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Vegetarian Nutrition

VN: Therapeutic Vegetarian Diets and Attrition (2009)

Citation:

Jenkins DJ, Kendall CW, Marchie A, Faulkner D, Vidgen E, Lapsley KG, Trautwein EA, Parker TL, Josse RG, Leiter LA, Connelly PW. The effect of combining plant sterols, soy protein, viscous fibers, and almonds in treating hypercholesterolemia. Metabolism. 2003 Nov; 52(11): 1478-83

PubMed ID: 14624410
 
Study Design:
Randomized controlled trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To assess the lipid lowering efficacy of two diets both low in saturated fat and cholesterol with one diet (portfolio diet) being rich in soy protein, viscous fibers, plant sterols, and almonds.

Inclusion Criteria:
  • Informed consent
  • Previously raised LDL-C (>4.1 mmol/L)
  • Subjects on cholesterol-lowering drugs were asked to refrain 2 weeks prior to starting study.
  • No history of CVD, DM, renal or liver disease.
  • No thyroid dysfunction.
Exclusion Criteria:
Not meeting inclusion criteria
Description of Study Protocol:

Subjects randomized to a "control" very low saturated fat dairy and whole-grain cereal diet or the portfolio diet described below (both diets vegetarian).

 

Diet Descriptions

Both diets 2000 kcal prescribed per day.

Control (NCEP Step 2 Diet):

  • <= 7% of energy from sat. fat
  • < 200mg/d cholesterol
  • High fiber

Treatment (Portfolio Diet): same as control plus the following:

  • 1.2g/1000kcal plant sterols as enriched margarine
  • 8.3g/1000kcal viscous fibers from oats, barley, psyllium
  • 16.2g/1000kcal soy protein
  • 16.6g/1000kcal unblanched whole almonds

Subjects were to consume only food prepared by the research center for the 4 week trial. Subjects given 7-day rotating meal plan and checked off each item as eaten and confirmed weight of foods.

Exercise habits were to be kept constant throughout the trial.

Data Collection Summary:

Weekly measures

Body weight, feelings of satiety, blood pressure, completed menu checklists

Biweekly measures

Fasting blood lipid profile [total cholesterol (TC), TC:HDL, LDL, HDL, LDL:HDL, triglycerides, apolipoproteins, homocystine]

Compliance to diet regimen assessed from completed checklists and return of uneaten food items.

Description of Actual Data Sample:

N: 26 healthy hyperlipidemic subjects

Final N: 25, (13 portfolio diet, 12 low saturated fat diet) one dropped out of the Portfolio diet group; (16 men/9 women)

Age: 60 ± 9.9 (range 36-85 y)

Anthropometrics and other sample information:

  • BMI 26.6 ± 2.9 kg/m2
  • On cholesterol lowering drugs prior to study (n=6)
  • Smokers allowed (n=1)
  • Recruited from hospital and newspaper ads.

Location: Toronto, Canada

Summary of Results:
Intake By Diet Group, Mean (SD)

 

Control

(Step 2)

Treatment

(Portfolio)

Energy kcal/d

2422 (121)

2426 (110)

% PRO

19.6 (0.2)

20.0 (0.1)

   % Veg. PRO

5.9 (0.1)

19.8 (0.1)*

% CHO

58.8 (0.2)

56.6 (0.3)*

% FAT

21.6 (0.2)

23.2 (0.3)*

   % SFA

4.4 (0.0)

4.9 (0.0)*

   % MUFA

8.5 (0.1)

9.5 (0.2)*

   % PUFA

7.5 (0.1)

7.9 (0.2)*

Fiber
(g/1000kcal)

26.6 (0.4)

37.2 (0.3)*

Cholesterol
(g/1000 kcal)

34 (2)

48 (1.0)*

*p<=0.001

Effect of Diet on Total Cholesterol and LDL, Mean (SD)

 

Total Chol

LDL-C

Control

mmol/L

mmol/L

Week 0

6.67 (0.16)

4.64 (0.16)

Week 4

5.99 (0.16)

4.06 (0.15)

% Diff.

-9.9 (2.0)*

-12.1 (2.4)*

Portfolio

 

 

Week 0

6.48 (0.27)

4.40 (0.27)

Week 4

4.72 (0.20)

2.81 (0.14)

% Diff.

-26.6 (2.8)*

-35.0 (3.1)*

*p<0.001 for treatment difference of control vs portfolio

Other results:

Variables

Comparison Diet

Lactoovovegetarian % Change from Baseline

Portfolio Diet

Vegan % Change from baseline

Significance of Difference between Diets

Blood Lipids

 

 

 

Total cholesterol (mmol/L)

-9.9 ±2.0§

-26.6 ±2.8§

<0.001

HDL (mmol/L)

-6.5 ±3.6

-6.1 ±3.4

ns

LDL (mmol/L)

-12.1 ±2.4§

-35.0 ±3.1§

<0.001

TC/HDL ratio -2.6 ±3.1 -20.8 ±3.6§

<0.001

LDL/HDL ratio -5.1 ±3.0 -30.0 ±3.5§

<0.001

Triglycerides (mmol/L)

+4.9 ±11.2

-6.2 ±7.8

ns

Apo A-1 (g/L)

-6.1 ±1.9#

-6.8 ±2.1#

ns

Aop b (g/L)

-8.1 ±1.9§

-26.7 ±3.3§

<0.001

Homocysteine (mumol/L)

+2.6 ±2.5

-0.7 ±4.1

ns

Lp(a) (mg/dL)

+1.6 ±2.6

-5.0 ±5.8

ns

Body Composition

 

 

 

Weight (kg)

-1.1 ±0.4*

-1.2 ±0.5*

ns

Blood Pressure

 

 

 

Systolic

-6.2 ±1.7#

-4.9 ±2.7

ns

Diastolic

-3.6 ±1.7

+4.0 ±5.4

ns

Significant change from baseline within diet group: *=P<0.05, #=P<0.01, §=P<0.001

  • Caloric intake compliance at 92±3% for Control, 86±4% for Portfolio (difference not significant, p=0.143).
  • Weight loss at 0.9±0.3kg/mo for Control, 1.0±0.4kg/mo for Portfolio (difference not significant, p=0.029).
Author Conclusion:

Combining currently recommended cholesterol lowering dietary components in amounts that were acceptable to the study subjects can produce reductions in LDL-C of 35%.

12% of the cholesterol reduction seen on this portfolio diet could be attributed to the reduction in saturated fat and cholesterol.

On the portfolio diet, the calculated coronary artery disease risk was significantly reduced by 31% (p<0.001).

Very low saturated fat diets containing foods high in viscous fibers, soy proteins, plant sterols and almonds reduce LDL-C levels to the same extent as seen in large randomized controlled trials of statins.

Funding Source:
Government: Canada Research Chair Endowment
Industry:
Loblaw Brands, Pepsico Fodos Canada--quaker peterborough Plant, Nestle Canada Inc, Procter and Gamble Canada, Barwell Food Sales Inc (Canada), Almond Board of California, Unilever R&D Vlaardingen (Netherlands)
Food Company:
Commodity Group:
University/Hospital: St Michael's Hospital (Canada), University of Toronto,
In-Kind support reported by Industry: Yes
Reviewer Comments:

Study design does not permit determination of what dietary component(s) of the portfolio diet leads to the further decrease seen in LDL over the "control" diet.

Dietary intake monitoring well designed. Many measures in place to ensure close adherence to diet protocol.

Ethnicity/race of sample not specified limiting generalizability.

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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? N/A
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? N/A
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
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
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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
  3.6. 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
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? 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
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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.) 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
  5.5. 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
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? 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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) 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? 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
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? 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? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
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? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? N/A
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? 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
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes