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.
"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.
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 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.
According to the new trial, the benefits of long-term supplementation in a healthy population are encouraging. "Thus, the public health value of beta carotene supplementation merits careful evaluation," concluded the authors. "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."
In the editorial, another researcher stated: "The authors suggest that long-term exposure to antioxidants may be needed to have an effect on the underlying pathologic processes linked to changes in cognition.
"This is certainly plausible, given that the neuropathologic changes underlying clinically significant cognitive impairment appear to take years, if not decades. Thus, neuroprotection may have the greatest benefit early on in the process.
Bonnie - have we not said all along that with studies done on nutrients such as beta carotene, you need to look at long-term prevention in healthy subjects? Well, here it is, finally! The structure and length were ideal. The dose was adequate. Most importantly, Alzheimer's and dementia, as with many chronic, degenerative diseases, slowly create a decline in mental function over time. It is perfectly logical to deduce that an antioxidant taken over a long period of time would have a positive cumulative effect. The antioxidant is fighting daily to protect neurological function against the rigors of everyday life. The researchers postulate the the protective affect could delay the onset of severe symptoms for up to 18 months. Taking into account a slower degradation over time, a little beta carotene can greatly enhance quality of life.