HTN: Garlic (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • The first aim was to determine if garlic supplementation in the diet of human subjects could modulate the in vivo indices of oxidative stress, thereby acting as a natural antioxidant
  • The second aim was to determine if garlic supplementation in the diet could confer beneficial effects by decreasing raised blood pressure levels in subjects with essential hypertension.
Inclusion Criteria:
  • Patients with essential hypertension as defined by JNC VI criteria, who were not on antihypertensive medication
  • Healthy age- and sex-matched controls.
Exclusion Criteria:

Previous history of coronary artery disease, secondary hypertension, diabetes mellitus, subjects on antioxidant supplements, previous history of stroke and with pre-existing or present renal insufficiency (creatinine levels above 1.8mg).

Description of Study Protocol:
  • Recruitment: Subjects were attending the Outdoor Hypertension Clinic of the Postgraduate Institute of Medical Education and Research, Chandigarh
  • Design: Non-randomized clinical trial
  • Blinding used: Lab tests
  • Intervention: Both groups given garlic pearls for eight weeks
  • Statistical analysis: The statistical significance of the garlic-pearl associated changes in the biochemical parameters was assessed by ANOVA. Differences were judged to be statistically significant if the associated P-value was less than 0.05.
Data Collection Summary:

Timing of Measurements

  • All subjects underwent a detailed clinical exam
  • Measurements made at baseline and after eight weeks of consumption of garlic pearls
  • Controls and patients called for follow-up at four weeks, when routine clinical exam and dietary compliance was checked.

Dependent Variables

  • Blood samples were analyzed for lipids, lipoprotein subfractions, plasma-oxidized LDL, plasma concentration of 8-iso-Prostaglandin F2alpha (biomarker of oxidative stress)
  • Urinary sample of 8-iso-Prostaglandin F2alpha
  • Total antioxidant status
  • Blood pressure measured as per JNC VI recommendation.

Independent Variables

  • Garlic pearls given to both groups at dose of 250mg per day for eight weeks
  • Compliance checked at four weeks
  • Subjects completed pre- and post-supplemental dietary intake records. 

Control Variables

  • Age
  • Height
  • Weight
  • Weekly alcohol consumption
  • Cigarettes smoked per week
  • BMI
  • Waist-to-hip ratio.
Description of Actual Data Sample:
  • Initial N20 patients with essential hypertension (male-female ratio, 2:1) and 20 normotensive controls (male-female ratio, 1:1)
  • Attrition (final N): See above.

Age

  • Essential hypertensives: Mean, 55 years
  • Controls: Mean, 47 years.

Ethnicity

Not mentioned.

Other Relevant Demographics

  • Essential hypertensives: Three smokers
  • Controls: Six smokers. 

Anthropometrics

Controls were age- and sex-matched.

Location

India.

Summary of Results:

 

  Baseline - EH Baseline - Controls Eight Weeks - EH Eight Weeks - Controls P-Value
SBP (mm Hg)

148±12

130±22

140±16

127±17

P<0.05

DBP (mm Hg)

94±15

76±12

85±23

74±20

P<0.05

Total Cholesterol (mg per dL)

215.4±20

180±18

206±28

176±25

NS

Triglycerides (mg per dL)

183.9±22 

158.2±19

171±20

155±25

NS
LDL-Cholesterol (mg per dL)

168±25

145±21

149±12

140±17

NS
HDL-Cholesterol (mg per dL)

40.4±23

50.3±13

43±15

50±19

NS

Other Findings

  • All participants completed trial without significant changes in body weight, diet or lifestyle and remained in good health throughout the study. Compliance was assessed as excellent. There were no differences in dietary intake of total energy, lipids, carbohydrates or protein during the study period.
  • At baseline, a moderate hypercholesterolemia and a significantly raised blood pressure was observed in hypertensive patients, as compared to controls (P<0.05). The indices of oxidative stress (plasma-oxidized LDL and plasma and urinary concentrations of 8-iso-Prostaglandin F2alpha were significantly increased in the essential hypertensive group. Further, hypertensive patients had a significantly low total antioxidant status, as compared to the control group.
  • Within two months of garlic pearl supplementation, there was a significant decline in both systolic and diastolic blood pressures (P<0.05) and a significant reduction in plasma-oxidized LDL and 8-iso-Prostaglandin F2alpha (P<0.05) in essential hypertensive patients. These values were not changed in control subjects.
  • Further, a moderate increase in the total antioxidant status was also observed in this group, as compared to their control counterparts.
Author Conclusion:
  • The findings of our study have clearly shown that patients suffering from essential hypertension are vulnerable to oxidative stress and have impaired antioxidant status
  • In the present study, we have used an entirely different preparation of garlic pearls and have demonstrated its beneficial effect in terms of effectively mitigating oxidative stress through effectively attenuating biomarkers of oxidative stress and lipid peroxidation in vivo
  • Therefore, including garlic as a daily supplement in our diet is a useful and an attractive proposition for counteracting high blood pressure and oxidative stress and various other factors associated with cardiovascular risk.
Funding Source:
Government: Indian Council of Medical Research
Reviewer Comments:
  • Authors note that the study was a double-blind RCT, but there was nothing random about the garlic supplementation treatment
  • Given male-to-female ratios and ages of groups, controls do not seem age- and sex-matched.
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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? ???
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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  3. Were study groups comparable? ???
3. Were study groups comparable? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) 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? ???
  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.) 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
  3.4. 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
  3.5. 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
  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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. 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
  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. 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
  5.1. 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
  5.2. 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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
  6.2. 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
  6.3. 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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes