Eating food rich in vitamin E may reduce the risk of developing dementia, while insufficient levels of vitamin D may increase the risk of cognitive decline, say two new studies.
Archives of Neurology 67(7):819-825, 2010
Archives of Internal Medicine 170(13):1135-1141, 2010
People who consumed the highest average intakes of vitamin E from the diet were 25% less likely to develop dementia than people with the lowest average intakes, according to new data published in the Archives of Neurology.
Scientists from the Erasmus Medical Center in Rotterdam, the Netherlands, postulated that the benefits were related to the antioxidant activity of vitamin E, which counters the oxidative stress induced by a buildup of beta-amyloid protein.
The buildup of plaque from beta-amyloid deposits is associated with an increase in brain cell damage and death from oxidative stress. This is related to a loss of cognitive function and an increased risk of Alzheimer’s, the most common form of dementia that currently affects over 13 million people worldwide.
In another study from a Swedish study, published in the Journal of Alzheimer’s Disease, which found that a combination of different vitamin E forms could help prevent cognitive deterioration in advanced age.
There are eight forms of vitamin E: Four tocopherols (alpha, beta, gamma, delta) and four tocotrienols (alpha, beta, gamma, delta). Alpha-tocopherol (alpha-Toc) is the main source found in supplements and in the European diet, while gamma-tocopherol (gamma-Toc) is the most common form in the American diet.
Tocotrienols are only minor components in plants, although several sources with relatively high levels include palm oil, cereal grains and rice bran.
For the new study, the Rotterdam-based scientists analyzed data on the intakes of antioxidants—vitamins C and E, beta-carotene and flavonoids—in 5,395 people aged 55 and older. Questionnaires and meal-based checklists were used to establish intakes of these micronutrients.
The participants were followed for about 10 years, during which 465 people developed dementia, of which 365 cases were for Alzheimer’s disease.
After crunching the numbers, the researchers calculated that people with an average intake of 18.5 mg of vitamin E per day were 25% less likely to develop dementia than the people with an average of 9 mg per day. On the other hand, no associations were observed for dietary intake levels of vitamin C, beta-carotene and flavonoids.
“The brain is a site of high metabolic activity, which makes it vulnerable to oxidative damage, and slow accumulation of such damage over a lifetime may contribute to the development of dementia,” wrote the authors.
“In particular, when beta-amyloid (a hallmark of pathologic Alzheimer’s disease) accumulates in the brain, an inflammatory response is likely evoked that produces nitric oxide radicals and downstream neurodegenerative effects. Vitamin E is a powerful fat-soluble antioxidant that may help to inhibit the pathogenesis of dementia.”
The current issue of the Archives of Internal Medicine also carries new data from British researchers who report that seniors with low levels of vitamin D may be at an increased risk of cognitive decline.
Our cognitive performance declines naturally as we age, but new data from David Llewellyn and his colleagues at the University of Exeter in England indicates that insufficient levels of vitamin D may accelerate this decline.
The Exeter-based scientists analyzed vitamin D levels from blood samples of 858 adults aged 65 and older. Cognitive tests were undertaken at the start of the study, and again after three and six years.
The data showed that severe vitamin D deficiency, defined as blood levels of 25-hydroxyvitamin D (25(OH)D) of less than 25 nanomoles per liter—were associated with a 60% increase in the risk of substantial cognitive decline.
“If future prospective studies and randomized controlled trials confirm that vitamin D deficiency is causally related to cognitive decline, then this would open up important new possibilities for treatment and prevention,” concluded Llewellyn and his co-workers.