DLM: Plant Stanols and Sterols (2010)
Citation:
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine the efficacy on plasma cholesterol-lowering of plant sterol esters or non-esterified stanols eaten within low-fat foods as well as margarine.
Inclusion Criteria:
- Known hypercholesterolemia untreated with lipid-lowering drugs for preceding six months or longer
- Total cholesterol greater than 5.5mmol per L
- Triglycerides (TG) less than 3mmol per L
- Informed consent.
Exclusion Criteria:
- Hormone replacement therapy (HRT)
- Smoking
- Alcohol exceeding four drinks per day (men), two drinks per day (women)
- Medication likely to affect plasma lipids
- Bowel, liver and kidney disorders
- Thyroid dysfunction
- Diabetes mellitus.
Description of Study Protocol:
Recruitment
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Design
Randomized, crossover.
Blinding
Subjects were blinded to diet assignment.
Intervention
- Study 1:
- Two-week run-in
- Habitual diet
- Four-week control period
- Habitual diet plus test foods minus supplementation were provided
- Two four-week test periods:
- Randomization to one of the following, followed by the other dietary intervention:
- Habitual diet plus 2.4g plant sterol ester
- 50% sitosterol
- 20% stigmasterol
- 20% campesterol
- Habitual diet plus similar amount of non-esterified plant stanols
- 70% sitostanol
- 27% campestanol
- ~1% free sterols
- Habitual diet plus 2.4g plant sterol ester
- Test substances provided in three different foods: Cereal, bread, margarine
- Equal amounts of tocopherol added to all margarines
- Randomization to one of the following, followed by the other dietary intervention:
- Two-week run-in
- Study 2: Initiated several weeks after the end of Study 1
- Control period: Habitual diet
- Two four-week test periods
- Randomization to one of the following, followed by the other dietary intervention:
- Habitual diet plus 2.4g plant sterol ester-containing spread (50% fat)
- 40% butter fat and included canola oil, soybean sterol ester and trans-free palm oil blend
- 46% saturated fatty acids, 28% oleic, 17% linoleic, 3% alpha linolenic acid
- 2% trans fatty acids
- Habitual diet plus 50% fat control spread
- 40% butter fat, 32% canola oil, 8% hardened trans-free palm oil blend
- 43% saturated fatty acids, 47% mono- and polyunsaturated fatty acids
- 2% trans fatty acids
- Equal amounts of tocopherols added to margarine.
- Habitual diet plus 2.4g plant sterol ester-containing spread (50% fat)
- Randomization to one of the following, followed by the other dietary intervention:
Statistical Analysis
- Repeated measures ANOVA on ranks (Freedman), followed by pairwise multiple comparison procedures, due to absence of normal distributions for plasma total and LDL cholesterol. Data provided as medians.
- For normally distributed parameters, values are given as means
- Plasma sterols and carotenoids analyzed by paired T-test.
Data Collection Summary:
Timing of Measurements
- Study 1
- Baseline
- Three-day food frequency questionnaire (FFQ) focusing on fats, cholesterol and fiber
- Plasma lipids
- Beginning of each intervention
- Plasma lipids
- After each intervention
- Three-day FFQ focusing on fats, cholesterol and fiber
- Plasma lipids
- Plasma sterols
- Plasma carotenoids
- Plasma tocopherols
- Baseline
- Study 2
- Plasma lipids were drawn at baseline and at the beginning and end of each intervention.
Dependent Variables
- Plasma lipids (Study 1 and 2)
- Total cholesterol
- Triglyceride
- HDL cholesterol
- LDL cholesterol
- Plant sterols(Study 1)
- Campesterol
- Sitosterol
- Lathosterol: index of cholesterol synthesis (precursor of cholesterol)
- Carotenoids(Study 1)
- Lycopene
- α-carotene
- β-carotene
- β-cryptoxanthin
- Tocopherols (Study 1)
- α-tocopherol
- y-tocopherol.
Independent Variables
- Study 1
- 2.4g esterified plant sterols
- 2.4g non-esterified stanols
- Study 2
- 2.4g esterified plant sterols (dairy spread)
- Control dairy spread.
Description of Actual Data Sample:
- Initial N:
- Study 1: 22 (18 men; four women)
- Study 2: 15 (gender breakdown not provided)
- Some advised to seek more active lipid lowering medication
- Some unavailable for a further eight weeks
- Attrition:
- Study 1: 22
- Study 2: 15
- Age: 60±9 years (range 34 to 70 years)
- Ethnicity: Not described
- Other relevant demographics:
- Normotensive: None higher than145/95mmHg
- Cholesterol: 21 of 22 had cholesterol value greater than 5.5mmol per L
- Triglyeride level between 2.0 and 2.6mmol per L: Five subjects
- HDL cholesterol: None less than 1.0mmol per L
- Anthropometrics: 24±1.9kg per m2 (range 18.3 to 26.9kg per m2)
- Location: Australia.
Summary of Results:
Study 1:
Plasma Lipids Following Plant Sterol- or Stanol-Enriched Foods
Intervention | Cholesterol (mmol/L) median (25-75%) | LDL cholesterol (mmol/L) median (25-75%) |
Baseline | Not reported | Not reported |
Control | 7.0 (6.25-7.40) | 4.77 (4.0-5.35) |
Sterol esters | 6.40 (5.85-7.15) | 4.12 (3.45-5.10) |
Stanols | 6.75 (5.80-7.30) | 4.37 (3.6-4.95) |
- Median total cholesterol fell significantly by 8.5% with sterol esters and by 3.5% with the non-esterified stanol (P<0.001 by ANOVA and P<0.05 by pairwise comparison of each test intervention vs. control diet). The response with sterol esters was possibly significantly greater than with non-esterified stanol (P=0.05).
- Median LDL-cholesterol was reduced by the sterol esters (-13.6%, P<0.001 by ANOVA on ranks, P<0.05 by pairwise comparison) and by non-esterified stanols (-8.3%, P=0.003, ANOVA and P<0.05 pairwise comparison)
- The minor changes in HDL-cholesterol and TG were not significant
- With sterol esters plasma plant sterol levels rose (35% for sitosterol (P<0.01), 51% for campesterol, (P<0.001), plasma lathosterol rose 20% (P=0.03), indicating compensatory increased cholesterol synthesis
- With stanols, plasma sitosterol fell 22% (P=0.004), indicating less cholesterol absorption
- None of the four carotenoids measured in plasma changed significantly
- α- and y-tocopherols both increased in plasma with the sterol supplement: α-topherol 35.2 and 40.1µM per L; y-tocopherol 11.1 and 17.7 µM per L (61%, P=0.044).
Study 2:
Plasma Lipids Following Dairy Spread
Intervention | Total cholesterol (mmol/L) median (25-75%) | LDL cholesterol (mmol/L) median (25-75%) | Triglyceride (mmol/L) mean±sd |
Baseline | 6.65 (5.70-6.98) | 4.60 (3.67-4.85) | 1.11±0.29 |
Control dairy spread | 7.05 (6.14-7.42) | 4.90 (4.12-5.35) | 1.37±0.59 |
Sterol ester dairy spread | 6.40 (6.05-7.15) | 4.30 (3.62-4.97) | 1.36±0.50 |
- Median total cholesterol fell 8.5% on the sterol-ester fortified spread (P<0.001 by ANOVA and P<0.05 by pairwise comparison)
- Median LDL-cholesterol rose 6.5% with dairy spread and fell 12.2% with the sitosterol ester fortified spread (P=0.03 ANOVA and P<0.05 by pairwise comparison)
- HDL-cholesterol did not change between dietary changes
- Plasma triglyceride rose 23% with the dairy fat spread (P=0.017).
Other findings:
- Background diet info (Study 1) comparing beginning to end of study
- Small increase in fat consumption as energy (32 to 34%, P=0.02).
- Maintained saturated fat as energy (11.5±2%)
- Maintained cholesterol intake (164±47mg)
- Fiber (19g vs. 18g)
- Four to eight weeks after conclusion of Study 2, 13 of 15 subjects returned for re-measurement of lipids
- Mean total cholesterol: 6.69±1.1 mmol per L
- Mean LDL-cholesterol: 4.71±1.0 mmol per L.
Author Conclusion:
- This study has confirmed the substantial LDL-cholesterol-lowering effect achievable with sterol esters in moderately hypercholesterolemic subjects
- Only one-third of the sterol was in a fat spread, the remaining two-thirds having been eaten as bread and cereal. This extends the range of foods within which such cholesterol-lowering compounds may be delivered.
- The LDL-cholesterol raising effect of butter fat could be countered by including sterol esters
- Plasma carotenoids and tocopherols were not reduced in this study. This may relate to the generally high consumption of fruit and vegetables by Australians, especially those on cholesterol-lowering diets.
- This report is to our knowledge the first demonstration of the LDL-cholesterol lowering efficacy of either phytosterol esters or non-esterified phytostanols delivered in bread and cereal.
Funding Source:
Industry: |
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In-Kind support reported by Industry: | Yes |
Reviewer Comments:
- Well-controlled study. Author notes that a limitation of Study 1 is that the control foods were eaten initially by all subjects and only the two test diets were randomized.
- Per authors, washout period not considered necessary since sterols and stanols are minimally absorbed, and three to four weeks is considered adequate to reach new steady-state values for plasma cholesterol, triglyceride and HDL cholesterol.
- One subject did not meet cholesterol eligibility criterion
- Baseline plasma lipid levels not provided for Study 1. Authors reported that these were similar to those at the end of the initial control dietary period.
- Although authors reported that subjects were required to return all food packages, compliance was not reported.
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 | |
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) | No | |
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? | 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%.) | Yes | |
4.3. | Were all enrolled subjects/patients (in the original sample) accounted for? | Yes | |
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? | 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? | ??? | |
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? | 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)? | Yes | |
8.5. | Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? | No | |
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? | Yes | |
10. | Is bias due to study's funding or sponsorship unlikely? | Yes | |
10.1. | Were sources of funding and investigators' affiliations described? | Yes | |
10.2. | Was the study free from apparent conflict of interest? | Yes | |