Vegetarian Nutrition

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Aarnio K, Lindeman M. Magical food and health beliefs: a portrait of believers and functions of the beliefs. Appetite. 2004 Aug; 43 (1): 65-74.

PubMed ID: 15262019
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

This paper describes two studies. The research purposes stated for each study are as follows.

  • Study One: To delineate a portrait of people who are attracted to magical beliefs about food (MFH = Magical Food & Health beliefs)
  • Study Two: To investigate the self-reported functions for the food beliefs.
Inclusion Criteria:
  • Finnish men and women
  • Students or employees affiliated with several universities and vocational schools in Finland.
Exclusion Criteria:
  • Students with missing data on questionnaires in Study One
  • No other exclusion criteria were specified for either study.
Description of Study Protocol:

Recruitment

Study One

  • Procedure
    • Participants were recruited through six universities and 10 vocational schools in Finland
    • Recruitment message sent via e-mail to students on a student e-mail list
      • 54 e-mail lists were used
      • 16,000 subscribed members.
    • When e-mail lists were unavailable, a school employee posted the recruitment information on a communication board (either real or virtual): Potential of 4,000 students at these institutions
    • Oral recruitment announcement concerning the study prior to a lecture: 280 students.
  • Information provided to participants
    • Participants were told that the study concerned beliefs, personality and cognition
    • Participants were provided with contact information and names of researchers
    • Confidentiality and voluntary nature of study was stressed
    • By taking part in the study, participants were told they had a chance to win a prize
    • Participants were promised feedback on their responses approximately two months after their participation
      • Required that participant reveal a pseudonym, but not their identity
      • Feedback consisted of:
        • A general description of the phenomena studied
        • Absolute scale ranges and means
        • Participant's own score on each scale.
  • Respondents were given between one and three weeks to participate in the study
  • Researchers made efforts to:
    • Prudently choose their words
    • Stress that the results were based on the participant's self-description.

Study Two

  • Procedure
    • Participants were recruited from psychology courses at the University of Helsinki and the Open University of Helsinki, Finland
    • Students selecting a vegetarian dish in a student restaurant at the University of Helsinki were asked to participate.
  • Participants were told that:
    • The study concerned personality and attitudes toward food and health
    • Participation was voluntary
    • All information would remain confidential.

Design

Cross-sectional study.

Blinding Used

All responses were stored in a relational database and all data transmissions were encrypted to ensure confidentiality.

Intervention

Study One

  • Participants were asked to complete a web survey assessing the following:
    • Eating status
    • Magical beliefs about food
    • Attitude toward alternative medicine
    • Negative life events
    • Desirability of control
    • Intuitive thinking.

Study Two

  • Participants were asked to complete the questionnaires used in Study 1 plus the following:
    • Eating disorder symptoms
    • Functions of MFH beliefs.

Statistical Analysis

Study One

  • Correlations between variables
  • Standard multiple regression analyses
  • Statistical significance: P<0.05.

Study Two

  • Correlations between variables
  • Standard multiple regression analyses
  • One-way within participants ANOVA followed by planned pair-wise comparisons
    • Epsilon-corrected test
    • Greenhouse-Geisser test.
  • Statistical significance: P<0.05.
Data Collection Summary:

Timing of Measurements

Study One

Participants were given one to three weeks to complete a web survey assessing the following:

  • Eating status
    • I am omnivorous
    • I avoid eating red meat
    • I eat only fish and vegetarian food
    • I am a vegetarian
    • I am a vegan.
      • Statements One and Two were categorized as omnivores
      • Statements Three, Four and Five were categorized as vegetarians.
  • Magical beliefs about food
    • Assessed by the Magical Beliefs About Food and Health Scale
      • Scale includes 17 items on magical thinking: Most follow the law of similarity or contagion
      • Items on the scale include
        • General magical beliefs (with no specific reference to animal content)
        • Animal products as contaminants of food or personality
        • Filler items (five questions)
      • Rating
        • All statements rated on a five-point scale from strongly disagree ("1") to strongly agree ("5")
        • Total score calculated by averaging all items.
  • Attitude toward alternative medicine
    • Participants indicated their belief in alternative medicine treatments on a six-point scale
      • "0" (I do not know the therapy)
      • "1" (I do not believe in the therapy at all)
      • "5" (I strongly believe in the efficacy of this therapy)
      • "0" was scored as "1"
      • Scores were averaged into a sum score.
    • 12 treatments were listed
      • Chiropractic treatments
      • Acupuncture
      • Homeopathy
      • Nature medicine (herbs)
      • Large doses of vitamins or micronutrients
      • Treatments of magnetic fields or Kirlian photography
      • Meditation and/or mental imagery
      • Stone therapy
      • Color therapy
      • Psychic healing
      • Macrobiotics
      • Living, unheated food .
  • Negative life events
    • Participants were asked whether they had ever and how many times they had experienced these traumatic events:
      • Death of a close relative or friend
      • Serious illness of a close relative or friend
      • A life-threatening situation (e.g., an accident or fire)
      • Rape, incest, physical assault or robbery.
    • Participants were asked if they had recently experienced any of these acute crisis situations:
      • Menopause or mid-life crisis (in Finland this is commonly expressed as a crisis of 30- or 40-year olds)
      • Divorce
      • Infidelity
      • Children leaving home
      • Notice to quit or unemployment
      • Economical difficulties
      • Requalification or change of profession
      • Some other crisis.
    • Scores were added together to get the amount of negative life events.
  • Desirability of control
    • Desirability of control scale was used to evaluate participants' motivation to control events in their lives
      • Includes 20 seven-point items
      • Rating scale from "1" (The statement doesn't apply to me at all) to "7" (The statement always applies to me)
      • Sample question is "I enjoy making my own decisions."
  • Intuitive thinking
    • Assessed by the experientiality scale of the Rational-Experiential Inventory (REI-R)
      • 20 five-point items
      • Rating scale from "1" (Strongly disagree) to "5" (Strongly agree)
      • Sample question is "I believe in trusting my hunches."

