EAL

HTN: Protein (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine whether soy-based diets reduce BP in mild to moderately hypertensive adults.

Inclusion Criteria:

Essential hypertension of one degree or two degrees, defined by the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (SBP 140mm to 179mm Hg and DBP between 90mm and 109mm Hg)
Half of the subjects were untreated hypertensives, the other half took antihypertensive medications.

Exclusion Criteria:

None mentioned.

Description of Study Protocol:

Recruitment: Not described
Design: Randomized, double-blind, comparative trial
Blinding used: Clinicians were blinded to which group the subject was randomized, however the subjects received either soy milk or cow's milk (placebo)
Intervention: A four-week washout period in which subjects did not take medication was followed by a three-month intervention. The soy group received soy milk (500ml bid) containing 63mg daidzein and 80mg genistein. Control group received 500ml skimmed cow's milk twice daily containing no daidzein or genistein.
Statistical Analysis: Chi-square for comparison of qualitative variables; non-paired bilateral Student's T-tests for comparison of quantitative variables and correlation/covariance analysis by Fisher's R-to-Z transform were used.

Data Collection Summary:

Timing of Measurements

BP was measured at the beginning of the three-month intervention and at the end.

Dependent Variables

SBP
DBP
Mean BP.

Independent Variables

500ml skimmed cow's milk consumed twice daily
500ml soy milk consumed twice daily.

Description of Actual Data Sample:

Initial N: 40 (25 men, 15 women)
Attrition (final N): Not discussed
Age: Males were 18 to 70 years old; females were 50 to 70. Soy group, 47.5±10.4 years; cow's milk group, 49.4±10.8
Ethnicity: Not discussed
Other relevant demographics: Following Mediterranean diet and ask not to change diet
Anthropometrics: Groups did not differ in blood pressure, sex or any other variable measured (weight, BMI, plasma lipids, ions and hormones and renal function)
Location: Unclear, but would assume Spain

Summary of Results:

At baseline SBP and DBP were not different between the soy milk and the cow's milk groups
SBP was 155±12.5 and 151.7±13.8mm Hg for the soy and cow's milk groups, respectively
DBP was 100.3±8.8 and 99.2±5.4mm Hg for soy and cow's milk groups, respectively.

Blood Pressure Change from Baseline

Author Conclusion:

Chronic soy milk consumption had modest, but significant hypotensive action in essential hypertension patients
The hypotensive action was correlated with the urinary excretion of genistein.

Funding Source:

Government:

Direccion General de Investigacion Cientifica y technica of Spain

Reviewer Comments:

Information regarding possible confounders were not discussed such as race, exercise level or change, compliance, smoking, alcohol use
Because of the differences in taste of the soy and cow's milks, the subjects were not blinded to treatment.

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?	No
	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?	N/A
	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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	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?		No
	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.)	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?	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?		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?	No
	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)?	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?	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