VN: Therapeutic Vegetarian Diets and Attrition (2009)
Barnard, ND, Scialli, AR et al. Effectiveness of a low-fat vegetarian diet in altering serum lipids in healthy premenopausal women. Am J of Cardiology. 2000 (Apr); 85: 969-972.
PubMed ID: 10760336

To investigate whether following a low-fat vegetarian diet would lower total and LDL cholesterol concentrations in healthy pre-menopausal women.
- Pre-menopausal females
- At least 18 years old
- Exhibiting moderate to severe pain accompanying menstrual periods
- Already participating in a study examining the effect of a low-fat vegetarian diet on serum sex-hormone-binding globulin concentration and dysmenorrhea.
- Irregular menstrual cycles
- Menstrual cycles of either less than 25 days or more than 35 days
- Physical illness affecting eating behavior or causing pain
- History of hormone-related illness, e.g., diabetes or thyroid disease
- History of mental illness
- Alcohol or drug abuse
- Use of oral contraceptives in previous six months
- Use of drugs known to affect hormonal function in previous six months
- Structural abnormality that could account for abdominal pain.
Recruitment
- Newspaper advertisements
- Notices mailed to gynecologists
- Washington, DC area
- No monetary compensation provided.
Design RCT Crossover Design
- Randomization done by computer-generated random number list
- Two groups (N=24, N=27)
- Received the same treatments, but in opposite order
- Initial baseline period lasting one full menstrual cycle; no dietary changes
- Two successive replications, each lasting two full menstrual cycles
- Diet intervention phase using a low-fat vegetarian diet
- Placebo "supplement" phase.
Special Diet Prescriptions or Modifications
Nutrients | Intervention (Vegetarian or Vegan) | Usual Diet with Placebo Supplement |
Energy | None | None |
Protein | None | None |
Carbohydrates | None | None |
Fat/fatty acids | Approximately 10% | None |
Other |
Grains, vegetables, legumes and fruits. Avoid |
None |
Supplements | B12 (2 micrograms) | None |
Length of Treatment
Two menstrual cycles (approximately eight weeks).
Follow-Up
None reported.
Behavioral Interventions
Weekly one-hour nutrition training and support meetings throughout study duration
- Cooking demonstrations
- Lectures
- Grocery samples of vegetarian foods occasionally provided during diet intervention phase
- Spouses or partners of subjects were invited.
Blinding Used
Subjects blinded to the nature of the supplement (B12 or placebo).
Intervention
- Dietary intervention consisting of a low-fat (under 10% calories from fat) vegetarian diet
- Foods allowed:
- Grains
- Vegetables
- Legumes
- Fruits.
- Foods not allowed:
- Animal products
- Added oils
- Fried foods
- Avocados
- Olives
- Nuts
- Nut butters
- Seeds.
- Foods allowed:
Statistical Analysis
- Within-subjects analyses of variance to assess effect of the intervention diet
- For each variable, analyses were conducted on the change scores obtained from:
- Difference between baseline and intervention diet phase
- Difference between baseline and supplement phase.
- Significant difference indicated that change from baseline to intervention was different from change from baseline to supplement
- Results reported as means±SD
- Significance: P<0.05
- Order effects of interventions tested also; method not described.
Timing of Measurements
- Interventions
- Initial baseline period with no dietary changes, lasting one full menstrual cycle
- Two intervention phases, each lasting two full menstrual cycles.
- Three-day dietary record
- Two weekdays and one weekend day
- Recorded by subject between Days Six and 14 of menstrual cycle.
- Body weight measured
- Measured on a single occasion
- Between Days 14 and 21 of menstrual cycle
- In street clothes
- Measured to nearest 0.2kg
- Same scale used during each study phase.
- Blood sample collection
- On Day Six of each participant's menstrual cycle
- Serum separated and frozen
- Laboratory determinations for all participants during each replication were run in the same batch at the end of the study.
Dependent Variables
- Serum lipids (total cholesterol, LDL, HDL), measured in mg per dL, were the primary dependent variables
- The researchers also measured changes in body weight and BMI.
Independent Variables
Low-fat vegetarian diet with approximately 10% of calories derived from fat.
- Initial N: 51 pre-menopausal females
- Attrition (final N): 31.
Reasons for Non-Completion
- Onset of menopause: One
- Pregnancy: One
- Repeatedly missing meetings: Two
- Non-compliance with intervention diet: Two
- Extended travel or scheduling difficulties: Two
- Death in the family: One
- Major financial problems: One
- Spouse objections to diet: One
- Unknown reason: One
- Exclusion from data analysis for not returning all data forms: Four.
Age
22 to 48 years old (mean, 36.1).
Ethnicity
- White, non-Hispanic: 21
- Black, non-Hispanic: Nine
- White, Hispanic: Four
- Black, Hispanic: Zero
- Asian: One.
Other Relevant Demographics
- Single: 24
- Married: Eight
- Separated, divorced, widowed: Three
- Mean age of menarche: 12.3 years
- Pregnancies (median, range): Zero, zero to 13
- Live births (median, range): Zero, zero to two
- Living children (median, range): Zero, zero to two.
Anthropometrics
No significant differences on important measures.
Location
Washington, DC area.
Summary
- Total and LDL cholesterol decreased by 13.2% and 16.9%, respectively, from baseline to intervention (P<0.001)
- Changes in cholesterol were not associated with baseline BMI or change in BMI
- HDL decreased 16.5%
- LDL-to-HDL ratio remained unchanged
- Mean serum triacylglycerol concentration increased 18.7% (P<0.001) from baseline to intervention, but remained under one
- One mmol per L throughout the study.
- Intake of other nutrients during intervention diet phase:
- Calcium intake decreased (P<0.001)
- Sodium intake decreased (NS)
- Protein intake decreased (P<0.01)
- Due to decreased sodium and protein intake, renal losses were reduced, favoring improved calcium balance.
Intake Results
Nutrient |
Baseline or Prescribed |
Usual Diet with Placebo (Actual Intake) |
Vegan/Vegetarian (Actual Intake) |
|
Nutrients |
Energy (mJ or kcal) |
7.9 (1.8) |
7.3 (2.0) |
6.4 (1.6)* |
Protein (g) |
67 (20) |
60 (17) |
43 (11)+ |
|
Carbohydrates (g) |
295 (76) |
283 (91) |
311 (89) |
|
Total Sugar (g) |
110 (42) |
101 (45) |
109 (38)+ |
|
Total Fiber (g) |
26 (9) |
23 (11) |
31 (9) |
|
Fat (g) |
52 (24) |
43 (23) |
17 (10)+ |
|
Saturated Fat (g) |
15(12) |
12 (10) |
3 (3)+ |
|
Polyunsaturated Fat (g) |
9 (6) |
9 (5) |
4 (3)+ |
|
Cholesterol (mg) |
132 (137) |
132 (91) |
6 (8)+ |
|
Micronutrients |
Sodium (mg) |
2,640 (880) |
2,400 (790) |
2,170 (770) |
Calcium (mg) |
750 (331) |
658 (283) |
466 (199) |
|
Pyridoxine (mg) |
2.5 (3.1) |
2.5 (2.5) |
4.9 (16.9)+ |
|
Foods |
Caffeine |
97 (107) |
82 (104) |
57 (70) |
Outcomes
Variables |
Baseline |
Usual Diet with Placebo Supplement |
Low-Fat Vegetarian Diet with B12 Supplement |
Statistical Significance of Difference Between Baseline and Vegetarian Diet |
Total Cholesterol (mg/dL) |
163±30 |
162±36 |
141±36 |
P<0.001 |
HDL (mg/dL) |
49±11 |
52±15 |
41±13 |
P<0.001 |
LDL (mg/dL) |
97±24 |
94±29 |
80±26 |
P<0.001 |
VLDL (mg/dL) |
16±7.3 |
16±7.5 |
19±10.4 |
P<0.001 |
Triacylglycerol (mg/dL) |
81±36 |
81±38 |
97±52 |
P<0.01 |
LDL/HDL |
2.0±0.7 |
1.9±0.8 |
2.0±0.7 |
NS |
Weight (kg) |
69.4±12.9 |
68.5±13.0 |
66.9±12.5 |
P<0.001 |
BMI (kg/m2) |
25.5 ± 5.2 |
25.2±5.2 |
24.6±4.9 |
P<0.001 |
Other Findings
- Order of diet presentation influenced results: Weight lost during low-fat vegetarian diet phase not fully regained during subsequent usual diet plus placebo phase
- Weight change during diet phase was associated with changes in energy intake
- Significant correlation between initial BMI and subsequent weight loss during the diet intervention.
Initial BMI (kg/m2) |
Weight Loss (kg) |
Less than 22.0 | 1.4 |
22.0 to 26.5 | 3.3 |
More than 26.5 | 2.9 |
Following a low-fat vegetarian diet results in significant reductions in serum total and LDL concentrations and significant weight-loss in the short term (within six months) in healthy, free-living pre-menopausal women.
