VN: Therapeutic Vegetarian Diets and Attrition (2009)
Jenkins DJ, Kendall CW, Marchie A, Faulkner DA, Wong JM, de Souza R, Emam A, Parker TL, Vidgen E, Lapsley KG, Trautwein EA, Josse RG, Leiter LA, Connelly PW. Effects of a dietary portfolio of cholesterol-lowering foods vs. lovastatin on serum lipids and C-reactive protein. JAMA. 2003 Jul 23; 290 (4): 502-510.
PubMed ID: 12876093
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.