13/11/2007 - Men taking beta-carotene supplements for 15 years or more may experience a slower rate of age-related cognitive decline, according to a new study from Harvard.The study highlights the benefits of long-term nutritional support, noting that no short-term benefits were observed in the 1,904 men taking the supplements for less than ten years. "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," wrote the authors in the Archives of Internal Medicine.However, in an accompanying editorial in the same journal, Kristine Yaffe from the University of California, San Francisco cautioned that some issues were to be found in interpretation of the data since the study "had a complex design". Francine Grodstein and co-workers from Brigham and Women's Hospital and Harvard Medical School, Boston, tested the cognitive function of participants in the Physicians' Health Study II (PHSII), a continuation of the Physicians' Health Study (PHS) trial looking at the effects of beta carotene and other vitamin supplements on chronic disease, versus placebo.The subjects included participants from the original PHS (started in 1982) and newer recruits from 1998. Beta-carotene supplementation was 50 mg on alternate days.The researchers tested the general cognition, verbal memory, and category fluency of 5956 participants, including 4052 participants from the PHS with a minimum supplementation period of 18 years.The long-term beta-carotene supplementation was associated with a significantly higher mean global score, compared to placebo. This group also performed significantly better than placebo for verbal memory.On the other hand, men in the short-term group displayed no differences in cognition regardless of whether they took beta carotene or placebo.The potential mechanism for the protective effects was postulated to be related to the role of vitamin A (beta-carotene is converted to vitamin A in the body) on beta-amyloid protein production. The build-up of plaque from beta-amyloid deposits is associated with an increase in brain cell damage and death from oxidative stress. This is related to a loss of cognitive function and an increased risk of Alzheimer's.The study is the first to look at long-term antioxidant supplementation in relation to a decline in cognitive function that occurs with naturally with age, and that precedes diseases such as Alzheimer's.
