Animal Protein Products and Hypertension/Blood Pressure (DGAC)
To evaluate the relationship between fruit and vegetable consumption and blood pressure levels at baseline in the SUN study in order to evaluate the effect of a Mediterranean diet pattern on the risk of cardiovascular disease.
- Diagnosis of cancer
- CHD or diabetes (eliminates reverse causation bias from diet changes due to diagnosis)
- Diagnosis of hypertension, including those on antihypertensive medication
- Individuals that did not report their usual blood pressure
Recruitment
Ongoing recruitment in dynamic cohort study design. Questionnaire mailed to
- Alumni of the University of Navarra living in Spain
- Highly educated subjects belonging to and Insurance Company (ACUNSA)
- Registered nurses from the Professional Association of Nurses of Navarra
Design
Cross-sectional analysis of a prospective cohort.
Blinding Used (if applicable): not applicable
Intervention
Not specified, states detailed description published elsewhere:
- Martínez-González MA, Sánchez-Villegas A, de Irala-Estévez J, Martí A & Martínez JA. Mediterranean diet and stroke: objectives and design of the SUN project. Nutr Neurosci. 2002;5:65-73.
- Sánchez-Villegas A, Delgado-Rodrígez M, Martínez-González MA & de Irala-Estévez J. Gender, age, socio-demographic and lifestyle factors associated with major dietary patterns in the Spanish project SUN (Seguimiento Universidad de Navarra). Eur J Clin Nutr. 2003;57:285-292.
- Designed in collaboration with Harvard Public School of Health
Statistical Analysis
- Food consumption adjusted for total energy intake using the residuals method. Separated into quintiles.
- Non-conditional logistic regression analysis to adjust for several variables at one time (prevalence odds ratios).
- Multiple regression analysis on self-reported SBP and DBP.
- Repeated on self-reported hypertension diagnosis or hypertension medications as a dependent variable.
- Logistic regression analysis on stratified monounsaturated fatty acid intake.
Timing of Measurements
Subjects completed food-frequency questionnaire, baseline survey and questionnaire about blood pressure.
Dependent Variables
Blood pressure
- Self-reported responses
- Usual systolic (SBP) and diastolic (DBP) blood pressure
- Systolic Categories (mm Hg): lower than 100; 101-110; 111-120; 121-130; 131-140; 141-150; 151-160; 161-175; greater than 175.
- Diastolic Categories (mm Hg): lower than 60; 61-70; 71-80; 81-90; 91-100; 101-110; 111-120; 121-130; greater than 175
- Participants asked if they have a medical diagnosis of hypertension
- No specific recommendations about timing or device used to take blood pressure
- Considered “previously undiagnosed hypertension” if
- Subject reported no medical diagnosis of hypertension AND
- Had a SBP =>140 mmHg AND/OR
- Had a DBP => 90 mmHg
Independent Variables
- Fruit, vegetable, and monounsaturated fatty acid intake
-
Dietary Assessment
- Semi-quantitative food-frequency questionnaire
- Validated in Spain
- 136 individual food items
- Standard portions specified
- Estimated average intake over the previous year
- Selection ranged from “never to almost never” to “more than 6 times per day”
- 12 items for fruits
- 11 items for vegetables
- Semi-quantitative food-frequency questionnaire
Control Variables
- Sex
- Age
- Marital and employment status
- University degree
- Weight & height
- Smoking status
- Alcohol consumption
- Physical activity
- Metabolic equivalent index = a multiple of resting metabolic rate was assigned to each activity (MET score)
- Time spent in each activity was multiplied by the MET score then summed over all the activities to get overall weekly MET hours.
- Use of medication
- Family history of CHD
- Cancer and other diseases
Initial N: 8830 were first participants of the cohort, received questionnaires
Attrition (final N): 4393 remained after exclusion criteria applied
Age: See below
Ethnicity: not mentioned
Other relevant demographics: see below
Anthropometrics:
Location: Spain
|
Subjects included in analysis |
Participants (n) |
4393 |
Median vegetable consumption |
451.7 g/d |
Median fruit consumption |
262.6 g/d |
Age |
38.3 years |
Sex |
65.8 % female |
BMI |
23.1 kg/m2 |
Physical activity during leisure time in metabolic equivalents |
19.8 hours/week |
Energy-adjusted alcohol consumption |
6.3 g/d |
Energy-adjusted sodium consumption |
4258 mg/d |
Total fat intake |
37.1 % of total energy |
Monounsaturated fatty acid intake |
16.0% of total energy |
Saturated fatty acid intake |
12.6% of total energy |
- Age & female sex were positively correlated with fruit & vegetable consumption.
- Alcohol & sodium intake were negatively correlated with both food groups.
- Total fat intake inversely correlated with fruit & vegetable consumption; monounsaturated fatty acid intake did not change with vegetable consumption.
- BMI & physical activity not related to fruit & vegetable intake.
- Undiagnosed hypertension decreased with increasing fruit & vegetable in those with low monounsaturated fatty acid intake; relation null with high monounsaturated fatty acid intake.
- Higher monounsaturated fatty acid intake associated with decreased undiagnosed hypertension, even with lower fruit & vegetable intake.
Distribution by quintiles of energy-adjusted vegetable and fruit consumption
|
Q1 (lowest) |
Q2 |
Q3 |
Q4 |
Q5 (highest) |
Median vegetable consumption |
240 |
343 |
452 |
608 |
957 |
Subjects (n) |
878 |
879 |
880 |
878 |
878 |
Sex (% female) |
49 |
62 |
65 |
72 |
79 |
Energy-adjusted alcohol consumption |
7.3 |
6.0 |
6.9 |
5.8 |
5.3 |
Energy-adjusted sodium consumption |
4504 |
4410 |
4555 |
4405 |
4045 |
Total fat intake (% of total energy) |
37.7 |
38.0 |
36.9 |
37.1 |
35.5 |
Monounsat. Fatty acid intake (% of total energy) |
15.9 |
16.4 |
16.0 |
16.3 |
15.5 |
Saturated fatty acid intake (% of total energy) |
13.5 |
13.1 |
12.5 |
12.4 |
11.5 |
Median fruit consumption |
114 |
174 |
263 |
406 |
726 |
Subjects (n) |
878 |
879 |
879 |
879 |
878 |
Sex (% female) |
54 |
61 |
65 |
72 |
76 |
Energy-adjusted alcohol consumption |
8.3 |
6.5 |
6.3 |
5.7 |
4.5 |
Energy-adjusted sodium consumption |
4630 |
4638 |
4426 |
4288 |
3938 |
Total fat intake (% of total energy) |
39.3 |
38.6 |
37.7 |
36.2 |
33.5 |
Monounsat. Fatty acid intake (% of total energy) |
16.7 |
16.6 |
16.4 |
15.7 |
14.5 |
Saturated fatty acid intake (% of total energy) |
13.7 |
13.3 |
12.8 |
12.1 |
11.0 |
Adapted from table 2 & 3 of article
|
Q1 (lowest) |
Q2 |
Q3 |
Q4 |
Q5 (highest) |
Median vegetable consumption (g/d) |
240 |
343 |
452 |
608 |
957 |
Participants (n) |
878 |
879 |
880 |
878 |
878 |
Cases of undiagnosed hypertension (n) |
61 (6.9%) |
45 (5.1%) |
45 (5.1%) |
33 (3.8%) |
33 (3.8%) |
Median fruit consumption (g/d) |
114 |
174 |
263 |
406 |
726 |
Participants (n) |
878 |
879 |
879 |
879 |
878 |
Cases of undiagnosed hypertension (n) |
53 (6.0%) |
46 (5.2%) |
41 (4.7%) |
40 (4.6%) |
37 (4.2%) |
A diet rich in fruits and vegetables is associated with a lower blood pressure level in a Mediterranean free-living population with an abundant intake of both fat and plant-derived foods.
Government: | Dept. of Health of the Navarre Regional Government (Spain), Spainish Ministry of Health |
- The methods were not published with this article
- 50% of questionnaires analyzed after exclusion criteria applied.
- Self-reported blood pressure
- Authors notes study flaws such as including only individuals not previously labelled as diseased and high percentage of non-response, strengths include the relatively homogeneous population, adjusted for known HTN risk factors and increased internal validity due to highly selected population
Quality Criteria Checklist: Primary Research
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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) | N/A | |
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) | N/A | |
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? | Yes | |
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? | Yes | |
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? | 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? | 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? | ??? | |
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? | No | |
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)? | 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? | N/A | |
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 | |