Study Two

  • Qustionnaires were the same as those described in Study One for:
    • Eating status
    • MFH beliefs
    • Desirability of control
    • Intuitive thinking
    • Negative life events.
  • The Attitude Toward Alternative Medicine questionnaire contained slightly changed treatment offerings:
    • Chiropractic treatments
    • Naprapathic treatments
    • Acupuncture
    • Homeopathy
    • Natural vitamins or other natural cures
    • Large doses of vitamins
    • Treatments of magnetic fields or Kirlian photography
    • Primal therapy or Rosentherapy
    • Meditation
    • Stone or color therapy
    • Psychic healing or shamanism
    • Lifestyle diets.
  • Additional questionnaires included:
    • Eating disorder symptoms
      • Assessed by 26-item abbreviated version of the Eating Attitudes Test (EAT)
      • Rating scale from "1" (never) to "6" (always)
      • Sample statement: "Find myself preoccupied with food"
    • Functions of MFH beliefs
      • Assessed with a Function Scale
        • Includes six functions, each presented below with a sample statement
          • Control ("These beliefs have clarified my view of the world")
          • Social identity ("It is important for me to belong to a group of people who think this way")
          • Value-expressive ("My beliefs reflect my personal values")
          • Self-esteem ("My beliefs give me a feeling that I am a good person")
          • Defensive ("My beliefs protect me from some anxiety")
          • Utilitarian ("I might avoid something negative by thinking like this").
        • Rating scale: "1" (does not reflect my opinions at all) to "5" (reflects my opinions very well)
        • Function scale was presented after the MFH scale was completed
        • Participants were told to fill in the scale if they at least partly agreed with any of the statements
        • Six MFH statements were repeated and evaluated separately:
          • Two items on general magical beliefs
          • Two items on animal products as food contaminants
          • Two items on animal products as personality contaminants.

Dependent Variables

MFH beliefs.

Independent Variables

  • Age
  • Gender
  • Vegetarianism
  • Alternative medicine
  • Negative events
  • Desire for control
  • Intuitive thinking
  • Desire for control and negative life events interaction variable
  • Eating disorder symptoms (only in Study Two).

Control Variables

Controlled for statistically using multiple regression analysis of results.

Description of Actual Data Sample:

Study One

  • Initial N: 3,282 (74% female)
  • Attrition (final N): 3261(21 participants excluded due to missing data)
  • Age: 24±5.67 years (range 15 - 60 years)
  • Ethnicity: Finnish
  • Other relevant demographics
    • Educational status
      • 85% of all participants reported being full-time students
        • 77% were university students
        • 23% attended vocational school
      • Wide variety of disciplines reported
        • Social sciences
        • Natural sciences
        • Law
        • Medicine
        • Behavioral sciences
        • Technology
        • Agriculture
        • Arts
        • Humanities
        • Business
        • Service.
    • Occupational status: 9% of all participants were employed full-time.
  • Anthropometrics: No specific information was provided on anthropometric measures
  • Location: Finland.

Study Two

  • Initial N: 189 (84% were female)
  • Attrition (final N): 189
  • Age: 26.74±8.88 years (range 18 - 66 years)
  • Ethnicity: Finnish
  • Other relevant demographics
    • Status
      • 75% were full-time students: 10 fields of study
      • 25% participants were employed.
  • Anthropometrics: No specific information was provided on anthropometric measures
  • Location: Finland.

 

Summary of Results:

Main Findings

  • According to this study, the portrait of believers in magical food and health beliefs is:
    • Female rather than male
    • Vegetarian rather than omnivore
    • Relied more on alternative medicine
    • Thought in a more intuitive way
    • Demonstrated more eating-disordered thinking
    • Experienced slightly more negative life events (demonstrated in Study One).
  • The most important function for MFH beliefs was the value-expressive function.

