Beta carotene is thought to help fight cellular damage from oxidative stress, which is a major factor in cognitive decline. Although, there was evidence that an antioxidant, like beta carotene, might help preserve cognition previous studies have been inconclusive.
The study began in 1982 with 4,052 men, who had been randomly assigned to take either a placebo or 50 milligrams of beta carotene–roughly equivalent to five large carrots–on alternating days. Between 1998 and 2001, an additional 1,904 men were randomly assigned to one of the two groups. Both groups were followed through to 2003, completing yearly follow-up questionnaires with information about their health and their compliance with taking the pills.
The long-term participants stayed in the study for an average of 18 years and the short-term participants for an average of one year.
Results of the study showed that the men in the short-term group displayed no differences in cognition regardless of whether they took beta carotene or the placebo. However, men in the long-term group who took beta carotene had significantly higher scores on most of the cognitive tests.
Beta carotene does not come without risks. One known risk is the increased risk of lung cancer in smokers. However, its benefits for memory surpassed other medications tested in healthy older people.
There is no reason to believe that beta carotene supplementation does not carry the same benefit for women as it does for men, though that has yet to be tested. The research supports the possibility of successful interventions at the early stages of brain aging in healthy adults.