CHICAGO, ILLINOIS. There is growing evidence that oxidative stress is a major factor in the development of Alzheimer's disease (AD). It is believed that accumulated damage to DNA and lipid membranes arising from attacks by free radicals and reactive oxygen species disrupt the normal functioning of cells and leads to neuronal death. Dietary antioxidants such as vitamin C, vitamin E and beta-carotene are highly effective in preventing oxidative stress and might thus help protect against the development of AD.
A team of American researchers has just released the results of a study aimed at determining whether older people with a high intake of dietary antioxidants are less likely to develop AD than are people with a lower intake. The study involved 815 people aged 65 years or older who were deemed to be free of AD when they entered the study. After an average follow-up of 3.9 years 131 of the participants had developed AD as ascertained through a 2.5-hour evaluation by a neurologist and support staff. The participants' intake of vitamin C, vitamin E and beta-carotene was determined via a food frequency questionnaire completed 1.7 years after baseline or about 2.3 years before the evaluation for AD.
The researchers found that participants with a high intake of vitamin E from food had a 67 per cent lower risk
of developing AD than did people with a low intake. This correlation only held true in participants who were
negative for the APOE epsilon4 allele (a known genetic risk factor for AD). Higher intakes of vitamin C and
beta-carotene had no statistically significant effect on the risk of AD and there was no indication that
supplementing with antioxidant vitamins, including vitamin E, was associated with a reduced risk. There
was, however, a trend for vitamin E (both from food and supplements) to prevent a decline in cognitive
function over the study period.