Study One

  • MFH beliefs were associated with:
    • Female gender
    • Vegetarianism
    • Positive attitude toward alternative medicine
    • Negative life events
    • Intuitive thinking.
  • All independent variables contributed significantly to the prediction of MFH beliefs [R2=0.33, F(7,3046)=217.75, P<0.001]
  • There was no correlation between desire for control and MFH, but acted by suppressing irrelevant variance in the other independent variables
  • Age was not correlated with beliefs.

Correlations Between Variables in Study One

Variable MFH Beliefs Gender Vegetarianism Alternative Medicine Negative Life Events Desire for Control
Gender
-0.17***
 
 
 
 
 
Vegetarianism
0.38***
-0.10***
 
 
 
 
Alternative Medicine
0.44***
-0.14***
0.10***
 
 
 
Negative Life Events
0.11***
0.00
0.02
0.14***
 
 
Desire for Control
-0.03
0.05**
0.05**
0.02
 
 
Intuitive Thinking
0.26***
-0.18***
0.07***
0.33***
0.11***

0.09***

 

**P<0.01
***P<0.001.

Multiple Regression Analysis for Variables Predicting MFH Beliefs in Study One


Variable B Beta T
Gender
-0.08
-0.07
-4.27***
Vegetarianism
0.53
0.34
22.45***
Alternative Medicine
0.02
0.35
22.23***
Negative Events
0.02
0.07
4.77***
Desire for Control
-0.07
-0.07
-4.61***
Desire for control X Negative events
0.01
0.00
0.19
Intuition
0.10
0.11
6.61***

***P<0.001.

Study Two

  • MFH beliefs correlated positively with
    • Vegetarianism
    • Positive attitude toward alternative medicine
    • Eating disorder symptoms
    • Intuitive thinking.
  • The functions of MFH beliefs differed significantly from one another [F(3.846, 223.075)=34.18, P<0.001, η2 = 0.371]
  • Age was not correlated with MFH
  • Rating of importance of the MFH functions:
    1. Value-expressive (M=2.99; SD=0.13, P<0.02)
    2. Control (M=2.72; SD=0.10, P<0.02)
    3. Utilitarian (M=2.53; SD=0.09, P<0.02)
    4. Self-esteem (M=2.34; SD=0.12, P<0.02)
    5. Defensive (M=2.06; SD=0.10, P<0.02)
    6. Social identity (M=1.94; SD=0.09, P<0.02).

Correlations Between the Variables in Study Two

Variable MFH Beliefs Gender Vegetarianism Alternative Medicine Negative Life Events Desire for Control Eating Disorder Symptoms
Gender
-0.12
 
 
 
 
 
 
Vegetarianism
0.32***
-0.13
 
 
 
 
 
Alternative Medicine
0.39***
-0.02
0.08
 
 
 
 
Negative Life Events
0.13
0.04
0.07
0.19*
 
 
 
Desire for Control
0.10
0.08
-0.03
0.06
0.20**
 
 
Intuitive Thinking
0.21**
-0.19**
0.06
0.26***
0.18**
0.06
 
Eating Disorder Symptoms
0.24***
-0.11
-0.04
0.15
0.12
0.06
0.02

*P<0.05
**P<0.01
***P<0.001.

Multiple Regression Analysis for Variables Predicting MFH Beliefs in Study Two

Variable B Beta T
Gender
0.02
0.01
0.15
Vegetarianism
0.50
0.36
5.36***
Alternative Medicine
0.07
0.34
4.87***
Negative Events
0.00
-0.01
-0.18
Desire for Control
-0.03
-0.03
-0.46
Desire for Control x Negative Events
0.01
0.02
0.23
Intuition
0.13
0.13
1.91+
Eating Disorder Symptoms
0.20
0.17
2.48*

+P<0.06
*P<0.05
***P<0.001.

Other Findings

  • Age did not correlate with MFH
  • MFH believers experienced slightly more negative life events (demonstrated in Study One)
  • Believers and non-believers in MFH did not differ in desire for control
  • The same variables that corrrelated with MFH beliefs also predicted them [R2 =0.34, F(8,150)=9.18, P<0.001].
Author Conclusion:
  • Changing or preventing unfounded beliefs about food, dieting and health should take into account the emotional and value-related aspects of these issues, not simply providing scientific information
  • Affective information on food and health may be especially effective for people who are most prone to MFH beliefs; i.e., women, vegetarians, people with a positive attitude toward alternative medicine and people with eating disorder symptoms.
Funding Source:
Government: Academy of Finland (grant #200828)
Not-for-profit
Foundation associated with industry:
Reviewer Comments:
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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? 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
  3.1. 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
  3.2. 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
  3.3. 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? 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? 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.) 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
  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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) No
  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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? 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
  4.4. 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
  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. 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? 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.) 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? Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? 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
  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. 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
  6.1. 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
  6.2. 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
  6.3. 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? No
  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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? 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
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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
  8.6. 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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes