Saturated Fat

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To investigate the possibility that there is an additive effect of soy and oats on lowering total cholesterol (TC) and LDL-C as an adjunct to a Step I diet vs. oats or soy alone, on free-living postmenopausal women with hyperlipidemia.

Inclusion Criteria:

*Age>50 and/or confirmed postmenopausal status

*TC above 5.17 mmol/L (200 mg/dL)

*BMI <35

*Not on wt loss diet

*No fiber, soy or dietary sups

*No hormone-replacement therapy (HRT) or on stable dose of HRT 6 months prior to study and no plans to begin or end HRT during study

*No lipid-lowering meds

*No thyroid meds

*Agreement to maintain baseline wt by not changing activity level during study (all subjects reported sedentary to moderate activity level during screening for study)

 

*Proper completion of 3 day food diary

 

 

 

Exclusion Criteria:

*Soy, milk, or oat allergy

Description of Study Protocol:

Convenience sample from workforce and senior center.

Subjects randomly assigned to

1of 4 groups:

1.       oats/milk

2.       oats/soy

3.       wheat/milk

4.       wheat/soy

Stratified block randomization was used based on HRT status and source of recruitment.

A 9 week study.

All subjects followed Step I diet for 3 weeks prior to randomization.

Subjects continued on Step I diet while also following assigned intervention regimen which lasted 6 weeks.

All subjects saw RD weekly throughout study to assure diet adherence, proper food diary recording, wt maintenance.

Synthetic soy isoflavone intake of 58.3 mg/day.

 

 

Data Collection Summary:

No use of blinding was reported.

12 hour fasting blood lipids were measured at baseline, 3, and 9 week visits.

Serum blood soy isoflavone (genistein and daidzein) concentrations were measured at baseline, 3, and 9 weeks.

Scales were calibrated before each wt was obtained.

Primary endpoints measured were changes in TC, LDL-C, and HDL-C from week 3 to 9.

Description of Actual Data Sample:

127 free-living postmenopausal hypercholesterolemic females ages 56-76.

Subjects were mostly white, “well”-educated (education level not defined), light-to-moderate activity. Greater than 96% were non-smokers and 25% were on HRT. Mean BMI was 26.9.

 

2,500 recruitment letters sent.

267 phone screens yielded 169 baseline participants of which 42 were ineligible due to disqualifying TC levels, lipid-lowering meds, or wt loss diet.

No report of how many recruitment letters were returned or what criteria were used to select the 267 who were phone interviewed.

One subject was unable to provide final blood sample or food record.

 

Summary of Results:

1 way ANOVA:

After 3 weeks on Step I there was reduction in TC, LDL-C, TG, total fat, sat fat, and chol intake, Keys score, BMI.

After 6 weeks of intervention the differences in the 4 treatment groups were:

*No difference between blood pressure or BMI.

*Most subjects in both soy groups had serum genistein and daidzein levels but there were no soy isoflavones in the no soy groups.

*Soy had no effect on lipid reduction when the subjects without detectable isoflavones who were in the soy groups were excluded in data analyses.

2 way ANOVA:

*At end of study TC was reduced by 0.21 mmol/L (8mg/dL) in oats/soy group.

*TC was reduced by 0.24 mmol/L (9mg/dL) in oats/milk group.

*The main effect was significant (p<.02) for oats but not for soy.

*The interaction was not sig.

*LDL-C was reduced by 0.27 mmol/L (10.4mg/dL) in the oats/soy group.

*LDL-C was reduced by 0.23 mmol/L (8.9mg/dL) in the oats/milk group.

*HDL-C was unchanged in all groups.

*When subjects in the soy groups who had no measurable genistein or daidzein were excluded there remained no change in any of the study results.

*No synergistic effect of oats and soy on lowering lipids was found.

Author Conclusion:

There may be a difference in effect on blood lipids between naturally occurring vs. synthetic soy isoflavones.

TGs were slightly reduced despite increased CHO intake possibly attributed to the increased total and soluble fiber intake that accompanied the increased CHO.

In this study additional modification of the Step I diet with oats yielded improvement in blood lipids compared to Step I modified with soy.

Soy foods can be a healthy substitute for high-fat animal protein.
Funding Source:
Industry:
Quaker Oates
Food Company:
Reviewer Comments:

Limitations:

Results can be generalized to white educated females only.

Strengths:

*Study conducted very well which lead to excellent diet adherence and reliable results.

*Soy diet adherence was confirmed by serum measures.

*All 4 treatment groups were equal in clinical and dietary measures at the point of randomization.

* Food record and data analyses performed by RD.

*Stratification of HRT subjects and source of recruitment was done.

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? 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")? Yes
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%.) N/A
  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? Yes
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? 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? 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? 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? 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? 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? 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
  9.1. Is there a discussion of findings? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes