Long-Term Beta Carotene Use May Protect Against Dementia

Long-Term Beta Carotene Use May Protect Against Dementia
MONDAY, Nov. 12 (HealthDay News) -- Taking supplements of theantioxidant beta carotene for a long time -- 15 years or more -- appearsto lessen the decline in thinking ability that comes with Alzheimer'sdisease, a study finds.
"My hypothesis is that it's how long you take it," said study leadauthor Francine Grodstein, an associate professor of medicine at HarvardMedical School and a researcher at Brigham and Women's Hospital inBoston.
The idea that antioxidants such as beta carotene can help protectagainst Alzheimer's disease is not new. But the idea remainscontroversial, because a number of studies have not produced positiveresults. This latest trial, which started as the Physicians Health StudyII, stretches back to 1982.
That year, 4,052 men were assigned to take daily doses of either 50milligrams of beta carotene -- the amount in about five large carrots --or a placebo every other day. An additional 1,904 men were randomlyassigned to one of the two groups between 1998 and 2001.
All the men filled out yearly questionnaires about their health andcompliance with the regimen, and all had telephone assessments of theirthinking ability at least once between 1998 and 2002.
A difference emerged between long-term and short-term participants. Themen who had stayed in the trial for an average of 18 years scoredsignificantly higher on most of the tests of cognitive ability. "Theirmemory was equivalent to that of men about a year younger," Grodsteinsaid.
What works for men almost certainly should work for women, she said,and the idea that long-term use of an intervention is important should beapplied to other preventive measures against Alzheimer's disease.
"Our research supports the possibility of successful interventions atearly stages of brain aging in healthy adults," Grodstein said.
But beta carotene is not entirely risk-free, she noted. "In studies ofmale smokers, beta carotene supplements increase the lung cancer mortalityrate," Grodstein said.
The findings are published in the Nov. 12 issue of Archives ofInternal Medicine.
An accompanying editorial in the journal by Dr. Kristine Yaffe,professor of psychiatry, neurology, epidemiology and biostatistics at theUniversity of California, San Francisco, circled warily around the conceptof long-term antioxidant supplements. One possibility, Yaffe said, is thatsomeone who remembers to take a supplement for 18 years is in bettermental shape to begin with than someone who doesn't. (Grodstein said thatcompliance had been checked as carefully for the men taking theplacebo.)
The idea that long-term use of the supplements is necessary "iscertainly plausible, given that the neuropathologic changes underlyingclinically significant impairment appear to take years, if not decades,"Yaffe wrote. But evidence for that concept would be difficult to obtain,since it would require trials lasting 25 to 30 years, she said.
"For the clinician, there is no convincing justification to recommendthe use of antioxidant dietary supplements to maintain cognitiveperformance in cognitively normal adults or those with mild cognitiveimpairment," Yaffe concluded.
The Alzheimer' Association makes no recommendation about antioxidantsupplements. Both the American Heart Association and the American CancerSociety say the evidence for supplements is inconclusive and recommend adiet rich in fruits and vegetables.