Does Beta-Carotene Preserve Memory?

Nov. 12, 2007 -- Beta-carotene supplements, when taken for many years, may preserve memory and other thinking skills, perhaps reducing the risk of dementia, according to a new study.

But even the study researchers recommend caution in interpreting the results, emphasizing that the improvement from the supplements was modest for the participants.

"Long-term beta-carotene had the effect of delaying changes in their memory by about a year," says Francine Grodstein, ScD, associate professor of medicine at Harvard Medical School and associate epidemiologist at Brigham & Women's Hospital in Boston, who led the study.

Other experts familiar with the new research say the study is no reason to begin taking supplements of beta-carotene simply to avoid dementia.

The antioxidant is also found in red, orange, and yellow fruits and vegetables, including sweet potatoes, mangoes, and cantaloupe.

Beta-Carotene and Memory

Long-term oxidative stress caused by "free radical" compounds circulating in the blood is thought to be a major factor in many health problems, including a decline in cognitive functioning. Decreased cognitive functioning, in turn, is thought to strongly predict the development of dementia.

So researchers are focusing on beta-carotene and other antioxidants, trying to find out if high intake or high blood levels can prevent the oxidative stress. Findings so far have been mixed. 

In the study, Grodstein and her co-researchers evaluated the effects of beta-carotene or placebo on cognitive abilities in nearly 6,000 men, including those who participated long term and short term.

The long-term group included 4,052 men who had been taking either 50 milligrams of beta-carotene or a placebo tablet every other day from 1982 to 1995 as participants in the Physicians' Health Study. The study was originally designed to look at the effect of beta-carotene, aspirin, and placebo on heart disease and cancer, and when the beta-carotene arm ended in 1995, researchers had found no effect on either disease from beta-carotene.

Some of the participants agreed to join the sequel study, Physicians' Health Study II, beginning in 1997, and kept their original assignments to take either beta-carotene or placebo.

An additional 1,904 men, new recruits, were assigned to take either the supplement or placebo, joining between 1998 and 2001.

The men were all in good health when they started the studies. Those who had taken part in the original study were about age 73 when the sequel study began; the new recruits were about 56 on average.

The men were followed up through 2003, completing yearly questionnaires about their health and their compliance with taking the pills. Their cognitive functioning was tested by telephone at least once between 1998 and 2002.

"The focus was on verbal memory," Grodstein tells WebMD. For instance, researchers would read a list of words and ask the participants to read them back immediately and again 20 minutes later.