According to a new study, patients with Alzheimer’s disease or mild cognitive impairment have lower blood vitamin E concentrations than people with normal cognitive functioning. Measuring vitamin E levels may therefore be of use when classifying and predicting the diagnosis of Alzheimer’s.
The study assessed cognitive functioning and plasma vitamin E concentrations and used different measure-ments from the high-resolution magnetic resonance (MRI) images of 253 individuals with an average age of 75 years (1). Among the participants, 81 individuals had been diagnosed with Alzheimer’s disease (AD), 86 with mild cognitive impairment (MCI), and 86 were deemed healthy. The study results showed that both AD and MCI patients had lower blood vitamin E levels compared to healthy participants. In addition, a combina-tion of structural MRI measurements and measurements of the plasma concentrations of all forms of vita-
min E (four tocopherols and four tocotrienols) was successfully used to distinguish participants with differing cognitive abilities.
The researchers commented that the study results support earlier findings suggesting that vitamin E may prevent cognitive dysfunction. Vitamin E is thought to protect cells from oxidative damage and is essential for normal immune and neurological functioning. Thus, sufficient vitamin E intakes may be particularly relevant for older individuals who are at risk of cognitive decline. However, in the US, for example, the average daily vitamin E intakes for men and women aged 70 years and over are 8.2 mg and 6.3 mg respectively, which are significantly below the Recommended Dietary Allowance (RDA) of 15 mg (2). The RDA is based on alpha-tocopherol, the most abundant form of vitamin E in the human body (3).
The other naturally occurring forms of vitamin E have been shown to play no role in meeting the vitamin E requirement because, although absorbed, they are rapidly metabolized and are present at much lower concentrations. While alpha-tocopherol has been the most frequently-studied form of vitamin E, the other forms are now receiving increased attention. After alpha-tocopherol, gamma-tocopherol, the predominant form of vitamin E in the US diet, has received the most attention; its role and the function of other forms of vitamin E have yet to be explored fully.
An earlier large prospective cohort study found that higher dietary intakes of vitamins E and C were associated with a lowered risk of dementia and Alzheimer’s disease (4). A follow-up study found that, compared with participants with the lowest vitamin E intake, those with the highest intake were 25% less likely to develop dementia in the long-term (5). Furthermore, some clinical trials have pointed towards potential benefits of increased alpha-tocopherol intakes (400 IU/day) for cardiovascular health in patients with elevated oxidative stress such as Type 2 diabetics (6). Other studies have either shown no cardio-vascular health benefits or suggested that the long-term use of very high doses of vitamin E (2,000 IU/day) may even increase mortality (7). The US Food and Nutrition Board has set the upper limit of tolerable intakes at 1000 mg vitamin E per day (1100 IU synthetic or 1500 IU natural vitamin E) for adults.