DLM: Plant Stanols and Sterols (2010)
The purpose of this study was to determine if a low-fat plant sterol ester (PSE)-enriched spread consumed in conjunction with a National Cholesterol Education Program (NCEP) Step 1 diet to increase fruit and vegetable intake could improve plasma lipoprotein concentrations without adverse effects on carotenoid concentrations.
- Males and females from the general population
- With moderately raised plasma cholesterol levels (more than 5.2mmol per L) and without other biochemical abnormalities
- Without previous serious illnesses
- Body mass index (BMI) no more than 30kg/m2
- Not taking lipid-lowering medications
- Not taking vitamin supplements.
- Previous critical medical history (serious illness)
- BMI higher than 30kg/m2
- Taking lipid-lowering medication
- Taking vitamin supplements
- Biochemical abnormalities other than moderately raised plasma cholesterol levels.
Recruitment
Recruited from seven different large Irish companies, using posters in the workplace, work e-mail, and so on.
Design
- Placebo-controlled crossover trial
- Individuals randomly assigned to consume placebo spread or test spread for three weeks followed by three-week washout crossover period.
Blinding Used
Double-blind.
Intervention
- Each group was given 21g portions of low-fat spread (test spread or placebo spread) for daily consumption for three weeks (in crossover design with a three-week washout period)
- Both spreads were 35% fat with similar fatty acid profiles
- The test spread contained 8.3% plant sterols
- The placebo spread contained 0.1% plant sterols
- All participants completed an initial dietary assessment, at which time they received individualized dietary advice to adhere to a low-fat (10% energy from fat) NCEP Step 1 diet and increased fruit and vegetable intake to five portions per day.
Statistical Analysis
- Two-way ANOVA was used to compare significant difference in plasma lipids and carotenoids according to spread taken and time of consumption
- Paired T-tests to determine differences in dietary intake pre- and post-intervention.
Timing of Measurements
- Three-day food diaries completed at baseline and during the last week of each dietary intervention period
- Fasting blood samples drawn at weeks zero, three, six and nine for plasma lipoprotein and carotenoid analyses.
Dependent Variables
- Dietary intake of the following nutrients measured by entering data from three-day food diaries into a computerized dietary analysis program:
- Energy
- Carbohydrate
- Protein
- Total fat
- Percent of energy from fat
- Saturated fatty acids
- Monounsaturated fatty acids
- Polyunsaturated fatty acids
- Alcohol
- Cholesterol
- Vitamin C
- Folate
- Daily intake of β-carotene was assessed using a validated food frequency questionnaire specifically designed for measuring dietary carotenoid intake.
- Plasma lipids and carotenoids were measured according to accepted standards:
- Total cholesterol
- Triacylglycerol (TAG)
- Glucose
- Apolipoprotein B
- Apolipoprotein A
- Low-density lipoprotein (LDL) cholesterol
- High-density lipoprotein (HDL) cholesterol
- Retinol
- β-Carotene
- α-Carotene
- γ-Tocopherol
- α-Tocopherol
- Lutein
- Zeaxanthin
- β-Crypyoxanthin
- Lycopene
Independent Variables
Type of spread (plant sterol or placebo).
- Initial N: 51 total (males and females)
- Attrition (final N): 48 (27 males; 21 females)
- Age: Males, 44.1±7.6 years; females, 48.5±9.8 years.
Anthropometrics
- Weight (average):
- Males: 90.22±8.65kg
- Females: 65.49±7.9kg
- BMI (average):
- Males: 27.3±2.7kg/m2
- Females: 4.6±3.1kg/m2
Location
Ireland.
Key Findings
Variables |
Placebo Spread |
Plant Sterol Spread |
||
Pre-trial (Mean ± Standard Deviation) |
Post-trial (Mean ± Standard Deviation) |
Pre-trial (Mean ± Standard Deviation) |
Post-trial (Mean ± Standard Deviation) |
|
Total cholesterol (mmol per L) |
6.19±0.63 |
6.08±0.61 |
6.18±0.69 |
5.90±0.78* |
Apolipoprotein B (mmol per L) |
1.26±0.19 |
1.23±0.17* |
1.25±0.20 |
1.18±0.22** |
LDL cholesterol (mmol per L) | 3.91±0.70 | 3.77±0.65 | 3.94±0.83 | 3.66±1.01* |
β-Carotene (nmol per L) | 690.8±459.1 | 726.4±437.0 | 671.4±418.6 | 584.8±356.7* |
Significant difference between treatments compared with pre-trial values are *P<0.05; **P≤0.0005.
- Plasma total cholesterol, LDL-cholesterol, and apolipoprotein B concentrations were significantly lower following consumption of the plantsterol spread. A significant increase was observed in the HDL:LDL cholesterol ratio following the plant sterol intervention (P<0.05). Other plasma lipoprotein concentrations did not differ significantly following treatment. Plasma β-carotene concentration was significantly reduced following consumption of the plant sterol spread.
- When plasma β-carotene concentrations were standardized according to LDL cholesterol concentrations, there was no significant effect of plant sterol-enriched spread consumption on lipid standardized β-carotene levels. Other plasma carotenoid concentrations did not differ significantly following treatment.
Pre-trial (Mean ± Standard Deviation) |
Plant Sterol Spread (Mean ± Standard Deviation) |
Placebo Spread (Mean ± Standard Deviation) |
|
Total fat (g per day) | 88.9±26.9 | 78.5±23.9* | 75.50±22.6* |
Fat intake (% energy) |
37.3±7.6 |
34.1±5.8* |
32.4±6.1** |
Saturated fatty acid (g per day) |
1.26±0.19 |
1.23±0.17* |
1.25±0.20 |
Monounsaturated fatty acid (g per day) | 26.2±8.9 | 22.8±7.8* | 22.6±8.4* |
Cholesterol (mg per day) | 281.1±124.0 | 252.0±108.7 | 232.4±94.3* |
Vitamin C (mg per day) | 91.1±66.4 | 128.1±106.7* | 128.4±89.8* |
Significant difference compared with week zero. *P<0.05; **P<0.005.
Participants consumed statistically significantly (P<0.02) more placebo spread than PSE-enriched spread. Actual plant sterol ester intake was 1.3g per day. Consistent with following the NCEP Step 1 diet, participants showed significant reduction in daily fat intake, percent of fat from energy, saturated fatty acids and monounsaturated fatty acids when consuming the placebo or PSE-enriched spreads. Consistent with increasing fruit and vegetable intake, statistically significantly more vitamin C was consumed, and non-statistically significantly more folate and β-carotene were consumed when consuming the placebo or PSE-enriched spreads.
Incorporation of PSE-enriched reduced-fat spreads into a reduced fat diet, whereas encouraging a specific increase in fruit and vegetables, was successful in lowering both plasma total and LDL cholesterol concentrations. This was associated with a small reduction in total plasma β-carotene concentrations but no effect on lipid standardized β-carotene levels. In moderately hypercholesterolemic subjects, the combination of cholesterol-lowering dietary therapy plus PSE-enriched foods may reduce the need for cholesterol-lowering drug therapy.
University/Hospital: | Unit of Nutrition, Dept of Clinical Medicine, Trinity Health Sciences Centre, St. James's Hosp. |
Appears to be a well-designed study, although the authors suggest that a more robust study design would have determined the individual and combined effects of the NCEP Step 1 diet, increased fruit and vegetable intake and increased PSE consumption.
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? | No | |
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? | Yes | |
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%.) | No | |
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? | ??? | |
6.6. | Were extra or unplanned treatments described? | ??? | |
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)? | 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? | 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? | Yes | |
10. | Is bias due to study's funding or sponsorship unlikely? | ??? | |
10.1. | Were sources of funding and investigators' affiliations described? | ??? | |
10.2. | Was the study free from apparent conflict of interest? | Yes | |