.
  • A significant decrease in cholesterol was observed
  • Carbohydrate and fiber remained unchanged. However, the percentage contribution of carbohydrate increased related to the decrease in the protein
  • No change in diet composition was observed in the vegetarian and non-vegetarian control group after the two-month interval
  • At the end of the study, the different dietary components did not differ between the experimental and the vegetarian control group, but differences now appeared between the experimental and non-vegetarian control groups, particularly in protein, fat and cholesterol intakes. 

Plasma Lipid Profiles

Experimental Subjects: Plasma lipid profile in 14 healthy young subjects before and two months after the elimination of all animal products (except eggs and dairy products) from a mixed Mediterranean diet.

 

Before (Mean ±SEM)

After (Mean ±SEM)
Total Cholesterol, mmol per L
4.53±0.13
4.29±0.13*
LDL Cholesterol, mmol per L
2.51±0.15
2.43±0.13
HDL Cholesterol, mmol per L
1.66±0.08
1.47±0.08*
LDL/HDL Cholesterol Ratio
1.57±0.11
1.69±0.12
Triglycerides, mmol per L
0.69±0.05
0.79±0.10
Apolipoprotein B, mg per dL
64±4
60±3
Apolipoprotein A¹, mg per dL
132±15
140±12
Apolipoprotein B/Apolipoprotein A¹ Ratio
0.52±0.04
0.46±0.04

*Significant change (P<0.05) after the second study period.

Control Subjects: Plasma lipid profile measured at a two-month interval, in six healthy young subjects regularly consuming a mixed Spanish-Mediterranean diet (non-vegetarian) and eight healthy young vegetarian subjects.

  Non-Vegetarian (Mean ±SEM) Vegetarian (Mean ± SEM)
Total Cholesterol, mmol per L
4.75±0.18
4.80±0.20
4.40±0.15 
4.36±0.15
LDL Cholesterol, mmol per L
2.84±0.13
2.83±0.13
2.62±0.05
2.61±0.05
HDL Cholesterol, mmol per L
1.59±0.06
1.63±0.07 
1.44±0.11
1.42±0.11
LDL/HDL Cholesterol Ratio
1.78±0.07
1.75±0.08
1.90±0.16
1.91±0.13
Triglycerides, mmol per L
0.73±0.06
0.74±0.14
0.76±0.04
0.74±0.04
Apolipoprotein B, mg per dL
65±4
62±4
58±4
54±3
Apolipoprotein A¹, mg per dL
135±8
133±6
137±6
134±6
Apolipoprotein B/Apolipoprotein A¹ Ratio
0.48±0.02
0.47±0.03
0.42±0.01
0.39±0.01

    Differences between both groups did not reach statistical significance.

  • At baseline there were no significant differences between the three groups (experimental and two control groups)
  • In the experimental group total plasma cholesterol levels significantly decreased, mainly because of the reduction of the HDL cholesterol fraction
  • No other statistical differences were found.

Other Findings

  • Although there was a significant reduction in total energy intake in the experimental group, body weight did not change during the study
  • The dietary manipulation had no negative effect on physical performance in the experimental group.
Author Conclusion:

The elimination of meat and fish but not eggs and milk products from the current Spanish-Mediterranean diet induced a slight but significant decrease in total plasma cholesterol concentrations in a group of healthy young persons. However, the decrease was mainly the result of the reduction in HDL cholesterol. This change in nutritional habits had no beneficial effects on the plasma lipid profile, at least in this study group.

Funding Source:
University/Hospital: University of Granada, Spain
Reviewer Comments:

This study of only 14 subjects has little strength to represent the population. The study's discrepancy regarding the subjects' decreased energy intake and lack of weight loss presents a concern of lack of variable control (free-living subjects) and preciseness in the study. As the authors noted, a two-month intervention period may not be sufficiently long enough to show meaningful plasma lipid profile changes.

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? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  3. Were study groups comparable? No
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  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? 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? 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
  3.5. 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? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? 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
  5.2. 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? 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? 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? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? No
  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? No
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? 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? No
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? No
  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? No
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  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? No
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  8.2. Were correct statistical tests used and assumptions of test not violated? No
  8.2. Were correct statistical tests used and assumptions of test not violated? No
  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)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
  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