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Citation: 

Reference:

Morgan WA, Clayshulte BJ. Pecans lower low-density lipoprotein cholesterol in people with normal lipid levels. J Am Diet Assoc. 2000;100:312-318.


PubMed ID: 10719404
Study Design: 
Randomized Controlled Trial
Class: 
A - Click here for explanation of classification scheme.
Quality Rating: 
NEUTRAL: See Quality Criteria Checklist below.
Research Purpose: 

Purpose:

Examine the effects of the ingestion of pecan nut meats on the serum lipid profiles and dietary intakes of people with normal lipid levels who consume self-selected diets. [68 g (2 ounces) consumed daily in addition to routine diet.]

Inclusion Criteria: 

Inclusion Criteria:

Healthy with normal lipid level by laboratory analysis (total plasma cholesterol <5.17 mmol/L, <201mg/dL; LDL-C <3.36 mmol/L, <130 mg/dL; total triglycerides <2.82 mmol/L, <250 mg/dL)

Exclusion Criteria: 

Exclusion Criteria:

Active disease process, pregnancy and lactation, drug or alcohol abuse, food allergy to nut consumption, ingestion of lipid lowering medications.

Description of Study Protocol: 

Study Protocol:

Subjects were recruited by posted flyers, referrals from local health care clinics, and announcement before community groups; then randomly assigned to:

  • Control (self-selected diet with no nut consumption) or
  • Treatment group (self-selected diet with no nut consumption except for 68 g pecan nut meats/day provided by study)

Participants met biweekly with nutritionist during 8-week study to review food records, monitor compliance, and inspect pecan ration boxes.

Data Collection Summary: 

Data Collection:

Height, weight at entrance and exit, BMI calculated to monitor weight changes during course of study. Dietary data: FFQ at baseline and 3-day food diaries (1 weekend and 2 week days) at baselines and at weeks 2, 4, 6, and 8.

Blood samples obtained after 12-14 hour fast at baseline, 4 wk and 8 wk and lipids analyzed according to procedure certified according to guidelines of the National Reference System for Cholesterol.

Description of Actual Data Sample: 

Actual Sample:

  • 23 (5 men, 18 women) with noraml blood lipids enrolled.
  • 9 of 10 Control subjects (mean age 37+ 12 yr) completed (8 women, 1 of 2 men)
  • 10 of 13 Treatment subjects (mean ages 45+10 yr) completed (7 of 10 women, 3 men)
  • (83% completion rate--4 not able to comply with study protocol)
Summary of Results: 

Results:

Control Grp Pecan Grp
BMI 24+4 24+5
No change No change

Nutrient per kg body weight

  • Copper intake signif. higher in Pecan Grp at baseline
  • Pecan Grp had higher energy, total fat, monosat fat, polyunsat fat, insoluble fiber, magnesium

Total chol (mmol/L)

Baseline 4.68+0.26 4.37+0.59
4 wk 4.64+0.44 4.16+0.67
8 wk 5.02+0.54* 4.22+0.26
*Signif difference due to increase in Control Grp

LDL-C (mmol/L)

Baseline 2.74+0.26 2.61+0.49
4 wk 2.72+0.43 2.35+0.49*
8 wk 3.03+0.57* 2.46+0.59*
*Pecan Grp 10% decline at 4 wk, and 6% at 8 wk (P<.05) and signif lower than Control Grp (P<.05)

HDL-C (mmol/L)

Baseline 1.40+0.28 1.29+0.10
4 wk 1.45 +0.26 1.32+0.23
8 wk 1.47+0.34* 1.37+0.23

Triglycerides

Baseline 1.19+0.60 1.04+0.45
4 wk 1.12+0.53 1.14+0.62
8 wk 1.14+0.50 0.90+0.52
Change not significant over time

[To convert mmol/L to mg/dl multiply mmol/l by 38.9.}

*Pecan Grp significantlylower than Control at 8wk (P <.05)
Author Conclusion: 

Author's Conclusions:

Pecans can be included in a healthful diet when energy intake and potential weight gain are addressed. Findings support the hypothesis that the kind of fat in the diet (mono and poly unsaturated vs. saturated) is mor important than the total at intake.

Funding Source: 
Industry:
Western Pecan Growers Association
Commodity Group:
University/Hospital: New Mexico University
Reviewer Comments: 

Reviewer's Comments:

Self-selected diets. Pecan group had higher energy intake. Small sample size and few men. Many statistical tests increases possibility of type 1 error, as well as risk of type 2 error due to small sample size.


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?
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?
Yes
  2.2. Were criteria applied equally to all study groups?
Yes
  2.3. Were health, demographics, and other characteristics of subjects described?
No
  2.4. Were the subjects/patients a representative sample of the relevant population?
No
3. Were study groups comparable?
No
  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?
No
  3.3. Were concurrent controls used? (Concurrent preferred over historical controls.)
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 or cross-sectional 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. Criterion may not be applicable in some cross-sectional studies.)
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?
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.)
???
  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?
Yes
  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?
No
  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?
No
  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?
No
9. Are conclusions supported by results with biases and limitations taken into consideration?
No
  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
 
 
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