There is evidence that free radicals may contribute to the processes of cognitive impairment and so there has been considerable interest in recent years in whether vitamin E with its potential to protect against the damaging effects of free radicals might be useful in the treatment of mild cognitive impairment (MCI) and Alzheimer’s dementia (AD). The Cochrane Dementia and Cognitive Improvement Group has updated its review exploring this approach, which now includes two randomized trials involving people with AD and one with people with MCI, comparing vitamin E with placebo.
What did they find?
No or little benefit from using vitamin E to treat AD or MCI
How good is the evidence?
Data from the studies could not be combined as the two AD studies had different outcome measures: performance-based tasks in one and reaching certain end points (such as institutionalisation or loss of activities of daily living) in the other. The MCI study needed to be evaluated separately as it involved people with one particular type of MCI
The methods used were not always fully reported
One study had high drop-out rates and did not give reasons for this
The reviewers make some important points. They highlight that other research has shown that vitamin E, especially in the large doses used in treatment studies, may be associated with potentially serious side effects. Taken alongside the lack of evidence for its effectiveness, they recommend that vitamin E should not be used for the treatment of Alzheimer’s dementia and mild cognitive impairment. They also recommend that future trials should not be restricted to the alpha-tocopherol form of vitamin E and should consider assessing oxidant-antioxidant balance to determine whether the vitamin E treatment is having the desired effects.
Farina N, Isaac MGEKN, Clark AR, Rusted J, Tabet N. Vitamin E for Alzheimer’s dementia and mild cognitive impairment. Cochrane Database of Systematic Reviews 2012, Issue 11. Art. No.: CD002854. DOI: 10.1002/14651858.CD002854.pub3. http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD002854.pub3/abstract;