Antioxidant Vitamins May Reduce Risk of Alzheimer’s Disease
Approximately 5% of the US population between the ages of 65 and 74 have ]]>Alzheimer’s disease (AD)]]> , and nearly half of those age 85 and older may have the disease. The early symptoms of AD include forgetfulness and loss of concentration, which are often dismissed as natural signs of aging. As the disease progresses, people with AD develop other symptoms, including memory loss, language deterioration, impaired ability to process visual information, poor judgment, confusion, restlessness, and mood swings. Eventually AD destroys cognition, personality, and the ability to function. Younger people may also develop AD, but it is much less common.
Unfortunately, the cause of AD is unknown and there is no cure. However, researchers do know that the neurons (brain cells) of patients who have AD are damaged. They also know that neurons are particularly sensitive to damage by free radicals, a byproduct of normal cellular metabolism. Free radicals are hazardous because they are molecularly unstable and must steal electrons from other molecules in the cell in order to become stable. Unfortunately, this electron theft can damage both proteins and cellular DNA.
To guard against the harm caused by unchecked free radicals, our cells have developed ways to absorb at least some of them before they have a chance to wreak their full havoc. Antioxidants, for example, are capable of neutralizing the damaging effects of free radicals. Certain foods, most notably fresh fruits and vegetables, are rich in these antioxidants, which go by names like ]]>vitamin E]]> , ]]>vitamin C]]> and ]]>beta-carotene]]> . These same antioxidants, of course, are available as dietary supplements in the form of pills and other over-the-counter products.
Recently, a group of researchers set out to see if antioxidant supplement use could help reduce the risk of developing AD. The results of their study were published in the January issue of the Archives of Neurology. The researchers found that the use of vitamin E and vitamin C supplements, particularly in combination, was associated with a reduced risk of AD.
About the study
Between 1995 and 1997, the researchers assessed 4740 study participants, all age 65 or older for the presence of dementia and AD. Their use of supplements was also determined at this time. The participants were reassessed between 1998 and 2000.
The participants were divided into one of several categories:
- Vitamin E users (those who either took a vitamin E supplement or a multivitamin containing more than 400 international units (IU) of vitamin E)
- Vitamin C users (those who took either a vitamin C supplement or a multivitamin containing more than 500 milligrams (mg) of ascorbic acid)
- Multivitamin users (those who took a multivitamin that contained doses of vitamin E lower than 400 IU and doses of vitamin C lower than 500 mg)
- Vitamin B-complex users (those who took a vitamin B supplement containing a complex of multi-B vitamins)
The researchers found that the use of vitamin E and vitamin C supplements in combination was associated with a reduction in the prevalence and incidence of AD by 78% and 64% respectively. Study participants who took vitamin E supplements in combination with multivitamins containing vitamin C, also saw a risk reduction, but to a lesser degree. This was not the case among those who used either vitamin E or vitamin C supplements alone, used only multivitamins, or who used vitamin B-complex supplements.
How does this affect you?
The researchers concluded that the use of vitamin E and C supplements in combination is associated with reduced prevalence and incidence of AD.
One reason posed for the lack of protection for those taking multivitamins is that the current recommended daily dose of vitamin E is 22 IU. The current recommended daily dose of vitamin C is between 75 and 90 mg. These amounts are considerably less than the 1000 IU available in most vitamin E supplements and the 500 to 1000 mg available in most vitamin C supplements. Even eating a healthful diet would not provide these vitamins at such high doses.
A drawback of this kind of study is that the researchers did not randomly assign antioxidant supplements to elderly subjects and then follow them over time to see who developed AD and who did not. This would avoid a number of biases that often creep into less rigorous study designs like the one reported here. Nevertheless, vitamins E and C are safe at these doses, and many older adults do not get adequate amounts of these and other nutrients in their regular diets.
While this study in no way suggests that deficiencies of dietary antioxidants actually cause AD, it does suggest that a person who is predisposed to AD may be able to delay its onset by supplementing their diet with these vitamins. Until more definitive studies are conducted, it may be that remembering to take your E’s and C’s may help you keep your memory a little longer.
Alzheimer's Disease Education & Referral Center (ADEAR)
National Institute of Neurological Disorders and Stroke
Alzheimer’s disease fact sheet. Alzheimer's Disease Education & Referral Center (ADEAR). Available at: http://www.alzheimers.org/pubs/adfact.html . Accessed January 22, 2004.
NINDS Alzheimer's Disease Information Page. National Institute of Neurological Disorders and Stroke. Available at: http://www.ninds.nih.gov/health_and_medical/disorders/alzheimersdisease_doc.htm . Accessed January 22, 2004.
Zandi PP, Anthony JC, Khachaturian AS, et al. Reduced risk of Alzheimer’s disease in users of antioxidant vitamin supplements. The Cache County Study. Arch Neurol. 2004;61:82-88.
Last reviewed Jan 23, 2004 by ]]>Richard Glickman-Simon, MD]]>
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