DLM: Vitamin E (2001)
Citation:
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To provide a review of studies that have addressed the role of dietary antioxidants in disease prevention.
Inclusion Criteria:
Not applicable.
Exclusion Criteria:
Not applicable.
Description of Study Protocol:
Observational Studies
- NHS: More than 85,000 nurses followed for less than eight years
- HPS: More than 39,000 males followed for four years
- NHANESI: More than 11,000 adults followed for 10 years.
Primary Prevention Trials
- ATBC: More than 29,000 male Finnish smokers followed who took 50 IU Vitamin E or 20mg beta-carotene or both or placebo, followed five to eight years
- CARET: 18,000 men and women with a history of cigarette smoking or occupational exposure to asbestos who took 30mg beta-carotene and 25,000 IU retinyl palmitate daily
- PHS: 22,071 male physicians followed for 12 years who took 325mg aspirin or 50mg beta-carotene every other day, or both daily.
Data Collection Summary:
Not applicable.
Description of Actual Data Sample:
Not applicable.
Summary of Results:
Observational Studies
- Nurses Health Study:
- Risk of cardiovascular disease is lowest in women with highest compared to those in the lowest quintile of vitamin E intake (adjusted for age and smoking). RR was 0.66 (95% CI, 0.50 to 0.87).
- No relationship between Vitamin C intake and disease.
- Health Professionals Follow-Up Study
- Showed similar results for Vitamin E
- Current and former males smokers showed a lower risk of major coronary events in those with high beta-carotene intakes compared with low intakes
- No relationship between vitamin C intake and disease risk.
- NHANES I
- Men: RR was 0.75 (95% CI, 0.53 to 0.97) in highest (50mg per day of vitamin C) compared to lowest (less than 50mg per day of vitamin C).
Primary Prevention Trials
- ATBC
- No reduction in risk of lung cancer or major coronary events with supplementation of 50mg (50 IU) of vitamin E, 20mg beta-carotene or both
- Vitamin E resulted in risk of death from hemorrhagic stroke; beta-carotene resulted in risk for ischemic heart disease.
- CARET
- Risk for cardiovascular disease and lung cancer increased in supplemented group.
- Physicians Health Study
- No significant beneficial or harmful effects of beta-carotene
- Recommendation for general population to consume a balanced diet with emphasis on antioxidant-rich fruits, vegetables and whole grains
- For secondary prevention, consider vitamin E supplementation if further studies show benefits and lack of harm.
Secondary Prevention Trials
- CHAOS
- Risk of myocardial infarction and all cardiovascular disease events were reduced by 77% and 47% in the treatment group, with a delay of approximately 200 days in the benefit of the treatment.
Effects on Clinical Outcomes
- Indian Experiment of Infarct Survival Study
- Infarct size, angina and total coronary events were reduced in patients receiving antioxidants in the post-myocardial infarction period.
Author Conclusion:
There is insufficient efficacy and safety data to recommend Vitamin E supplements for the entire poplulation and more research is warranted. However, a balanced diet is encouraged with empahsis on fruits and vegetables that are high in antioxidants.
Funding Source:
Not-for-profit |
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Reviewer Comments:
A table summarizing studies would have been helpful. Not a lot of detail about studies.
Quality Criteria Checklist: Review Articles
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Relevance Questions | |||
1. | Will the answer if true, have a direct bearing on the health of patients? | Yes | |
2. | Is the outcome or topic something that patients/clients/population groups would care about? | Yes | |
3. | Is the problem addressed in the review one that is relevant to dietetics practice? | Yes | |
4. | Will the information, if true, require a change in practice? | Yes | |
Validity Questions | |||
1. | Was the question for the review clearly focused and appropriate? | Yes | |
2. | Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? | No | |
3. | Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? | No | |
4. | Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? | No | |
5. | Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? | No | |
6. | Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? | No | |
7. | Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? | No | |
8. | Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? | No | |
9. | Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? | Yes | |
10. | Was bias due to the review's funding or sponsorship unlikely? | ??? | |