Government: | NIDDK |
- This is a study within a larger study investigating the effect of a low-fat vegetarian diet on serum sex-hormone-binding globulin concentration and dysmenorrhea
- The investigators reported limitations:
- Study did not address long-term clinical effects of diet
- Diet may not be sustainable long-term
- Food consumption may have been under-reported
- Participants' symptomatology may have increased their motivation
- Participants may have been knowledgeable about nutrition.
Quality Criteria Checklist: Primary Research
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Relevance Questions | |||
1. | Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) | Yes | |
1. | Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) | Yes | |
2. | Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? | Yes | |
2. | Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? | Yes | |
3. | Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? | Yes | |
3. | Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? | Yes | |
4. | Is the intervention or procedure feasible? (NA for some epidemiological studies) | Yes | |
4. | Is the intervention or procedure feasible? (NA for some epidemiological studies) | Yes | |
Validity Questions | |||
1. | Was the research question clearly stated? | Yes | |
1. | Was the research question clearly stated? | Yes | |
1.1. | Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? | Yes | |
1.1. | Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? | Yes | |
1.2. | Was (were) the outcome(s) [dependent variable(s)] clearly indicated? | Yes | |
1.2. | Was (were) the outcome(s) [dependent variable(s)] clearly indicated? | Yes | |
1.3. | Were the target population and setting specified? | Yes | |
1.3. | Were the target population and setting specified? | Yes | |
2. | Was the selection of study subjects/patients free from bias? | Yes | |
2. | Was the selection of study subjects/patients free from bias? | Yes | |
2.1. | Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? | Yes | |
2.1. | Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? | Yes | |
2.2. | Were criteria applied equally to all study groups? | Yes | |
2.2. | Were criteria applied equally to all study groups? | Yes | |
2.3. | Were health, demographics, and other characteristics of subjects described? | Yes | |
2.3. | Were health, demographics, and other characteristics of subjects described? | Yes | |
2.4. | Were the subjects/patients a representative sample of the relevant population? | Yes | |
2.4. | Were the subjects/patients a representative sample of the relevant population? | Yes | |
3. | Were study groups comparable? | Yes | |
3. | Were study groups comparable? | Yes | |
3.1. | Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) | Yes | |
3.1. | Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) | Yes | |
3.2. | Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? | Yes | |
3.2. | Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? | Yes | |
3.3. | Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) | Yes | |
3.3. | Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) | Yes | |
3.4. | If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? | 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")? | Yes | |
3.6. | If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? | Yes | |
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%.) | No | |
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%.) | No | |
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? | ??? | |
4.4. | Were reasons for withdrawals similar across groups? | ??? | |
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? | 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? | 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? | Yes | |
6.5. | Were co-interventions (e.g., ancillary treatments, other therapies) described? | Yes | |
6.6. | Were extra or unplanned treatments described? | Yes | |
6.6. | Were extra or unplanned treatments described? | Yes | |
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? | 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? | 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? | ??? | |
8.2. | Were correct statistical tests used and assumptions of test not violated? | ??? | |
8.3. | Were statistics reported with levels of significance and/or confidence intervals? | Yes | |
8.3. | Were statistics reported with levels of significance and/or confidence intervals? | Yes | |
8.4. | Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? | No | |
8.4. | Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? | No | |
8.5. | Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? | Yes | |
8.5. | Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? | Yes | |
8.6. | Was clinical significance as well as statistical significance reported? | Yes | |
8.6. | Was clinical significance as well as statistical significance reported? | Yes | |
8.7. | If negative findings, was a power calculation reported to address type 2 error? | N/A | |
8.7. | If negative findings, was a power calculation reported to address type 2 error? | N/A | |
9. | Are conclusions supported by results with biases and limitations taken into consideration? | Yes | |
9. | Are conclusions supported by results with biases and limitations taken into consideration? | Yes | |
9.1. | Is there a discussion of findings? | Yes | |
9.1. | Is there a discussion of findings? | Yes | |
9.2. | Are biases and study limitations identified and discussed? | Yes | |
9.2. | Are biases and study limitations identified and discussed? | Yes | |
10. | Is bias due to study's funding or sponsorship unlikely? | Yes | |
10. | Is bias due to study's funding or sponsorship unlikely? | Yes | |
10.1. | Were sources of funding and investigators' affiliations described? | Yes | |
10.1. | Were sources of funding and investigators' affiliations described? | Yes | |
10.2. | Was the study free from apparent conflict of interest? | ??? | |
10.2. | Was the study free from apparent conflict of interest? | ??? | |