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DLM: Almonds (2009)

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

To determine whether the effects on plasma lipids and LDL oxidation would differ between diets containing whole almonds or almond oil.
Inclusion Criteria:

Male & female volunteers

Plasma cholesterol <5.2 mmol/L

Exclusion Criteria:
  • Having diabetes, heart disease or other major illness.
  • Smoking
  • Dietary restrictions/food allergies
  • Using meds affecting lipid metab.
Description of Study Protocol:

Randomized crossover design

  • 7 day baseline
  • 6 wk periods on almond diets

Diets:

  •     50% each subj’s usual fat intake replaced with almond sources
  •      mean almond intake 66 g (35 g fat)
  •      mean almond oil intake 35 g

Dietitian assisted subj in making substitutions needed

Subj required to maintain bd wt  & activity level.
Data Collection Summary:

Compliance assessed by dietary records & return of empty containers

Weighed weekly & re-instructed

12 hr. fasting blood collected at end of baseline and each experimental period

Analyses

  • Total chols
  • LDL  chols
  • HDl chols
  • TG
  • VLDL chols
  • Apoliprprotein A and B
  • LDL oxidation: lag time, propagation rate, conjugated diene formation
Description of Actual Data Sample:
  • 12 females; 10 males
  • mean age 43.5+8 y
  • weight stable, mean BMI 23.7
  • 2 subjects withdrew  for reasons unrelated to study
Summary of Results:

Diets:

  • Almond diet sig higher  (36%) in fiber than baseline or almond oil diet
  • No sig dif in energy or lipid components

Fasting lipids

  • Almond diets vs baseline:
  • Sig lower:TC(-4% from baseline 5.35+0.13), LDL-C (-6% from 3.47+0.11)), TG  (-14% from 3.52+0.38))
  • HDL-C: sig higher  (+5% from 1.16+0.07)
  • Insig trend toward lower VLDL
  • No sig dif in Apolipoproteins or indices of LDL oxidation

Between almond diets: no sig dif in any lipid measures
Author Conclusion:
  • Whole almonds and almond oil did not differ in their beneficial effects on plasma lipids.
  • Favorable effect of almonds due to oil component.
  • Amount almonds needed for this effect easily incorporated into diets.
  • Whole almonds have other nutrients not provided by almond oil; possible benefits of these nutrients not assessed.
Funding Source:
Industry:
Almond Board of California
Commodity Group:
Reviewer Comments:

The fact that the effects were found when almonds substituted in self-selected diets suggests a durable effect that may be feasible in free-living populations.

The usefulness of the study would have been greater if more information were provided regarding how the subjects modified their diets in order to accommodate the almonds and almond oil. Apparently they reduced sources of saturated fats.  What foods were changed in order to do this and what effect would these changes have had separate from the effect of the almond additions?

It is unfortunate that the race/ethnicity of the subjects was not reported.
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? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? N/A
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? 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? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
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) 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.) 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
  3.6. 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? N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? 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
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? N/A
  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.) 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
  5.5. 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? N/A
  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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? 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
  6.7. 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? No
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? 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
  8.1. Were statistical analyses adequately described and the results reported appropriately? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? N/A
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? 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
  9.1. Is there a discussion of findings? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
10. Is bias due to study's funding or sponsorship unlikely? No
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A