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Vegetarian Nutrition

VN: Therapeutic Vegetarian Diets and Attrition (2009)

Citation:
Daubenmier JJ, Weidner G, Sumner MD, Mendell N, Merritt-Worden T, Studley J, Ornish D. The contribution of changes in diet, exercise, and stress management to changes in coronary risk in women and men in the multisite cardiac lifestyle intervention program. Ann Behav Med. 2007 Feb; 33 (1): 57-68.
PubMed ID: 17291171
 
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:

Evaluate or examine the relative contribution (i.e., additive and interactive effects) of dietary fat reduction, increased exercise and increased stress management practice to changes in coronary and psychosocial risk factors in 293 females and 576 males with coronary heart disease (CHD) participating in the Multisite Cardiac Lifestyle Intervention Program (MCLIP) over a three-month period.

Inclusion Criteria:

Patients were included if they were diagnosed with CHD by a physician or health plan, which was defined as one of the following:

  • Ischemia documented with non-invasive testing such as exercise testing, nuclear imaging, echocardiogram or other test clearly demonstrating ischemia
  • Cardiac catheterization demonstrating CHD
  • A history of percutaneous coronary intervention (PCI), coronary artery bypass surgery (CABG) or myocardial infarction (MI
  • Eligibility for PCI or CABG.
Exclusion Criteria:

Exclusion criteria included:

  • Ischemic left main CHD with obstruction greater than 50%
  • Significant (more than 70%) proximal left anterior descending artery and proximal left circumflex artery disease and an ejection fraction less than 50%
  • Unstable angina
  • Hypotensive response to exercise (more than 20mm Hg drop in systolic BP)
  • History of exercise-induced ventricular tachycardia or third degree heart block without evidence of current stability
  • CABG or MI within four weeks, unless approved by medical director
  • Congestive heart failure with functional limitation and unresponsiveness to medications
  • Current tobacco user not concurrently enrolled in a smoking cessation program with a two-month history of smoking cessation
  • Uncontrolled malignant ventricular arrhythmia despite medications or implantable cardiac defibrillator, unless approved by medical director
  • Primary residence more than one hour of commute from the program site, unless approved
  • History of substance abuse disorder without documentation of minimum one-year stability
  • Impaired cognitive function such as dementia or delirium
  • English language illiteracy unless program site could accommodate
  • Non-ambulatory
  • Uncooperative spouse or partner, defined as obstructive in attitude or behavior
  • Likely to be disruptive to group setting. 
Description of Study Protocol:

Recruitment

  • Participants were enrolled in the MCLIP program in four states and were referred to the program by their physicians or self-referred through advertising or media publicity
  • All participants received approval from their physician to enroll
  • Participants completed informed consent and medical release forms. 

Design

Non-randomized trial (intervention). 

Intervention

Lifestyle change program that included onsite lectures, demonstrations (cooking), one-hour supervised exercise, one hour of stress management, a meal consistent with guidelines and one hour of support group.

Dietary guidelines consisted of a very low-fat, plant-based, whole foods diet, high in complex carbohydrates, low in simple carbohydrates, which included fruits, vegetables, grains, legumes, one cup of nonfat dairy and egg whites.

  • Sodium was restricted for patients with hypertension (HTN), congestive heart failure or renal disease
  • Participants were instructed to eat one serving of a soy product each day
  • Diet composition included:
    • 10% daily kcal from fat
    • 15% from protein
    • 75% from complex carbohydrates.
  • Total calories were unrestricted, unless the participants was overweight and not losing weight
  • A low-dose multivitamin and three grams of fish oil per day were recommended.

Exercise prescription included aerobic exercise a minimum of three hours per week and 30 minutes per session exercising within their prescribed heart rate (45% to 80%) or perceived exertion levels. Participants were also asked to perform strength-training activities a minimum of two times each week.

Statistical Analysis

  • Independent sample T-tests for continuous variables, chi-squared analyses for categorical or dichotomous variables
  • ANOVA for repeated measures tested sex, time and their interaction on health behaviors, coronary risk factors and psychosocial factors
  • Hierarchical multiple regression analyses were conducted to examine additive and interactive effects of changes in diet, exercise and stress management (three health behaviors) as well as sex on changes in coronary risk factors and psychosocial factors.
Data Collection Summary:

Timing of Measurements

  • Measurements for anthropometrics, blood pressure, plasma and dietary adherence assessments were taken at baseline and at three-month follow-up
  • Timing of measurements for exercise and psychosocial variables were not reported
  • Medications were documented at baseline.

Dependent Variables

  • Weight and height were measured without shoes and removal of excess clothing; measurements were obtained from the same calibrated scale (types and to the nearest decimal endpoint were not reported) 
  • Blood pressure was measured by a trained health professional using a calibrated sphygmomanometer according to the American Heart Association's guidelines
  • Total cholesterol, HDL-C, and TG were measured and LDL-C was either measured or calculated depending on the site. Descriptions of the techniques or equipment used were not provided.
  • Hemoglobin A1c was also measured (techniques not reported)
  • Depression symptoms were measured using the Center for Epidemiological Scale-Depression (CES-D) and scores of zero to 60 were applied
  • Hostility was measured using the Cook-Medley Hostility Scale, a 27-item measure containing three subscales: cynicism, hostile effect and aggressive responding; total scores range from zero to 27
  • Perceived stress was assessed by a 10-item Perceived Stress Scale; participants' responses ranged from zero (never) to four (very often) and total scores ranged from zero to 40.

Independent Variables

  • Diet
  • Exercise and education (lectures)
  • Group support
  • Stress management.
Description of Actual Data Sample:

 

Initial N

869 non-smoking CHD patients (293 females, 576 males).

Attrition (Final N)

  • 18 women and 22 men did not complete the thee-month follow-up (4.5%)
  • Final N=829.

Age

Mean age: 59±8.9 years for males, 60±9.4 years for females.

Ethnicity:

  • 94.2% white males, 95.1% white females
  • No other ethnic background was reported.

Other Relevant Demographics

  • Marital status: 88.9% males and 63.8% females were married
  • Employment: 58.4 % males and 47.5% females were employed
  • Education: 52.8% males and 32.2% females had college degrees (some sites did not collect this information so data was reported for 90% of overall males and 96% of overall females)
  • Medical history: BP, lipid profile
  • Medications: Lipid lowering, beta blockers, ACE inhibitors, anticoagulants and nitrates
  • Exercise capacity measured as MET
  • Psychosocial factors.

Anthropometrics

Weight, height and BMI calculated. 

Location:

West Virginia, Pennsylvania, Illinois and Nebraska, insurance agencies.

 

Summary of Results:

Variables
Baseline (Males)
Three-month
Baseline (Females)
Three-month
Statistical Significance
Blood Lipids
Total cholesterol (mg per dL)
167±38
143±34
193±46
172±42
P=0.001, time and sex
P=0.24, time x sex
HDL (mg per dL) 
39±10
35±9
49±13
43±11
P=0.001, time and sex
P=0.003, time x sex
HDL:LDL-C
4.5±1.5
4.3±1.3
4.1±1.4
4.1±1.2
P=0.01, sex; 0.001, time and times x sex
LDL (mg per dL)
94±32
78±29
107±36
92±34
P=0.001, time and sex
P=0.47, time x sex
Triacylglycerol (mg per dL)
175±108
156±77
185±113
183±104
P=0.005, sex and 0.001, time P=0.007, time x sex
Body Composition
Weight (kg)
95.9±18.2
90.4±16.4
83.2±19.8
79.1±18.5
P=0.001, sex, time and time x sex
Diabetes Related Variables
A1c (%)
7.2±1.5
6.4±1.0
8.0±1.7
7.1±1.1
P=0.001, sex and time; 0.51, time x sex
Blood Pressure
Systolic
132±18
120±15
131±18
122±16
P=0.70, sex; 0.001, time; 0.01, time x sex
Diastolic
78±10
71±9
76±10
71±9
P=0.09, sex; 0.001, time; 0.20, time x sex
Health Behaviors
Dietary fat (percent kcal)
24±11.6
8.9±2.5
25.5±10.9
9.6±3.3
P=0.03, sex; 0.001, time; 0.43, time x sex
Exercise (hours per week)
2.0±2.2
3.9±1.7
1.2±1.5
3.5±1.3
P=0.001, sex & time; 0.08, time x sex
Stress management (hours per week)
0.3±1.1
6.0±2.2
0.5±1.3
6.3±2.0
P=0.029, sex; 0.001, time; 0.46, time x sex
Psychosocial Factors
Depression (CES-D)
11.4±8.8
7.2±6.8
13.5±9.6
7.3±6.8
P=0.04, sex; 0.001, time and time x sex
Hostility
9.0±4.9
7.4±4.5
7.0±4.4
6.1±4.3
P=0.001, sex and time; 0.019, sex x time
Perceived stress
14.3±7.1
10.1±5.8
16.2±8.0
10.5±6.4
P=0.14, sex; 0.001, time; 0.002, sex x time
 

Other Findings

  • Multiple regression analyses showed that three-month improvements in stress management, exercise and dietary fat intake were significantly associated with three-month improvements in coronary risk and psychosocial factors
  • Changes in weight indicated that improved stress management and dietary fat intake were additively related to weight loss (P<0.01 and 0.001 respectively)
  • Decreased total cholesterol was predicted by reduced dietary fat intake (P<0.001) and a sex-times-exercise interaction (P<0.10), indicating that increased exercise was significantly related to lower total cholesterol in women (P<0.05) but not men (P=0.27)
  • Reduced dietary fat was the only predictor related to improvement in LDL-C (P<0.001)
  • Increased stress management was related to a decrease in TG (P<0.05) 
  • For patients with diabetes, increased stress management was related to reductions in hemoglobin A1c (P<0.05)
  • Changes in health behaviors did not predict improvements in systolic or diastolic blood pressure
  • Exercise-times-dietary fat interaction revealed that those who showed the greatest improvements in exercise and dietary fat reported greatest improvement in perceived stress (P<0.01).
Author Conclusion:
  • Results highlight the value of modifying multiple health behaviors to reduce coronary risk factors and enhance psychosocial functioning in patients with CHD 
  • Improvements in dietary fat intake, exercise and stress management were individually, additively and interactively related to coronary risk and psychosocial factors
  • Limitation of the study is its reliance on self-reported measures of health behaviors. Participants may have inflated their adherence for social reasons.
  • If objective measures of health behaviors were employed in the study, stronger relations between changes in health behaviors and coronary risk and psychosocial factors may have been detected
  • Authors' second limitation is that they cannot conclude that improvements in health behaviors are directly responsible for observed improvements in coronary risks and psychosocial factors.
Funding Source:
Government: Department of the Army; Department of Health and Human Services
Industry:
Reviewer Comments:

Strengths of the Study

  • Large numbers of participants with reasonable numbers of men and women; sample was from four states, which would have been excellent for generalization
  • Utilized a variety of variables that can affect lifestyle and a number of outcomes.

Weaknesses

  • The dietary aspect of the study was poorly managed; apart from the composition of the diet placed in the hands of the participants, calories were unrestricted so it was difficult to determine the outcome of weight or lipid profile due to the "very low-fat, plant-based diet," which is important to us in this review
  • In the report, energy and macronutrient intake were not the focus of this paper. Even though the authors indicated that three-day food diaries were part of the study, no results were provided.
  • Adherence to the diet was not reported, so it was difficult to determine the effect it could have on weight or lipid profiles
  • BMI was mentioned but only the baseline data was reported; no mention of BMI after three months of intervention. 

Overall good study; however, it did not address the issues in vegetarian nutrition and its impact on weight, BMI, lipid profiles or diabetes.

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) N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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? No
5. Was blinding used to prevent introduction of bias? No
  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.) 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.) No
  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? 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? 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? No
  6.6. Were extra or unplanned treatments described? No
  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? No
  7.2. Were nutrition measures appropriate to question and outcomes of concern? No
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  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? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  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)? 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)? Yes
  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? Yes
  10.2. Was the study free from apparent conflict of interest? Yes