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DLM: Plant Stanols and Sterols (2010)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • To assess whether advice to consume specific daily amounts of foods high in carotenoids prevents a reduction in plasma carotenoid concentrations in subjects consuming plant sterol or plant stanol esters
  • To compare the effects on blood lipids of low-fat spreads (40% fat) containing plant sterol esters or stanol esters with those of similar phytosterol-free spreads.
Inclusion Criteria:
  • Aged 20 to 75 years
  • BMI less than 31kg per m2 
  • Total cholesterol more than 5.4 and less than 8.5mmol per L
  • TG less than 4.5mmol per L
  • Informed consent obtained.
Exclusion Criteria:
  • Taking lipid-lowering medication
  • Diabetes
  • Hyperthyroidism
  • Medications likely to affect lipid metabolism
  • History of metabolic disease.
Description of Study Protocol:

Recruitment

Public advertisements requesting subjects with known elevated cholesterol.

Design

Randomized, crossover.

Randomization

Subjects were randomly assigned to groups of six to one of the six treatment orders on the basis of a randomly-generated six-digit number containing each of the numerals one to six.

Blindng

  • Double-blind according to authors
  • Spreads were coded.

Intervention

  • Three-way crossover comparison:
    • Baseline period for one week
      • Usual diet
      • Provided control spread (control-1) to adapt to the amount required for study
    • Assigned to consume 25g per day of the following test margarines (31 to 36% fat) for three weeks each instead of their usual spread:
      • Sterol-free spread (control-1)
      • Plant sterol ester spread (sterol ester-1): provided 2.3g total sterols
      • Plant stanol ester spread (stanol ester-1): provided 2.5g total stanols
      • Advised to consume at least five servings of fruits and vegetables and to eat at least one of the five servings from a list of high carotenoid foods (carrots, sweet potatoes, pumpkins, tomatoes, apricots, spinach, broccoli)
    • Follow up period for two weeks: Usual diet
  • Two-way comparison
    • Baseline period for one week: Usual diet
    • Assigned to consume 25g per day of the following test margarines (64% fat) for three weeks each:
      • Sterol ester-2: provided 2g total sterols
      • Sterol free (control-2)
      • Advised to consume at least five servings of fruits and vegetables and to eat at least one of the five servings from a list of high carotenoid foods (carrots, sweet potatoes, pumpkins, tomatoes, apricots, spinach, broccoli)
    • Follow up period for two weeks: Usual diet.

Statistical Analysis

  • Repeated measures of analysis of variance was calculated with the type of spread in each intervention arm as the within-subject factor and with sex and order as the between subject factors
    • Age, baseline LDL cholesterol and BMI were covariates in the model
  • If significant treatment effect was detected by repeated measures ANOVA, main effects were located by paired Student's T-tests and a Bonferroni correction was used to adjust for multiple comparisons
  • Further ANOVAs were run with dietary fat, saturated fat and energy intake as covariates
  • Bivariate correlation was conducted with the use of Pearson's correlation coefficient
  • Significance was set at P<0.05.
Data Collection Summary:

Timing of Measurements

  • Baseline
    • Blood samples taken on two days at the end of the period
      • Plasma lipids
  • After each three week intervention
    • Blood samples taken on two days at the end of the period
      • Plasma lipids
      • Carotenoids (three-way comparison only)
      • Weight
      • Three-day food record
  • Follow-up
    • Blood samples taken one day during the period: Plasma lipids
  • Daily
    • Consumption of test spread
    • Fruit and vegetable intake.

Dependent Variables

  • Plasma lipids
    • Total cholesterol
    • HDL cholesterol
    • LDL cholesterol
    • Triglycerides
  • Plasma carotenoids
    • Lutein
    • Retinal
    • Lycopene
    • α-carotene
    • β-carotene
  • β-carotene equivalents (measure of dietary carotenoid intake).

Independent Variables

  • Three-way comparison
    • Control-1
    • Sterol ester-1
    • Stanol ester-1
  • Two-way comparison
    • Control-2
    • Sterol ester-2.

Control Variables

  • Age
  • Baseline LDL cholesterol
  • BMI
  • Dietary fat
  • Saturated fat
  • Energy intake.
Description of Actual Data Sample:

Initial N

  • Three-way comparison: 52 men and women
  • Two-way comparison:  40 men and women.

Attrition (final N)

  • Overall
    • Nine withdrew prior to start of study
    • Two withdrew during the study
      • Unrelated hospitalization
      • Travel commitments
  • Three-way comparison: 20 men; 26 women
  • Two-way comparison: 20 men; 15 women.

Age (years, mean±SD)

  • Three-way comparison
    • Men: 55±9.7
    • Women: 58±7.3
  • Two-way comparison
    • Men: 58.1±11.0
    • Women: 56.2±7.8

Ethnicity

Not described.

Other Related Demographics

  • LDL cholesterol (mmol per L, mean±SD)
    • Three way comparison
      • Men: 6.2±0.5
      • Women: 6.1±0.6
    • Two way comparison
      • Men: 6.0±0.5
      • Women: 6.0±0.5
  • Two smokers: one male; one female
  • All women except two were post-menopausal in each comparison.

Anthropometrics

  • Weight (kg, mean±SD)
    • Three-way comparison
      • Men: 81±9.7
      • Women: 66.6±7.3
    • Two-way comparison
      • Men: 78.5±7.7
      • Women: 69.4±7.2
  • BMI (kg per m2 mean±SD)
    • Three-way comparison
      • Men: 26.6±2.8
      • Women: 25.8±2.8
    • Two-way comparison
      • Men: 25.4±1.6
      • Women: 26.8±3.0

Location

Australia.

Summary of Results:

Three-way comparison:

Variable Baseline Control-1 Sterol ester-1 Stanol ester-1 Follow-up
Total cholesterol (mmol/L)a 6.32±0.70 6.30±0.77 5.92±0.74 5.84±0.71 6.34±0.76
LDL cholesterol (mmol/L)a                                4.38±0.55 4.30±0.60 3.97±0.56 3.89±0.52 4.32±0.62
β-carotene equivalents (µg)b 4188±349 6500±527 7652±492 7533±644  

  aMean±SD   bMean±SEM

Plasma Lipids

  1. The repeated measures ANOVA for total cholesterol and LDL-cholesterol for the three test spreads was significant (P<0.001)
  2. The correlation between the change from control-1 to sterol ester-1 and control-1 to stanol ester-1 was very high (r=0.7, P<0.001), suggesting high individual repeatability of response 
  3. The reduction in total cholesterol with consumption of sterol ester-1 and stanol ester-1 was 6.1% and 7.3%, respectively, compared with consumption of control spread (P<0.001 for both)
  4. The decrease in LDL-cholesterol was 7.7% (0.33mmol per L) with sterol ester-1 and 9.5% (0.41mmol per L) with stanol ester-1 (P<0.001 for both) 
  5. The difference between the effects of sterol ester-1 and stanol ester-1 on LDL-cholesterol was not significant 
  6. Triglycerides and HDL-cholesterol were not significantly altered by the spreads
  7. Intakes of β-carotene equivalents significantly increased from the baseline period (P<0.001) by an average of 72%.

Carotenoids

  1. As total cholesterol decreased with consumption of sterol or stanol spreads, plasma concentrations of a-tocopherol, lycopene and ß-carotene decreased significantly (P<0.001), so only adjusted figures were analyzed statistically 
  2. Consumption of different spreads did not significantly change retinol and lutein, which is consistent with their transport by retinol binding protein and HDL 
  3. The dietary advice resulted in an 11% increase in plasma lutein (P=0.004) a 29% increase in α-carotene (P<0.001) and a 13% increase in plasma ß-carotene in control-1 subjects (P=0.04). Plasma lycopene did not change significantly.
  4. The plasma ß-carotene concentrations of control-1 subjects did not differ significantly from those of subjects who consumed stanol ester-1 or sterol ester-1, which was achieved by an increase of one daily serving of high-carotenoid vegetables or fruit. 
  5. Intake of β-carotene equivalents increased by 80% (P<0.001) in accordance with dietary advice.

Two-way comparison:

Variable Baseline Control-2 Sterol ester-2 Follow up
Total cholesterol (mmol/L)a 6.06±0.71 6.03±0.71 5.63±0.67 6.27±0.66
LDL cholesterol (mmol/L)a 4.16±0.58 4.16±0.58 3.76±0.60 4.25±0.49
β-carotene equivalents (µg)b 4216±442 8280±960 6882±790  

aMean±SD   bMean±SEM, significantly different from baseline (P<0.01) for all treatments.

  1. Repeated measures ANOVA for total cholesterol and LDL-cholesterol was significant (P<0.001) 
  2. Total cholesterol and LDL-cholesterol fell by 6.4% and 9.6% (0.40mmol per L), respectively, with sterol ester-2 compared with control-2 
  3. There were no significant changes in HDL-cholesterol or triglycerides.

Other Findings

  • Compliance (mean consumption)
    • Three-way comparison
      • Control-1: 24.5g per day
      • Sterol ester-1: 24.7g per day
      • Stanol ester-1: 24.9g per day
      • Minimum intake: 22.6g per day
    • Two-way comparison
      • Control-1: 23.1g per day
      • Sterol ester-2: 23.2g per day
      • Minimum intake: 16.5g per day.
  • Energy/fat intake
    • Three-way comparison
      • Energy tended to decrease from the baseline period and this decrease was significant for the control-1 period.
      • Percentage of energy from fat also decreased significantly from baseline to all intervention periods (P<0.01)
    • Two-way comparison
      • The percentage of energy from fat and saturated fat decreased (P<0.01) from baseline to the spread periods.
Author Conclusion:
  • Despite suggestions that phytosterol-containing spreads may not be effective for persons consuming low fat, low cholesterol diets, we found a 7.7 to 9.6% reduction in LDL-cholesterol in the context of diets consistent with American Heart Association guidelines. This reduction occurred for all spreads and no significant differences were observed between stanols or sterols or moderate-fat or low-fat spreads. 
  • The finding that an increase in dietary carotenoid intake negated a potential decrease in plasma carotenoids in subjects consuming either sterol ester-2 or stanol ester-1 has not been shown previously 
  • In summary, low-fat sterol- and stanol-containing spreads lowered plasma LDL concentrations by 7.3 to 9.4% in subjects consuming a low fat diet. The daily consumption of an average of one extra daily serving of a high-carotenoid fruit or vegetable elevated plasma concentrations of lipid-standardized plasma carotenoids in subjects consuming sterol-enriched spreads.
Funding Source:
Government: CSIRO Health Sciences and Nutrition (Australia)
Industry:
Unilever (Netherlands), Van den Berg Foods (UK), Flora Foods (Australia)
Food Company:
In-Kind support reported by Industry: Yes
Reviewer Comments:
  • Well-controlled study with high compliance rates
  • Unclear information:
    • When did subject withdrawals occur: prior to baseline period or during baseline period?
    • Which study (three- way or two-way comparisons) were these subjects assigned?
    • Similarly, two subjects withdrew during the study and it is unclear which study (three-way or two-way comparisons) these subjects were assigned and at what point withdrawal occurred. Subjects who completed all interventions were included in analysis.
  • Washout periods not addressed by authors.

 

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? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? 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
  2.2. Were criteria applied equally to all study groups? 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
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
  3.2. 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.) 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
  3.5. 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? ???
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  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
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? 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
  5.4. 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? Yes
  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
  6.4. 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? 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? Yes
  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? 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
  7.4. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? 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
  8.1. 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
  8.3. 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
  8.5. 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
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
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