EAL

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 compare lipid-altering effects of almond and olive oil based diets against cheese and butter-based diets.

Inclusion Criteria:

Adults with hypercholesterolemia.

Exclusion Criteria:

Medications known to alter blood lipids, present heart disease, diabetes, any other major disease or any known food allergy.

Description of Study Protocol:

Recruitment

Participants were recruited from newspaper advertisements or local physician's offices.

Design

Randomized controlled parallel intervention in 45 free-living hypercholesterolemic subjects, with initial total cholesterol (TC) levels of 251±30mg/dl, assigned to follow one of three diets enriched with almonds, olive oil or cheese and butter (control) for four weeks. Serum lipids were measured prior to assignment. Subjects were ranked from highest to lowest cholesterol levels and blocked in groups of three for random assignment to diets. Compliance was assessed by three-day diet records and verbal reports at study meetings.

Intervention

Matched background diets with isocaloric substitution of fat in 630kcal. Subjects were assigned to one of three diets which provided 450kcal of fat from olive oil, almonds or cheddar cheese and butter. Study supplements were isocaloric, isonitrogenous and were matched for carbohydrate and fat but not fiber. The composition of each study supplement is shown in the table below:

	Almond Diet	Olive Oil Diet	Cheddar/Butter Diet
Total Fat (g)	48	47.5	55.3
MUFA (g)	30	35.7	16.9
PUFA (g)	14	3.8	1.7
SFA	4	8	36.7

Statistical Analysis

ANOVA procedures for repeated measures within and between groups and post-hoc tests were used to determine difference in blood lipid response.

Data Collection Summary:

Timing of Measurements

Measurements were made at entry into the study and after four weeks of treatment.

Dependent Variables

Total cholesterol (TC)
LDL-Cholesterol (LDL)
HDL-Cholesterol (HDL)
Total cholesterol: HDL (TC: HDL)
Triglycerides (TG).

All blood lipids were measured in duplicate on plasma collected in EDTA. HDL measurements were made following precipitation with iron dextran and magnesium chloride. TC and HDL-Cholesterol were measured by an enzymatic procedure on the Spectrum analyzer. TG, corrected with a glycerol blank, were analyzed by an enzymatic procedure on the same Spectrum analyzer. These methods were standardized and met performance requirements of the Lipid Standardization Program of the Center for Disease Control (Atlanta, Georgia). LDL was estimated using the Friedewald equation.

Independent Variables

Olive oil, almond and cheddar cheese/butter (control) diets.

Control Variables

Description of Actual Data Sample:

Initial N

Attrition (final N)

45 subjects (12 males, 33 females)

Age

53±10 years

Ethnicity

Unknown

Other relevant demographics

Anthropometrics (e.g., were groups same or different on important measures)

Mean weight 66±13kg
Mean body weight at baseline was 65±13kg in the almond group
Mean body weight at 69±15kg in the olive oil group
Mean body weight at 64±11kg in the control (cheddar/butter) group.

Location

San Francisco, California

Summary of Results:

Between-Group Differences	Almond Diet	Olive Oil Diet	Cheddar/Butter Diet
	Mean±SD	Mean±SD	Mean±SD
Total cholesterol (TC) mg/dl	222±28	240±27	263±42
LDL-Cholesterol	141±25	157±21	174±39

Other Findings

There were no significant between-group differences in HDL, TG nor the TC:HDL ratio.

There was a significant change in diet from baseline including: Decreased PUFA and increased SFA intake in the cheddar cheese/butter (control) diet and decreased SFA in the almond diet. There was a significant increase in fiber intake in all three diets. Kcal were significantly increased in the olive oil diet.

Within-group analysis of plasma lipids demonstrated a significant decrease in TC, LDL and TG in the almond diet group. No significant changes in TC, LDL or TG within the olive oil and control diet groups. The diets had no effect on HDL.

Author Conclusion:

Diets supplying reasonable amounts of MUFA and low in SFA can lower TC and alleviate some of the problems of feeding very low fat diets including the decrease in HDL. Almonds are an appropriate substitute for SFA in patients who are following cholesterol-lowering diets.

Funding Source:

Industry:

Reviewer Comments:

The study actually used a quasi control since all diets were significantly different from baseline intake. Caloric intakes were significantly higher in the olive oil diet group. Fat intake was higher than most recommendations at 39%. No significant change in body weight was seen during the relatively short study period.

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?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
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)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	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 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?	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
	4.4.	Were reasons for withdrawals similar across groups?	Yes
	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?		N/A
	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?	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?	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?	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?		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
	8.3.	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?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		???
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	???