VN: Therapeutic Vegetarian Diets and Attrition (2009)
To compare the cholesterol-reducing capability of a low-fat vegetarian diet containing plant sterols, viscous fibers, soy protein and almonds with a low-fat diet plus statin medication.
Healthy males and post-menopausal females with hyperlipidemia.
- Pre-menopausal females.
- The authors noted that none of the participants had a history of:
- Cardiovascular disease
- Untreated hypertension
- Diabetes
- Renal disease
- Liver disease.
Recruitment
- Recruitment of hyperlipidemic patients at the Clinical Nutrition and Risk Factor Modification Center at St. Michael's Hospital, Toronto, Canada
- Advertisements in community newspapers.
Design
- Randomized parallel design (randomization done using a random number generator)
- Four-week intervention period
- Three groups
- Control (C): N=16
- Statin (S): N=14
- Dietary Portfolio (DP): N=16.
Blinding Used
Some aspects of the study were blinded and others were not.
- Blinded
- Patients and study personnel were blinded to type of medication
- Participants were randomized into treatment groups by the statistician
- Statistician held the code for the placebo and statin medication used in the study
- Statistician was in a separate location from the study site.
- Laboratory staff received samples labeled with participant codes and dates.
- Patients and study personnel were blinded to type of medication
- Not blinded: Dietitians checked participants' food records.
Intervention
- Routine therapeutic low-fat diet (similar to current NCEP guidelines) for one month prior to intervention
- Participants stratified based on sex and pre-treatment LDL-C level
- Randomized into one of three treatment groups
- Control diet plus placebo
- Control diet plus statin
- Dietary Portfolio diet plus placebo.
- Four-week intervention.
Diets
- Components of the C and DP diets were balanced with respect to fatty acid profile, dietary cholesterol and fiber intake
- Diets were vegetarian but not vegan (eggs and dairy products were allowed)
- Each participant's diet was calculated to achieve weight maintenance
- All foods as well as the okra to be consumed by the participants were provided (participants picked up food at weekly clinic visits)
- Participants were instructed to purchase specific fruits and non-starchy vegetables and were reimbursed on presentation of receipts
- Seven-day rotating menu plans were used by all participants with modifications made for personal preferences as long as the overall goals for the diet were met
- Non-caloric beverages were not restricted
- Participants were given self-taring electronic scales to measure all foods both prior to and during intervention.
- Control diet was based on:
- Skim milk, fat-free cheese and yogurt
- Egg substitute or egg whites
- Whole grain breakfast cereals (fiber content 2.5g per 1,000kcal)
- Whole wheat bread (fiber content 2.0g per 1,000kcal)
- High monounsaturated sunflower oil and safflower oil incorporated into prepared muffins to balance the fatty acid profile of the DP.
- Dietary Portfolio diet was based on:
- Plant sterols (1.0g per 1,000kcal) via a plant sterol-enriched margarine
- Soy protein (21.4g per 1,000kcal) using soy milk and soy meat analogs
- Viscous fibers (9.8g per 1,000kcal)
- Primarily from oats, barley and psyllium
- Additionally using eggplant (0.2g per 1,000kcal) and okra (0.4g per 1,000kcal)
- Almonds (14g per 1,000kcal)
- Eggs (one per week) and butter (nine grams per day) were provided to balance the saturated fat and cholesterol content of C diet.
Statin Therapy
- 20mg lovastatin
- Crushed and delivered in Veggiecap capsules
- One capsule per day in the evening for the 28 days of the study.
- Placebo
- Lactose and blue food coloring delivered in veggie cap capsules
- One capsule per day in the evening for the 28 days of the study.
- All capsules were dispensed by hospital pharmacy in identical containers
- Participants returned containers for capsule counts at the end of the month.
Measurements
- Weight: Measured weekly
- Blood samples
- 12-hour overnight fast prior to blood collection
- Samples taken at two-week intervals.
- Blood pressure
- Measured twice in the non-dominant arm at each clinic visit
- Mercury sphygmomanometer used by the same observer.
Food Records
- Seven-day diet histories were recorded for the week prior to beginning the intervention
- Completed menu checklists returned weekly and checked by dietitians
- Satiety ratings were recorded weekly: Used a nine-point bipolar semantic scale
- Minus four: Excessively hungry
- Zero: Neutral
- Plus four: Discomfort due to excess food intake.
Exercise
Previous week's exercise was reviewed and recorded by dietitians to ensure that it remained constant during the intervention period.
Statistical Analysis
- Change in values measured between week zero and week four:
- Body weight
- Blood lipids
- Total cholesterol (TC)
- HDL-C
- LDL-C
- Triglycerides.
- Apolipoproteins A1 and B
- Ratios
- TC to HDL-C
- LDL-C to HDL-C
- Apo B to Apo A1.
- C-reactive protein
- Blood pressure
- Calculated cardiovascular heart disease CHD risk.
- Differences between treatments were assessed by Student-Neuman-Keuls multiple range test
- Analysis of covariance was used to assess treatment interaction by treatment and sex
- Intention-to-treat analysis done by including the five participants for whom baseline values were available but who dropped out prior to the week two blood sample (two-tailed paired T-test used to assess the significance of the percentage change from baseline for these participants if it was assumed that they would have demonstrated either no change, 50% of the mean change or 100% of the mean change observed)
- Results reported as mean (SE)
- Significance: P<0.05.
Timing of Measurements
- Weekly visits to clinic
- Weight
- Blood pressure
- Menu checklists
- Satiety ratings
- Exercise level monitored.
- Blood samples collected at baseline, week two and week four.
Dependent Variables
- Serum lipids (mmol per L): TC, HDL-C, LDL-C and Triglycerides
- C-reactive protein (mg per L)
- Blood pressure (mm Hg)
- Body weight (kg).
Independent Variables
- Dietary Portfolio diet: Low-fat vegetarian diet containing specific percentages of plant sterols, viscous fibers, soy protein and almonds
- Lovastatin.
Control Variables
Most foods provided.
Initial N
55.
Attrition (Final N)
46; 25 males, 21 females.
- Four randomized participants did not start the study
- Three withdrew during first week of study (job relocation, family ill health, time commitment demands)
- Two withdrawn due to elevation of liver enzymes or muscle discomfort.
Age
59 (one) years; range, 36 years to 85 years of age.
Ethnicity
Race of Study Participants | Male | Female |
European | 21 |
20 |
East Indian | 2 |
0 |
Chinese | 1 |
0 |
Black | 0 |
1 |
Hispanic | 1 |
0 |
Location
Toronto, Ontario, Canada.