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Vegetarian Nutrition

VN: Therapeutic Vegetarian Diets and Attrition (2009)

Citation:

Kestin, M, Rouse, IL, Correll, RA, Nestel, PJ. Cardiovascular disease risk factors in free-living men: Comparison of two prudent diets, one based on lactoovovegetarianism and the other allowing lean meat. Am J Clin Nutr. 1989; 50: 280-287.

PubMed ID: 2756914
 
Study Design:
Randomized controlled trial; incomplete block design
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To investigate whether partial substitution of meat protein for vegetable protein in a fat-modified, ovolactovegetarian diet would negate the overall cardiovascular risk-lowering effects, specifically blood pressure and serum lipids, of the LOV diet.

Inclusion Criteria:
  • Male
  • Participants at a non-profit fitness institute
  • Completion of a questionnaire and screening examination.
Exclusion Criteria:
  • Current treatment for:
    • Hyperlipidemia
    • Hypertension
    • Any condition likely to affect lipid metabolism or blood pressure
  • Cigarette smoking above one pack per day
  • Consumption of more than five standard alcoholic beverages per day
  • Jogging more than 20km per week.
Description of Study Protocol:

Recruitment

  • Subjects were recruited from a non-profit fitness institute in Australia, however no further description of recruitment procedures was provided
  • 30 men were recruited; 26 men completed the study.

Design

RCT; incomplete block design

  • Baseline values measured on habitual diet
  • Participants randomly assigned to complete two of three dietary treatments (AUS, LOV or LM)
  • Each diet was of six-week duration
  • Six combinations of treatments.

Experimental Design

Diet Order First Diet Second Diet
1 AUS LOV
2 LOV AUS
3 AUS LM
4 LM AUS
5 LOV LM
6 LM LOV

AUS=high-fat, typical Australian diet
LOV=low-fat, ovolactovegetarian diet
LM=LOV diet with 60% of plant protein replaced with lean meat.

Blinding Used

NA.

Intervention

Dietary Intervention Using Three Diets

  • Each intervention was of six-week duration
  • All diets met or exceeded the Australian Recommended Dietary Intakes for vitamins and minerals
  • Diets designed using a computer database of foods
    • Nutrient composition based on McCance and Widdowson's The Composition of Foods,4th ed., 1978
    • Modified to include Australian foods from published sources, commercial sources and direct food analysis.

Diets

  • Australian high-fat diet (AUS): Nutrient content similar to diet consumed by Australian men, as found in the 1983 National Dietary Survey.
  • Fat-modified diets, based on recommendations of the National Heart Foundation of Australia for macronutrients and type of fat for the general public. Diets matched for: Energy, protein, amount and type of fat, amount of carbohydrate (including amount and type of non-starch polysaccharide), cholesterol, sodium, potassium, calcium, magnesium.
    • Two specific diets
      • Ovolactovegetarian diet (LOV): Used meat substitutes including soy and peanut protein, but mainly based on wheat gluten
      • Lean meat (LM)
        • Substituted at 60% of plant protein in LOV with lean meat
        • Provided daily average of 250g lean meat
        • Processed meat: Ham, corned beef, chicken sausage
        • Fresh meat: Lean beef, chicken.
  • Seven-day cycle menus
    • Designed at four energy levels: 2,100kcal, 2,400kcal, 2,700kcal and 3,000kcal per day
    • Discretionary allowance of 300kcal per day derived from low-fat foods (mainly beverages).

Energy Requirements of Participants

  • Estimated by use of predictive equations
  • Adjusted for physical activity (determined by interview)
  • Participants assigned to one of the four menu plans (see above)
  • Energy levels changed as needed, according to weight changes and mainly during basal period.

Foods Used in Study

  • Pre-weighed and portion packed
  • Major sources of protein and fat were provided by:
    • Kraft Foods Ltd.
    • Kelloggs (Aust) Pty Ltd.
    • Dandy Meats (Aust) Ltd.
    • Sanitarium Health Food Co.
    • Safcol Holdings Ltd.
    • Meadow-Lea Foods
    • EOI Pty Ltd.
    • Ballard Agencies Pty Ltd.
  • Participants purchased bread, milk, fruit and vegetables.

Participants were provided with menus, cooking instructions and sets of measuring cups and spoons.

Food Diaries

  • Four-day measured food records
    • At baseline on their habitual diet
    • During each dietary intervention
    • Note any deviations from usual pattern (e.g., eating out, illness, etc.).

Participants maintained baseline exercise patterns throughout the study.

Measurements

  • Diets
    • Food diaries: Four-day measured food records
      • At baseline on their habitual diet
      • During each dietary intervention
      • Note any deviations from usual pattern (e.g., eating out, illness, etc.).
  • Blood pressure: Measured at each visit (every two weeks) by a single observer
    • Right arm
    • After five minutes' rest
    • Sitting position
    • Automated sphygmomanometer used
    • Three readings one minute apart, averaged for analysis.
  • Heart rate: Measured at each visit by a single observer
    • Right arm
    • After five minutes' rest
    • Sitting position.
  • Serum lipids and lipoproteins
    • 12-hour fasting blood sample
    • Participants asked not to drink alcohol for 24 hours before each visit
    • Blood sample collected at baseline and at each visit
    • Serum total, LDL and HDL cholesterol and triglyceride concentrations were measured.
  • Urine sample
    • Overnight 12-hour sample
    • Collected at baseline and at the end of each six-week diet intervention
    • Measurement of sodium, potasium and creatinine excretion.
  • Body weight: Measurement frequency not specified
  • Food analysis
    • Directly analyzed samples of AUS, LOV & LM diets based on 2400 calorie/day menu
    • Procedure for protein analysis
      • Each day's food sample homogenized
      • Seven-day weighted representative sample prepared
      • Lyophilized
      • Ground in a liquid nitrogen grinder
      • Stored at -18°C for analysis of N
      • Calculation of protein in sample as Nx6.25.
    • Procedure for fat analysis: Total lipid extracted fatty acid composition determined by standard AOAC methods.

Statistical Analysis

  • Results expressed as weighted means, obtained from within- and between-person analysis
  • Multiple regression, with subject effects removed as covariates
  • Statistical significance, P<0.05.
Data Collection Summary:

Timing of Measurements

  • Dietary intervention
    • Initial assessment of habitual diet
    • Each diet was followed for six weeks.
  • Diet records: Completed for a four-day period at baseline and during each dietary intervention
  • Blood pressure and heart rate: Measured at each visit
  • Serum lipids and lipoproteins: Blood collected and assessed at each visit
  • Urine collection: At baseline and at the end of each six-week intervention
  • Body weight: Measurement frequency not specified.

Dependent Variables

  • Primary variables
    • Serum lipids (total, LDL and HDL cholesterol and triglyceride concentrations), measured in mmol per L
    • Blood pressure measured in mmHg.
  • Other variables measured
    • Body weight
    • Urinary sodium, potassium and creatinine excretion.

Independent Variables

Two low-fat prudent diets; an ovolactovegetarian diet (LOV) and a lean-meat diet (LM) that replaced approximately 60% of the plant protein in the LOV diet with lean meat.

Control Variables

  • Dietary protein and fat sources were provided to the participants
  • Seven-day cycle menus were used during the intervention periods.
Description of Actual Data Sample:
  • Initial N: 30 males
  • Attrition (final N): 26 males
  • Age: 28 to 64 years
  • Ethnicity: Not specified
  • Other relevant demographics: Australian residents.

Anthropometrics

Baseline Characteristics

  x±SD Range
Age (years) 44±10 28-64
BMI (kg per m2) 25.5±3.2 19.9-28.9
Serum Total Cholesterol (mmol per L) 6.10±1.08 4.7-9.1
Systolic BP (mmHg) 127±11 119-151
Diastolic BP (mmHg) 78±10 62-92

Location

Australia.

Summary of Results:

Major Findings

  • Substitution of 60% of plant protein in the LOV diet with lean meat protein did not negate the lowering of serum total and LDL cholesterol and systolic blood pressure
  • Weight loss
    • Small but significant weight loss for participants on LOV
    • Body weight change did not affect significance of changes in serum lipids or blood pressure.
  • Serum lipids
    • Serum total and LDL cholesterol were lowered by both LOV and LM diets, but LOV was significantly more effective
    • Progressive reduction in serum total, LDL and HDL cholesterol from AUS to LM to LOV urinary excretion
    • Total cholesterol fell by 5% and 10% for LM and LOV, respectively
    • LDL decreased by 7% and 9% for LM and LOV, respectively
    • Serum triglycerides increased on both LOV (23%) and LM (24%) diets.
  • Blood pressure: Both LOV and LM diets significantly lowered systolic blood pressure, compared to AUS, even after accounting for weight loss
  • Urinary excretion
    • 12-hour urinary sodium excretion was significantly less on LOV than AUS or LM
    • Creatinine excretion lower on LOV (due to minimal creatinine intake from diet free of muscle protein). 

Variables1

Baseline
(N=26)

AUS
(N=17)

LOV
(N=17)

LM
(N=18)

P-Value

Total Cholesterol (mmol/L) 6.07 6.04*¶  5.43¥ 5.76

*P<0.01, AUS vs. LM
¶P<0.001, AUS vs. LOV
¥P<0.01, LOV vs. LM

LDL (mmol/L) 4.08 4.01*¶ 3.40¥ 3.74

*P<0.01, AUS vs. LM
¶P<0.001,AUS vs. LOV
¥P<0.01, LOV vs. LM

HDL (mmol/L) 1.46 1.45§ 1.36 1.32 §P<0.05, AUS vs. LM
Triglycerides (mmol/L) 1.28 1.15*Þ 1.41 1.43 ÞP<0.01, AUS vs. LOV
Systolic BP (mmHg) 128 126§Þ 122 123

§P<0.05, AUS vs. LM
ÞP<0.01, AUS vs. LOV

Adjusted Systolic BP (mmHg)2   126§+ 123 123

§P<0.05, AUS vs. LM
+P<0.05, AUS vs. LOV

Diastolic BP (mmHg) 79.0 77.1 75.5 76.1  
Adjusted Diastolic BP (mmHg)2   76.9 76.1 75.7  
Weight (kg) 80.5 79.7Þ 79.0¥ 79.8

ÞP<0.01, AUS vs. LOV
¥P<0.01, LOV vs. LM

Urinary Sodium (mmol/12h) 72.8 78.2Þ 62.8¥ 73.6

ÞP<0.01, AUS vs. LOV
¥P<0.01, LOV vs. LM

Urinary Potassium (mmol/12h) 39.0 28.3  27.7 30.7  
Sodium:Potassium 2.7 2.8 2.4 2.4  
Urinary Creatinine (mmol/12h) 8.8 8.7¶ 6.5# 8.5

¶ P<0.001, AUS vs. LOV
#P<0.001, LOV vs. LM

  1. Reported values are weighted means
  2. Systolic and diastolic blood pressures adjusted for weight change.

Other Findings

  • Inclusion of lean meat (LM) led to serum cholesterol levels intermediate between AUS and LOV diets
  • LOV and LM diets were closely matched in all nutrients except type of protein and both LOV and LM differed from AUS in nutrients that may affect serum lipids, e.g., total fat, saturated fatty acids, fiber, potassium, calcium and magnesium
  • The main protein source in the LOV diet, wheat gluten, increased glutamate intake, which may have a hypocholesterolemia effect
  • Serum triglyceride concentration increased with LOV and LM
  • HDL was reduced by LM diet
  • Participants expressed a clear preference for LM over both LOV and AUS.
Author Conclusion:

Partial substitution of lean meat for plant protein in a low-fat diet does not negate the overall cardiovascular risk lowering of the ovolactovegetarian diet and may make following a prudent diet more widely acceptable by the general population.

Funding Source:
Industry:
Kraft Foods, Kellogg, Dandy Meats Ltd, Sanitarium Health Foods Co.
Food Company:
Not-for-profit
National Heart Foundation of Australia
Other non-profit:
Other: Australian Meat and Livestock Co.
In-Kind support reported by Industry: Yes
Reviewer Comments:
  • Because many Western countries follow a meat-based eating pattern, the authors are attempting to find a more "acceptable" way for the general population to follow a vegetarian diet, in order to impact the burden of cardiovascular disease in the West
  • This study was supported by the National Heart Foundation of Australia
  • The meat industry was well-represented in the list of companies donating foods for this study
  • The Australian Meat and Livestock Corporation funded the purchase of meat for this study.
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? 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? 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? No
  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? No
  2.3. Were health, demographics, and other characteristics of subjects described? No
  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) 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? 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? No
  4.4. Were reasons for withdrawals similar across groups? No
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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? Yes
  5.5. In diagnostic study, were test results blinded to patient history and other test results? Yes
  6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? No
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? No
  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? No
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  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? 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? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
  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? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? ???
  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? No
10. Is bias due to study's funding or sponsorship unlikely? No
  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? No
  10.2. Was the study free from apparent conflict of interest? No