HTN: Garlic (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To investigate the possible effects of garlic extract consumption on blood lipid profile and oxidant-antioxidant status in normotensive and hypertensive subjects with high blood cholesterol levels.
Inclusion Criteria:
  • Volunteers with high blood cholesterol (over 5.98mmol per L), ranging in age from 24-68 years
  • Subjects with diastolic pressure value over 95mm Hg and systolic pressure value over 140 were evaluated in hypertensive group
  • Study subjects had no other complaints other than high blood cholesterol or hypertension and were not taking medication for these issues.
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:
  • Recruitment: Methods not defined
  • Design: Non-randomized clinical trial
  • Blinding used: Not applicable; lab tests
  • Intervention: Garlic extract consumption for four months
  • Statistical analysis: In the statistical analysis of the results, paired T-tests were used with values of P<0.05 considered to be significant.
Data Collection Summary:

Timing of Measurements

 Routine blood analyses completed before and after four months of garlic extract consumption.

Dependent Variables

  • Routine blood analyses including lipid parameters and liver and kidney function tests, as well as blood oxidant (malondialdehyde), oxidation resistance and antioxidant parameters (antioxidant potential, non-enzymatic superoxide radical scavenger activity)
  • Blood pressure.

Independent Variables

  • Garlic extract consumption for four months. Subjects ingested garlic extract at the dose of one ml per kg body weight per day (approximately 10g garlic per day)
  • Subjects did not use medicine during the study period and did not change dietary habits.
Description of Actual Data Sample:
  • Initial N: 23 volunteer subjects
    • 14 males
    • Nine females
    • 13 with hypertension
    • 10 normotensive.
  • Attrition (final N): 23 volunteers.
  • Age: Mean age 46.6±18.2 years 
  • Ethnicity: Not mentioned.

Other Relevant Demographics

Hypertensive group blood pressure: 98.5±22.3mm Hg DBP and 148.3±29.2mm Hg SBP

Location

Turkey.

Summary of Results:

 

Before Garlic

After Garlic

P-Value

Total Cholesterol (mmol/L)

6.97±1.56

5.23±1.4

<0.01

HDL Cholesterol (mmol/L)

0.99±0.13

1.27±0.16

<0.01

LDL Cholesterol (mmol/L)

4.55±1.3

3.07±0.91

<0.05

VLDL Cholesterol (mmol/L)

1.43±0.16

1.14±0.13

<0.05

TC/HDL ratio

7.1±1.3

4.6±1.0

<0.01

Triglyceride (mmol/L)

2.6±0.51

1.86±0.4

<0.005

Antioxidant Potential (nmol/mL/h)

35.6±8.5

48.5±9.6

<0.01

Non-enzymatic Superoxide Radical Scavenger Activity (U/mL)

8.4±1.7

13.2±1.9

<0.01

Oxidation Resistance (nmol/mL/h)

3.5±0.68

5.2±1.20

<0.05

Malondialdehyde (nmol/mL)

1.40±0.85

0.98±0.56

<0.05

 Other Findings

  • Serum total cholesterol, LDL and VLDL cholesterol and triglyceride levels were found to be significantly lowered, but HDL cholesterol increased after the extract use
  • The total-HDL cholesterol ratio was also found to be significantly decreased after the extract use
  • There were no meaningful differences with regard to other routine biochemical parameters (AST, ALT, GGT, LDH, CK, bilirubin, urea, creatinine, protein, electrolytes, calcium)
  • Additionally, blood antioxidant potential, oxidation resistance and non-enzymatic superoxide radical scavenger activity values were found increased and malondialdehyde level decreased in the second samples, relative to the first ones
  • Blood pressure values (98.5±22.3 vs. 85.1±12.4, P<0.05 for DBP and 148.3±29.2 vs. 126.2±15.6, P<0.05 for SBP) were also significantly lowered in the hypertensive group, whereas no changes (83.2±13.2 vs. 80.6±10.8, P>0.05 for DBP and 122.6±15.4 vs. 120.4±12.8, P>0.05 for SBP) were observed in the normotensive group.
Author Conclusion:
  • Our results show that increased blood antioxidant capacity and improved blood lipid profile, due to garlic extract consumption may contribute to some of the beneficial effects of garlic, with regard to atherosclerotic processes
  • We conclude that garlic extract supplementation improves blood lipid profile, strengthens blood antioxidant potential and causes significant reductions in systolic and diastolic blood pressures. It also leads to a decrease in the level of oxidation product in the blood samples, which demonstrates reduced oxidation reactions in the body.
Funding Source:
University/Hospital: Ankara University, Gazi University, Yuzuncu Yyl Univesity (all Turkey)
Reviewer Comments:
  • Recruitment and inclusion and exclusion criteria not well-defined
  • Compliance with garlic extract not monitored
  • Did not control for possible weight change or other factors.
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? ???
  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? N/A
  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? 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? 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? N/A
  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? ???
  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? No
  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? ???
  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? ???
  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)? 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? 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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes