In animals, PS has been shown to attenuate many neuronal effects of aging, and to restore normal memory on a variety of tasks. Preliminary findings with humans, though, are limited. For older adults with probable
Alzheimer's disease, a single study failed to demonstrate positive effects of PS on memory performance. For older adults with moderate
cognitive impairment, PS has produced consistently modest increases in recall of word lists. Positive effects have not been as consistently reported for other memory tests. There is one report of consistent benefits across a number of memory tests for a subset of normal adults who performed more poorly than their peers at baseline. The
choline compounds PC and
citicoline are thought to promote synthesis and transmission of
neurotransmitters important to memory. PC has not proven effective for improving memory in patients with probable
Alzheimer's disease. The issue remains open for older adults without serious degenerative neural disease. Research on
citicoline is practically nonexistent, but one study reported a robust improvement in story recall for a small sample of normally aging older adults who scored lower than their peers in baseline testing. Animal studies suggest that
piracetam may improve neuronal efficiency, facilitate activity in
neurotransmitter systems, and combat the age-related decrease in receptors on the neuronal membrane. However, for patients with probable
Alzheimer's disease, as well as for adults with age-associated memory impairment, there is no clear-cut support for a mnemonic benefit of
piracetam.
Vinpocetine increases blood circulation and metabolism in the brain. Animal studies have shown that
vinpocetine can reduce the loss of neurons due to decreased blood flow. In three studies of older adults with memory problems associated with poor brain circulation or
dementia-related disease,
vinpocetine produced significantly more improvement than a placebo in performance on global cognitive tests reflecting attention, concentration, and memory. Effects on episodic memory per se have been tested minimally, if at all. ALC participates in cellular energy production, a process especially important in neurons, and in removal of toxic accumulation of
fatty acids. Animal studies show that ALC reverses the age-related decline in the number of neuron membrane receptors. Studies of patients with probable
Alzheimer's disease have reported nominal advantages over a range of memory tests for ALC-treated patients relative to placebo groups. Significant differences have been reported rarely, however. Whether ALC would have mnemonic benefits for aging adults without
brain disease is untested as far as we know.
Antioxidants help neutralize tissue-damaging
free radicals, which become more prevalent as organisms age. It is hypothesized that increasing
antioxidant levels in the organism might retard or reverse the damaging effects of
free radicals on neurons. Thus far, however, studies have found that
vitamin E does not significantly slow down memory decline for Alzheimer's patients and does not produce significant memory benefits among early Parkinson's patients. Neither did a combination of
vitamins E and C significantly improve college students' performance on several cognitive tasks.
CONCLUSIONS: