EAL

HTN: Protein (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the cross-sectional relationship between BP and intake of soy products and other food groups in Japanese adults.

Inclusion Criteria:

Cross-sectional study without specific criteria other than being participants in a health check-up program.

Exclusion Criteria:

The following were exclusion criteria for analysis:

Use of antihypertensives, oral contraceptives or hormone replacement therapy
History of cancer, angina or myocardial infarction or diabetes mellitus.

Description of Study Protocol:

Recruitment: Participants in a health check-up program provided by a general hospital between September 1996 and August 1997, who completed a self-administered questionnaire
Design: Retrospective cross-sectional study of demograhic characteristics, dietary intake focusing on soy intake and measures of BP.

Statistical Analysis

Analysis was done separately for pre-menopausal and peri- or post-menopausal women
Spearman correlation coefficients examined the associations of BP levels with intake of soy products and other food groups and nutrients
Age, BMI, smoking status, alcohol intake, salt intake and seaweeds intake were included as covariates in analysis
Potential confounders included in analysis were marital status, exercise, age at menarche, number of births, intake of other foods and nutrients.

Data Collection Summary:

Timing of measurements: BP was measured once after questionnaire was completed
Dependent variables: SBP and DBP (measured between 8:00 and 9:00 a.m., by same observer through the study using a digital recorder after five minutes of rest.

Independent Variables

Food intake per day as groups: Soy products, soy isoflavones, cereals, fish, meats, dairy, vegetables, fruits, seaweeds
Nutrient intake per day: Included macronutrients, some vitamins, some minerals.

Description of Actual Data Sample:

Initial N

794 (394 men and 400 women) completed recruitment questionnaire.

Attrition (final N)

626 (296 men and 330 women)

68 were excluded for antihypertensive medication
Two were excluded for oral contraceptive use
Six were excluded for hormone replacement therapy
29 were excluded, due to a hystory of cancer
15 for angina or myocardial infarction
48 for diabetes mellitus.

Age

50.5±7.9 years for men
42.1±5.2 years for pre-menopausal women
53.2±6.0 years for peri- and post-menopausal women.

Ethnicity

Japanese.

Anthropometrics

BMI: 23.3±2.8 for men; 21.6±2.6 for pre-menopausal women; 22.5±2.9 for peri- and post-menopausal women

Location

Gifu, Japan.

Summary of Results:

Other Findings

In men, soy product intake was moderately inversely correlated with DBP after controlling for age, total energy, BMI, smoking status and intake of alcohol, salt and seaweeds, -0.08 with P<0.05
Correlations of soy intake with SBP and DBP in pre-menopausal or peri- and post-menopausal women did not reach statistical significance
The correlation coefficients of DBP with soy product intake were significantly different between men and peri- and post-menopausal women, -0.12 and 0.19 respectively, P=0.01
In men, inverse correlations (primarily in SBP) were observed for intakes of some nutrients rich in vegetables, soy products or dairy products, however these correlations were not seen in the female populations (P<0.01 or P<0.05)
A positive correlation between cereals, potatos and starches as a food group and SBP and DBP in pre-menopausal women was observed, 0.15 for SBP and for DBP, P<0.05. This was attibuted mainly to rice intake.
Correlatins of blood pressure with soy protein or soy isoflavone intake were similar to those with soy product intake (data not shown).

Author Conclusion:

A mild effect of soy intake on blood pressure reduction in men is indicated.

Funding Source:

Government:

Ministry of Education Science, Sports and Culture

Reviewer Comments:

Measurement error from dietary food frequency questionnaire could have underestimated the correlations between soy intake and BP
The average BP for men and women were better than "normal" (under 120/40mm Hg). Thus, weak effects of soy may have been influenced by already low BP.
Authors' comment that due to limitations of diet assessment, cross-sectional design and confounding effects of unmeasured lifestyle factors, the results should not be considered definitive
BP for pre-menopausal women at baseline was lower than for men or peri- and post-menopausal women, but no stats presented.

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?		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
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		No
	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?	No
	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?	No
	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.)	Yes
	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?	Yes
	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?		???
	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.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	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?	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?	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?	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
	7.1.	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?		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)?	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?	???
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