HTN: Garlic (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To study whether individuals with blood pressures on the lower side consume more garlic in their diets, to study the perception of the study population, whether they considered its use healthy or not and the form in which they took it (raw or cooked).
Inclusion Criteria:
Households, including children ages two to eight years.
Exclusion Criteria:
Subjects who were overweight, with known history of hypertension, diabetes mellitus, ischaemic heart disease, smoking and on medications known to effect blood pressure. 
Description of Study Protocol:
  • Recruitment: Study took place at Family Practice Center of Aga Khan University Hospital in Karachi, Pakistan
  • Design: Cross-sectional study
  • Intervention: Questionnaire was developed to estimate the dietary garlic intake per person per month and record three blood pressure readings on each individual.

Statistical Analysis

  • Total consumption in household, divided by number of subjects, in order to arrive at average consumption per month for index case
  • Sample size of 101 subjects was calculated by using population standard deviation of garlic use as 95g per person per month, with a bound on error of 20g per person per month, a level of significance of 5% and a dropout rate of 15%
  • Descriptive statistics and 95% confidence intervals for population means of garlic use were calculated for each factor.
Data Collection Summary:

Timing of Measurements

Questionnaire developed and three blood pressure readings taken per individual. 

Dependent Variables

Three blood pressure readings recorded at intervals of five minutes, according to standard protocol and average taken.

Independent Variables

Garlic consumption in the index case per month measured through questionnaire, asking questions about total garlic consumption by household, number of persons in household, number of meals taken outside and whether they consider garlic intake to be healthy.

Control Variables

Demographic variables: Age, sex, marital status, education, occupation, area of residence.
Description of Actual Data Sample:

Initial NQuestionnaire administered to 101 adult subjects

Attrition (final N): 101 subjects; 52 male, 49 female

Age

  • Under 20: Six (6.1%)
  • 20-24: 13 (13.3%)
  • 25-29: 11 (11.2%)
  • 30-34: 14 (14.3%)
  • 35-39: 13 (13.3%)
  • 40-44: 14 (14.2%)
  • 45-49: Eight (8.2%)
  • 50 and older: 19 (19.4%). 

Ethnicity

Not mentioned. 

Other Relevant Demographics

  • Households of one or two people: Three (3%)
  • Three or four: 11 (10.9%)
  • Five or six: 25 (23.7%)
  • Seven or eight: 28 (27.7%)
  • Nine or 10: 15 (14.9%)
  • 11 or more: 19 (18.8%).

Location

Karachi, Pakistan.

Summary of Results:

 

Mean Garlic Consumption

95% Confidence Interval
SBP<100

231.8±116.9

109.1, 354.4

SBP 100-120

120.1±82.1

99.8, 140.4 

SBP>120

144.7±78.8

114.8, 174.7

DBP<70

167.5±109.1

83.6, 251.4

DBP 70-90

130.6±85.8

111.8, 149.5

DBP>90

130.4±74.2

72.9, 187.4

All Factors

133.9±86.8

117.2, 151.3

Other Findings

  • An average garlic use of 134g per case per month was found
  • 67% of subjects used garlic in cooked food, while the rest used it either in the raw form or in pickles
  • 59% thought that dietary use of garlic is healthy
  • Subjects with systolic blood pressure on the lower side were found to consume more garlic in their diets (P=0.05) 
  • Those with systolic blood pressure below 100mm Hg were consuming 232g garlic per month in comparison to those with systolic blood pressure above 120mm Hg, who were consuming 148g garlic per month
  • Those with diastolic blood pressure under 70mm Hg were consuming 167g garlic per month in comparison to those with diastolic above 90mm Hg, who were consuming 130g per month.
Author Conclusion:
  • This study shows that individuals with systolic blood pressure on the lower side are more likely to consume more garlic in their diets
  • This was a pilot study and more elaborate trials are recommended to prove this association.
Funding Source:
University/Hospital: Aga Kahn University (Karachi Pakistan)
Reviewer Comments:
  • Questionnaire not shown to be valid or reliable
  • Households addressed rather than individuals and very large numbers of people in the households (up to 11 or more)
  • Authors note that estimation of garlic intake is crude
  • Specific recruitment of 101 subjects not defined.
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? 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? ???
  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? ???
  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? 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? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  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? ???
  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? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  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)? 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? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. 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