DLM: Almonds (2009)

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

This study compares the effects of almond consumption in 2 amounts on multiple serum lipid values with those of a Step 1 diet in a well-controlled experimental setting.

Inclusion Criteria:

Study included healthy men and women ages 20-60 y.  Subjects were screened through a questionnaire, an info meeting an interview and a cholesterol screen.

Exclusion Criteria:

Fasting serum concentrations <15th or >90th percentile for age, sex, and race. Fasting triglycerides >200 mg/dL, current consumption of nuts >2x a wk, high intake of caffeinated beverages >3/day. Consumption of alcohol >2 drinks/wk, food allergies, cigarettes, chronic or metabolic disease, BMI >30 and women who had irregular menses or used hormones with past 5 years.

Description of Study Protocol:

All subjects consumed the same Western-based diet for 2 weeks prior to treatment diets to establish baseline.They were then randomly assigned to 6 possible sequences of the 3 isoenergeticdiettreatments.One diet was a Step 1 diet made of no nuts, 30% fat, The low-almond diet was 35% fat, almonds making up 10% of total calories.The high-almond diet was 39% fat, almonds making up 20% of calories.The diets were followed for four weeks each in a crossover fashion.

The high almond diet contained about 28 grams of almonds while the low almond diet contained about 34 grams.
Data Collection Summary:

Fasting blood samples were collected before breakfast on 2two days at the end of each diet cycle.The blood was sent to the lab and analyzed for concentrations of total, LDL, HDL, tricylglycerol, and glucose.Serum concentrations of apo A and apo B were also determined.

Diets were planned using Food Processor, they were then chemically analyzed to determine the exact values.
Description of Actual Data Sample:

25 participants

  • Mean age 41 + 13 yrs.
  • 11 women, 14 men
  • 10 white
  • 7 Hispanic
  • 5 Asian
  • 3 African-American
Summary of Results:

The addition of almonds had a inverse relationship with total cholesterol, LDL,apo B and the LDL:HDL ratio and Apo B:Apo Aratio.

The relationship was dose dependent.

The high almond diet produced a significant reducedin total cholesterol , LDL, apo B, when compared to the Step 1 diet.When comparedto the low almond diet there wasa significant reducedin total cholesterol , LDL, apo B,

LDL:HDL and apo B:apo A..After the high almond diettotal and LDL cholesterol was reduced 7 and 9% compared to baseline. The low almond diet produced a significant reduction in total cholesterol but not in LDL.The Step 1 diet reduced cholesterol but not significantly.The low almond diet and the Step 1 diet reduced HDL, where the high almond diet maintained HDL.
Author Conclusion:

The addition of 68 grams of almonds each day maintained HDL while lovering LDL, apo B, LDL:HDL and apo B:apo A.These effects could be attributed to the monounsaturated fat, the high amount of alphatocopherol, high arginine content and phytochemicals.By including 20% of calories in almonds the reduction in cholesterol is greater than the Step 1 diet.

The inclusion of almonds and perhaps other MUFA –rich nuts in usual or prescribed cholesterol-lowering diets may benefit both healthy persons and persons with hypercholesterolemia by reducing serum total and LDL-cholesterol concentrations and thus reducing the risk of CVD.
Funding Source:
University/Hospital: Loma Linda University
Reviewer Comments:

The conclusion that this would create the same result in subjects with hyperlipidemia may not be supported by this evidence.

The cross-over design eliminated many confounding variables.The study was supported by a grant from the Almond board of California, however it does address this issue saying that the researchers have no financial connection to the nut industry.
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? 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? 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? No
  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? Yes
  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