EAL

HTN: Garlic (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine whether garlic oil capsules reduce coronary heart disease risk in trained male runners.

Inclusion Criteria:

Males
17 to 45 years of age
Absence of chronic ailments
Regular long-distance running.

Exclusion Criteria:

Current intake of garlic supplements
Presence of chronic ailments.

Description of Study Protocol:

Recruitment: Recruitment initiated by contacts with Midlands region (UK) running club coaches
Design: Randomized controlled trial
Blinding used: Double-blind
Intervention: Garlic oil or placebo for 16 weeks.

Statistical Analysis

Baseline means and standard deviations of the combined garlic oil and placebo treatment group of subjects completing follow-up were compared by visual inspection to assess any bias introduced by such losses
Randomization balance was assessed between treatments for subjects completing the study and inter-relationships of variables at baseline and at the end of the trial were investigated by correlation analysis using Spearman's Rank test
Mean changes with garlic oil were compared with those with placebo using 95% confidence intervals and P-values
Statistical power calculations were not utilized to decide the numbers of subjects recruited; numbers were chosen to approximate other studies.

Data Collection Summary:

Timing of Measurements

At baseline, volunteers were allocated randomly and double-blinded to garlic oil or placebo groups
Measurements made after 16 weeks.

Dependent Variables

Blood pressure and pulse taken with medical digital blood pressure meter
Overnight fasted blood samples analyzed for vitamin E, apoprotein B, lipids
LDL calculated using Friedewald equation
Total antioxidant status measured by enhanced chemiluminescence method
Blood clotting factors (prothrombin time, partial thromboplastin time and fibrinogen) measured with Sysmex Coagulation Analyzer and platelet numbers and size with a Coulter STKS full blood count analyzer.

Independent Variables

12.3mg per day garlic oil capsules (three capsules per day) or placebo for 16 weeks
Completed one-week diet diaries were requested at each attendance to enable consistency in intakes.

Description of Actual Data Sample:

Initial N: 30 volunteers completed baseline analysis, all male
Attrition (final N): 27 males

14 in garlic oil group
13 in placebo.

Age: Mean, 28.8±8.2 years
Ethnicity: white Caucasian
Anthropometrics: There were no significant differences between groups
Location: United Kingdom.

Summary of Results:

	Garlic Oil Group Mean±SE	Placebo Group Mean±SE	Effect of Garlic Oil Mean (95% CI)	P
Pulse (beats/min)	2.0±1.3	-0.9±1.3	2.9 (-0.8, 6.7)	0.12
SBP (mm Hg)	-3.5±1.7	0.9±2.6	-4.5 (-10.8, 1.9)	0.16
DBP (mm Hg)	-3.8±1.8	-1.2±1.5	-2.6 (-7.4, 2.2)	0.27
Triglycerides (mmol/L)	-0.06±0.06	0.14±0.10	-0.20 (-0.43, 0.03)	0.09
Total Cholesterol (mmol/L)	-0.06±0.13	-0.08±0.11	0.01 (-0.34, 0.37)	0.95
HDL Cholesterol (mmol/L)	0.329±0.046	0.268±0.058	0.061 (-0.094, 0.213)	0.41
Total:HDL Ratio	-0.69±0.10	-0.58±0.11	-0.11 (-0.42, 0.20)	0.47
LDL Cholesterol (mmol/L)	-0.37±0.13	-0.44±0.14	0.07 (-0.33, 0.47)	0.71
Apolipoprotein B (mg/dl)	-0.2±2.0	1.4±2.5	-1.6 (-8.1, 4.9)	0.62

Other Findings

Questionnaire returns indicated that dose-taking and fasting instructions were well adhered to in both treatment groups
Results were null, statistically.

Author Conclusion:

In conclusion, unlike most previous trials, the present study delivered levels of garlic oil equivalent to high bulb garlic doses and focused on individuals with low coronary risk profile who are more likely to reflect the situation of the majority of the garlic-ingesting public
Favorable trends were observed for a number of risk factors and a trial of approximately 150 subjects is required to confirm or refute these findings at the 5% significance level with 80% power.

Funding Source:

Industry:

Seven Seas Ltd (Hull, UK)

Food Company:

In-Kind support reported by Industry:

Yes

Reviewer Comments:

Did not complete power calculation, so sample sizes may have been too small to detect significant differences
Compliance assessed through diet diaries.

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?		???
	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?	???
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?		???
	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%.)	???
	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?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	Yes
	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.)	Yes
	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?	Yes
	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?	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)?	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?	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?		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?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes