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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
0
Foundation associated with industry:
Reviewer Comments:

A table summarizing studies would have been helpful. Not a lot of detail about studies.

Quality Criteria Checklist: Review Articles
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? ???