DLM: Almonds (2009)

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

To compare the effect of consumption of 100g of three forms of almonds (roasted salted, raw, roasted almond butter) on lipids and lipoproteins.

Inclusion Criteria:

Total cholesterol (TC) >230mg/dL and <310mg/dL.

Exclusion Criteria:

One or more of the following:

  • Major chronic disease (diabetes, heart disease, cancer)
  • Disease of the GI tract
  • Nut allergy
  • BMI>25kg/m2
  • Use of cholesterol-lowering medication, blood pressure medication, or any drug known to affect serum cholesterol.
Description of Study Protocol:

Recruitment

Done via newspaper advertising, local advertisements, and mailings and phone calls to individuals known to have high serum cholesterol from authors personal database.  

Design

Randomized trial.

Intervention

Two-week baseline period followed by four-week study diet.

Weeks one to two: Baseline period

  • Randomization at beginning of baseline period to one of three almond consumption groups (N=15 each, based on serum cholesterol levels, gender, age)
  • Participants instructed to not change their diet.

Weeks three to six: Intervention period

  • After baseline period, participants received two 50g packets of raw or roasted salted almonds, or a jar of unsalted roasted almond butter (Almond Board of California, Modesto, CA)
    • Note: Almonds and almond butter were obtained from same batch of almonds.
  • Participants received rice cakes and brown rice (Lundberg Family Farms, Richvale, CA), and lentils (Arrowhead Mills, Austin, TX) to replace animal foods with plant foods
  • Instructions and advice from RDs:
    • How to replace some of the saturated fat products and animal proteins in the diet with almonds or almond butter
    • How to keep caloric intake similar to baseline diet
    • Consumption of eggs, meat, poultry and other high-cholesterol, high-saturated fat foods was limited to ensure that dietary cholesterol, saturated fat, and trans fat intake was minimized
    • Maintain usual pattern of coffee, tea, alcohol, soft drink intake, exercise routine; not try to change weight or supplement routines.

Table. Composition of three forms of almonds (per 100g edible portion)

 

Raw Almonds

Roasted Almonds

Almond Butter

Water (g)

 4.2

1.3 

2.1 

Protein (g)

 25.3

25.4 

24.6 

Total lipid (g)

 49.5

52.5 

55.7 

  MUFA (g)

 30.7

32.1 

32.7 

  PUFA (g)

 10.6

11.4 

13.8 

  SFA (g)

 3.5

3.7 

3.9 

Carbohydrate (g)

 17.9

18.5 

14.5 

Dietary fiber (g)

 13.9

11.8 

10.5 

Vitamin E (mg ATE)

 25.3

25.5 

23.6 

  Alpha tocopherol (mg)

 24.3

24.6 

22.9 

  Beta tocopherol (mg)

 <0.05

<0.05 

<0.05 

  Gamma tocopherol (mg)

 0.98

0.88 

0.70 

  Delta tocopherol (mg)

 <0.05

<0.05 

<0.05 

Phytosterols (mg)

 113.6

125.8 

145.1 

Sodium (mg)

 <10

209 

<10 

 Note. Composition data provided by the Almond Board of California.

Statistical Analysis

  • Nutritionist V software was used to examine composition of study diets during baseline and at end of four-week period
  • Diet and weight changes from baseline to end of study diet were assessed using paired T-tests (two-tailed)
  • ANOVA was used to test for effects of study diets on serum lipoproteins and blood pressure (DVs: TC, LDL, VLDL, HDL, Tg). When a main effect was observed, T-tests for each pair of before and after scores were used to compare amount of change in each group.
    • Form of almonds (raw, roasted salted, butter) was used as a between-subjects factor
    • Time (before and after) was used as a within-subjects factor.
  • Analysis reflect those subjects who completed study (no intent-to-treat analysis used).
Data Collection Summary:

Timing of Measurements

  • Following recruitment, serum sample obtained to ensure TC>230mg/dL and to randomize subjects
  • Duplicate fasting (12-hour) serum samples (two to 10mL) were taken three to four days apart at end of baseline period and end of four-week study diet
  • Blood pressure measured in triplicate (five minutes between measurements) at baseline and end of study)
  • Four-day diet records during baseline period (reviewed by RD during second week of baseline) and last week of study
  • Subjects asked to complete weekly food frequency records during four-week study diet period.

Dependent Variables

  • Tg-analyzed using an enzymatic UV procedure on Spectrum Analyzer (Abbott Laboratories, North Chicago, Illinois)
  • TC-measured by an enzymatic procedure on Spectrum Analyzer
  • LDL-estimated according to Friedewald algorithm
  • HDL-separated from serum by a precipitation procedure using dextran sulfate and magnesium chloride.

All analysis were performed by Pacific Biometrics, Seattle, Washington.

Independent Variables

100 grams per day of almond consumption

  1. Raw unsalted almonds
  2. Roasted salted almonds
  3. Raw unsalted almond butter.

Control Variables

None mentioned in manuscript

Description of Actual Data Sample:

 

Initial N

45 adults randomized

Attrition

Seven drop-outs (authors note that drop-outs unrelated to physiological effects of almonds, mostly due to subjects inability to follow study procedures)

Final N

38 completed study (26 females, 12 males)

Mean age

61±11 years (Range: 32 to 74 years)

Ethnicity

Not reported

Anthropometrics and other relevant variables (Mean ± SD)

  • Body weight: 68±10kg
  • Total cholesterol (TC): 245±29mg/dL
  • LDL-C: 156±28mg/dL
  • HDL-C: 58±15mg/dL
  • Triglycerides (Tg):155±28mg/dL.

Location

San Francisco Bay Area, California, United States of America

Summary of Results:

 

 

Raw Almonds
(N=14)

Roasted Almonds
(N=14)

Almond Butter
(N=10)

  Basline Four weeks p Baseline Four weeks p Baseline Four weeks p
TC
(mg/dL)
247±28 230±24 ** 244±26 232±27 * 244±35 233±25 ns
LDL-C
(mg/dL)
160±25 141±16 ** 151±25 140±24 * 158±36 147±28 *
VLDL-C
(mg/dL)
29±10 29±10 ns 37±14 34±12 ns 26±8 22±5 ns
HDL-C
(mg/dL)
58±14 58±14 ns 56±18 56±21 ns 60±12 65±14 ns
Tg
(mg/dL)
143±51 158±83 ns 184±71 185±80 ns 131±42 108±26 ns
Changes in lipids and lipoproteins at baseline and week four by study group (Mean ± SD).

 

 

 

 

 

 

 

Other findings

Changes in weight, dietary intake and blood pressure over study period

  • No significant changes in body weight, caloric intake and blood pressure in any group
  • Total fat intake increased significantly in roasted almond group (P<0.001)
  • Monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) intake increased significantly in all groups (minimum of P<0.05)
  • Saturated fatty acid (SFA) intake significantly decreased in raw almond group (P<0.05)
  • Dietary fiber increased in raw (P<0.005) and roasted almond (P<0.02) groups.

 

Author Conclusion:

Plant-based diets rich in raw almonds, roasted almonds, and almond butter produce similar reductions in TC (Raw: -6.8%; Roasted: -4.9%; Butter: -4.5% but NS) and LDL-C (Raw: -11.9%; Roasted: -7.3%; Butter: -7.0%), while leaving HDL-C and Tg unchanged.

Whereas the ANOVA results show similar significant lowering of TC for all forms of almonds, the results of the paired comparisons reveal a significant decrease in TC for all three types of almonds and significant decrease in LDL for raw and roasted almonds but not almond butter. This may be partially explained by the lower sensitivity of the paired T-test with repeated measures ANOVA and the lower number of subjects in the almond butter group. Further, TC may not have decreased significantly in the almond butter group because of the slight (although non-significant) increase in HDL-C in this group.

The largest reductions in cholesterol were observed with raw almonds, however, the magnitude of the differences between raw and roasted almonds and almond butter were small (TC: -7% vs. -5%; LDL: -12% vs. -7%).

Funding Source:
Industry:
Almond Board of Canada
Commodity Group:
Reviewer Comments:

Although the authors label the study a "randomized controlled, parallel design," a control condition was not used. The results observed may be influenced by factors other than almond consumption. This design also does not allow the reader to infer the effect of almond consumption on cholesterol compared to a "general" diet.

The subjects were hypercholesterolemic, but not extremely so, with a mean age of 61 years (SD=11), and ethnicity was not reported. This limits the generalizability of the findings to older adults with TC in the range of 230-310mg/dL.

Although the sample sizes were small and limit the amount of comparisons possible, there was no examination of potential gender differences. Further, no control variables were reported as being included as factors or covariates in the main analysis.

Although subjects were informed not to change their exercise routine, no measure of compliance was reported. Given the link between lipid parameters and exercise, this is a flaw.

Intent-to-treat analysis was not used and may bias the results given the number of dropouts. Further, no analysis of dropouts was reported so it remains unclear if the individuals completing the study were different than those who did not.

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? 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? No
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
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? ???
  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
  3.5. 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? No
  4.1. Were follow-up methods described and the same for all groups? No
  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? No
  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.) No
  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? No
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? 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? 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? No
  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? 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? No
  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? 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? No
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? No