A man who has been taking carotene supplements for at least 15 years is much less likely to suffer from cognitive decline than a man who never took the supplements, according to an article in Archives of Internal Medicine (JAMA/Archives), November 12th issue.

The authors explain that a decline in thinking, learning and memory skills (cognitive ability) is a strong predictor of dementia. Dementia is a rising public health issue. It is thought that ‘oxidative stress‘ is a key factor in cognitive decline. Studies have indicated that antioxidant supplements may help preserve one’s cognition – however, these studies have mostly been inconclusive, the authors write.

Francine Grodstein, Sc.D., Brigham and Women’s Hospital (BWH) and Harvard Medical School, Boston, and team looked at beta carotene (an antioxidant) data and what effect it might have on the cognitive abilities of two groups of males. A long term group included 4,052 men – these men had been randomly assigned to receive either 50 milligrams of beta carotene every other day or a placebo in 1982. From 1990 to 2001 1,904 more men were randomly placed into one of the two groups. All the men were monitored (followed-up) up to the end of 2004 – they filed in follow-up questionnaires which revealed data about their health and compliance with taking the pills. Through telephone conversations they were assessed for cognitive function during the period 1998-2002.

The long-term group received their beta carotene or placebo for 18 years (average) while the short-term group did so for one year (average).

The men in the beta carotene and placebo short-term groups revealed no difference in cognition. However, those in the long-term group did. Those in the long-term group who had been taking their beta carotene scored significantly higher than the long-term placebo group in numerous cognitive tests.

The researchers explained “In this generally healthy population, the extent of protection conferred by long-term treatment appeared modest; nonetheless, studies have established that very modest differences in cognition, especially verbal memory, predict substantial differences in eventual risk of dementia; thus, the public health impact of long-term beta carotene use could be large.”

Beta carotene does come with some undesirable side effects – smokers who take it have a further elevated risk of developing lung cancer, the researchers note. However, beta carotene offered superior cognitive benefits to any other drug tested on healthy older people.

The authors concluded “Thus, the public health value of beta carotene supplementation merits careful evaluation. Moreover, as these data support the possibility of successful interventions at early stages of brain aging in well-functioning subjects, investigations of additional agents that might also provide such neuroprotection should be initiated.”


Even though the results are credible, Kristin Yaffe, M.D., San Francisco VA Medical Center and University of California, San Francisco, USA, wrote that other possible explanations exist for beta carotene’s neuroprotective effects. It is possible the long-term takers of beta carotene in this study had certain characteristics that made them less prone to suffer cognitive deterioration.

Dr. Yaffe wrote “For the clinician, there is no convincing justification to recommend the use of antioxidant dietary supplements to maintain cognitive performance in cognitively normal adults or in those with mild cognitive impairment. Furthermore, there is new concern that high-dose antioxidant supplementation, including beta carotene, may have adverse health consequences including mortality.”

Dr. Yaffe says further studies are needed.

Article – Arch Intern Med. 2007;167(20):2184-2190
Editorial – Arch Intern Med. 2007;167(20):2167-2168

Written by׃ Christian Nordqvist