EAL

DLM: Vitamin E (2001)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The purpose was to evaluate the current literature involving antioxidants and vascular disease, particularly the potential mechanism(s) of action from antioxidants.

Inclusion Criteria:

Descriptive, case control, prospective cohort, and randomized, double-blind, placebo-controlled studies of European and North American subjects.

Exclusion Criteria:

Not applicable

Description of Study Protocol:

Although an overview is presented for each study's protocol, a description is not provided for the protocol of this review.

Data Collection Summary:

The authors did not describe the methods for gathering the articles and the search terms used to conduct the review.

Description of Actual Data Sample:

The data sample included 10 studies that assessed the effects of antioxidants on cardiovascular events and had the following characteristics:

2 descriptive studies

Verlangieri et al. was conducted in the Unites States.
Gey and Puska studied 16 European regions.

2 case control studies

Riemersma et al. studied 110 agina subjects and 394 normal subjects.
Ramirez and Flowers studied 101 patients with angiographically proved coronary artery disease and 49 normal subjects.

4 prospective studies

Nurses' Health Study had 87,245 U.S. female nurses.
Health Professionals Follow-Up Study had 39, 910 U.S. male health professionals.
NHANES Study had 11,349 U.S. men and women.
Losonczy et al. was conducted with 11,178 elderly U.S. citizens.

2 randomized, double-blind, placebo-controlled studies

Alpha-Tocopherol Carotene Cancer Prevention Study (ATBC) included 29,133 Finnish male smokers.
Physicians' Health Study's subjects were 22,071 U.S. male physicians.
Cambridge Heart Antioxidant Study (CHAOS) used 2,002 British subjects with angiographically proved coronary artery disease.

Summary of Results:

Descriptive studies

Verlangieri et al. found an inverse association between fruit and vegetable intake and mortality from cardiovascular events.
Gey and Puska found an inverse association between α-tocopherol and death from cardiovascular events.

Case control studies

Riemersma et al. found lower plasma α-tocopherol in subjects with angina than in normal subjects.
Ramirez and Flowers found lower leukocyte ascorbic acid in subjects with CAD (coronary artery disease) than in normal subjects.

Prospective studies

The Nurses' Health Study found an inverse association between α-tocopherol intake and CAD events.
The Health Professionals Follow-Up Study showed the same results as the above study only in smokers and an inverse association between β-carotene intake and CAD.
NHANES Study reported an inverse association between ascorbic acid intake and death from cardiovascular events.
Losonczy et al. showed less CAD events in subjects who were on α-tocopherol than those who were not.

Randomized, double-blind, placebo controlled studies

Alpha-Tocopherol Carotene Cancer Prevention Study (ATBC) found no relationship between α-tocopherol or β-carotene on CAD events.
Physicians' Health Study found no effect of β-carotene on CAD events.
Cambridge Heart Antioxidant Study (CHAOS) showed a reduction of 77% for nonfatal myocardial infarction in subjects taking Vitamin E as compared to the placebo group.

Author Conclusion:

The following are concluded to be mechanisms of antioxidants:

Antioxidants may play a role in the modification of plaque stability, vasomotor function, and thrombosis.
Specific antioxidants may inhibit monocyte adhesion, protect against cytotoxic effects of oxidized LDL, and inhibit platelet aggregation.
Cellular antioxidants may preserve endothelium-derived nitric oxide activity and protect against endothelial dysfunction.

Funding Source:

Government:

National Institutes of Health

Industry:

Council for Tobacco Research - USA

Commodity Group:

Not-for-profit

American Heart Association

Other non-profit:

Reviewer Comments:

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?	Yes
	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?	Yes
	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?	Yes
	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?	Yes