DF: Cardiovascular Disease (2008)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine if increased fiber-rich oat consumption, independent of weight loss, reduces BP in individuals with elevated arterial BP.
Inclusion Criteria:
  • Male
  • 50 to 75 years of age
  • BMI between 25 and 35
  • SBP 130mm to 159mm Hg or DBP 85mm to 99mm Hg
  • Sedentary or minimally physically active defined as fewer than two 30-minute aerobic exercise sessions per week.
Exclusion Criteria:
  • Overt cardiovascular, metabolic or pulmonary disease
  • Use of medication known to affect BP or pulse rate
  • Habitual intake of dietary fiber over 30g per day
Description of Study Protocol:
  • Recruitment: Recruited from the local community
  • Design: Randomized controlled trial. Subjects were screened for selection criteria and randomized to one of two groups, those receiving whole grain oat cereals or those receiving whole grain wheat cereals. The intervention was for 12 weeks.
  • Blinding used: Data collectors were blinded to group assignment of the subjects. Subjects were blinded to their BP values.


  • Oat Group: Subjects received 60g Quaker Oatmeal and 76g Quaker Oat Bran cereal, providing 14g per day of dietary fiber and 5.5g per day beta-glucan for 12 weeks
  • Wheat Group (control): Subjects received 60g Mother's Whole Wheat Hot Natural Cereal and 81g Frosted Mini-Wheats, providing 14g per day of dietary fiber for 12 weeks
  • The cereals were consumed daily at breakfast and as a snack.

Statistical Analysis

  • Repeated-measures ANOVA was used to analyze group, time and group x time interactions
  • Baseline characteristics were compared using independent T-tests.
Data Collection Summary:

Timing of Measurements

  • Resting BP was measured at baseline and following four, eight and 12 weeks of intervention
  • Ambulatory 24-hour BP measurements and urinary sodium, potassium and creatinine were obtained at baseline and following 12 weeks of intervention. 

Dependent Variables

  • Supine and seated SBP and DBP measured after more than five minutes of rest under controlled conditions. A mean of three measurements was recorded.
  • Supine and seated pulse rate
  • 24-hour ambulatory BP, night-time SBP and DBP and mean arterial pressure measured using an ambulatory BP monitor.

Independent Variables

  • Oat Group received 14g per day of fiber from oat cereals for 12 weeks
  • Wheat (control) Group received 14g per day of fiber from wheat cereals for 12 weeks.
Description of Actual Data Sample:
  • Initial N: 36 middle-aged and older men
  • Attrition (final N): 35 (data from one subject not used, due to poor compliance).
  • 50 to 75 years
  • Oat Group: 57±2 years
  • Wheat Group: 61±2 years.


Not mentioned.

Other Relevant Demographics

Sedentary or mild activity.


Baseline Oat Group
12-Week Oat Group
Baseline Wheat Group
12-Week Wheat Group
Height, cm
175 ±1.5
Weight, kg
Sum of skinfolds, mm
Waist circumference, cm

The groups were not different, however there was an effect of time for weight, BMI and sum of skinfolds for both groups, P<0.05.


Fort Collins, CO.

Summary of Results:
  • There was no change in seated or supine SBP or DBP for either group during or following the 12-week intervention
  • 24-hour SBP and DBP did not change in either group following intervention
  • Nighttime DBP and mean arterial pressure increased in both groups from baseline (data below), P<0.01 and P<0.02, respectively.

Week 12
Night-time DBP, mm Hg
Oat Group
Night-time DBP, mm Hg
Wheat Group
Night-time mean arterial pressure, mm Hg
Oat Group
Night-time mean arterial pressure, mm Hg
Wheat Group


Other Findings

  • Both groups gained weight, BMI and sum of skin folds values from baseline, P<0.05
  • Magnesium intake increased over time and there was a group x time effect (data and P not shown)
  • No changes from baseline or between groups were noted in fasting blood glucose.
Author Conclusion:
Increased fiber-rich oat or wheat cereal intake for 12 weeks has no effect on casual or 24-hour ambulatory arterial BP in middle-aged and older men with mild-to-moderate hypertension.
Funding Source:
Government: NIH
Quaker Oates Company
Food Company:
Reviewer Comments:
  • Compliance was measured by measuring returned cereal portions and subject diet records
  • Demographic information regarding ethnicity, smoking or alcohol use is not included
  • Both groups gained weight (approximately 0.8kg) during the study
  • Suggested potential reasons for lack of effect on BP are the small dose of fiber used, weight loss may be necessary in addition to increasing fiber intake, a type II error may have caused the inability to identify BP decreases under six mm Hg.
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? ???
  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")? 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? 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
  5.1. 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
  5.3. 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? Yes
  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? ???
  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)? 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? 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