DLM: Almonds (2009)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

The purpose of the study was to examine the effect of a portfolio diet (high in plant sterols, viscous fiber, soy protein and containing almonds) on hematologic parameters associated with CHD risk.

Inclusion Criteria:

Hypercholerolemic adults characterized by previous LDL-cholesterol >4mmol/L.

Exclusion Criteria:
  • History of CVD
  • Liver or renal disease
  • Diabetes
  • Medication known to influence serum lipids.
Description of Study Protocol:

Recruitment

35 subjects recruited from prior trial of portfolio diet; 31 subjects recruited from newspaper advertisements.

Design

Single-phase one-year open label study of a self-selected (ad libitum) dietary portfolio of cholesterol-lowering foods.

Intervention

Subjects followed a low-fat diet (mean macronutrient profiles close to current ATP III guidelines) incorporating four primary components of the dietary portfolio: 1.0g plant sterols per 1,000kcal from a plant sterol ester-enriched margarine; ~10g viscous fibers per 1,000kcal from oats, barley, psyllium, okra, and eggplant; 22.5g soy protein per 1,000kcal from soy milk and soy meat analogues; and 23g whole almonds per 1,000kcal. They were also asked to consume additional sources of plant protein and fiber in the form of dried legumes and to eat the recommended five to 10 servings of fruit and vegetables. Advice on eating a vegetarian diet without the dairy, eggs, or meat was given. Egg products were to consist of egg substitute and liquid egg whites. Any meat or dairy foods consumed were to be low-saturated-fat options. They purchased the foods from supermarkets and health food stores except for the bread which was obtained at cost from the baker and margarine which was provided to all but four subjects. 

Subjects kept a seven-day food record the week prior to each of the visits. The dietitian reviewed the records at each visit. The consumption of the four primary components of the diet were estimated from the records and expressed as a percentage of the amount recommended for that person's energy requirement. If a person felt unable to consume the full amount of one component, an attempt was made to ensure that increased amounts of the other three components were consumed. The diets were analyzed for macronutirients, fatty acids, cholesterol, and fiber with the use of a computer program based on US Department of Agriculture data.

Statistical Analysis

The results are expressed as means ± SEs. An intent-to-treat with last-observation-carried-forward analysis was performed for those subjects who did not complete the study. All statistical tests were performed at the P<0.05 significance level. The effect of change from baseline and linear trends over time from weeks zero, 24 and 52 were assessed with the use of a generalized linear mixed model. The repeated-measures analysis had percentage change from week zero as the response variable and week as the covariate predictor, with participant ID as the sole class variable. An analysis was also carried out with the use of only the 55 participants who completed the one-year study.  

Linear associations between mean LDL-cholesterol reduction and mean compliance measures were tested by using Pearson's correlation. Compliance was assessed for the four portfolio components (soy protein, plant sterols, viscous fibers, and almonds), where the prescribed amount represented 100%. Total compliance was the sum of the four individual compliances given equal weighting. 

Subjects were divided into those who met ATP III criteria for metabolic syndrome (N=18) and those who did not (N=37). Satterthwaite T-tests were performed to determine differences in response in these two groups. No assumption of equal variance was made.

Data Collection Summary:

Timing of Measurements

Weeks -six, -two, zero, two, four, eight, 12, 18, 24, 32, 42 and 52.

Dependent Variables

Hemoglobin, hematocrit, RBC count, MCV, platelet number, mean platelet volume, RBC fragioity, reticulocytes,WBC count, neutrophils (PMN) lymphocytes, PMN: lymphocyte, basophils, eosinophils.

Independent Variables

Portfolio diet.

Description of Actual Data Sample:

Initial N

N=66

Attrition (final N)

N=55 (17% attrition rate)

Age

59.5±1.2 years (range 32-86 years)

Ethnicity

Other relevant demographics

18 with metabolic syndrome

Anthropometrics

BMI 27.3±0.5kg/m2

Location

Toronto, Canada

 

Summary of Results:

 

Values are reported as mean (se)

Variable

Baseline

 

Six months

 

One year

 

P-value

 

Hgb (g/l)

143.9 (1.6)

144.1 (1.7)

142.4 (1.5)

0.013

Hct (l/l)

0.419 (0.005)

0.421 (0.005)

0.412 (0.005)

<0.001

Mean platelet volume (fl)

9.12 (0.12)

9.31 (0.15)

9.28 (0.15)

0.033

PMN (x109/l)

3.47 (0.15)

3.46 (0.15)

3.13 (0.12)

0.012

PMN;Lymphocyte

2.12 (0.13)

2.05 (0.10)

1.87 (0.09)

0.003

Other Findings

  • NS changes in MCV, platelet number, platelet fragility, RBC, WBC, lymphocytes, eosinophils
  • Change in Basophil number was significantly different (P=0.003), but not related to hypothesis
  • Magnitude of change was small, -1.5g/L for Hgb, -0.007 for Hct
  • Approximately 10% change in PMN and PMN: Lymphocyte ratio at one year
  • Response did not differ between subjects with metabolic syndrome and those without metabolic syndrome
  • 62.1±2.7% of completers (N=55) judged to have adequate compliance (similar rate 62.6%±2.7% in total group; N=66).
Author Conclusion:

Slight but statistically significant reduction in hemoglobin and hematocrit and platelet volume may decrease risk for CVD associated with blood viscosity and coagulability. Decrease in PMN may reflect modulation of inflammatory response which has been associated with risk for CVD.

Funding Source:
Government: Federal Gov. of Canada, Canadian Natural Sciences and Research Council,
Industry:
Loblaw Brands, Unilever, Almond Board of California
Food Company:
Commodity Group:
Reviewer Comments:
  • Decrease in Hgb and Hct is statistically significant but authors do not make a good argument for the physiological significance of an effect of this magnitude
  • Study design does not fit any of the categories for study type. (A-X) Closest is "C" non-randomized trial with concurrent controls (in this case, with NO controls).
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) No
  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) No
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? 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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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
  2.1. 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? 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? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? N/A
3. Were study groups comparable? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  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
  3.2. 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.) No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  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
  3.4. 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
  3.5. 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
  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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. 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
  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? No
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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.) No
  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.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? 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
  5.4. 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
  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. 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
  6.1. 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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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? No
  8.6. Was clinical significance as well as statistical significance reported? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? 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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes