There are plenty of them out there: Ginkgo, Vinpocetine, Huperzine A, Phosphatidylserine (PS) DHA, and claims of antioxidants and B vitamins to keep you mentally sharp. As of yet, there are no published studies behind any of the claims. Think about it. We would all be geniuses, and Alzheimer's would be a thing of the past.
According to studies at the University of Iowa, taking a walk everyday improves memory better than Omega 3 (DHA) supplements. Several studies have concluded that there is no evidence that PS has any effect on cognitive function. B6, B12, and Folic acid have proven to show little, if any improvement in several studies. However, large doses of the B vitamins may spur the growth of precancerous colorectal polyps. The National Library of Medicine has no known studies linking huperazine A and improved memory; no verifiable evidence can be found. Consumerlab.com (a consumer website that tests supplements) points out that huperzine A is very expensive, which is an incentive for manufacturers to use less than the actual amount the labels claim. One brand analyzed was consistently deficient by 15% of the amount listed. This practice is not uncommon in many OTC supplements and herbal remedies.
As for the claim for antioxidants preventing oxidative damage to brain cells, several large randomized trials at Brigham and Women's Hospital have come up with no evidence that they improve memory. Long term studies continue, as it may be possible however, that a lifetime of good eating habits are important for memory.
Bottom line: Don't expect a pill to fix a lifetime of poor eating habits, shed pounds, turn back the clock, or cure the common cold. By the time people realize they don't work, the manufacturers have already made their millions and are concocting their next marketing scheme.
~American Journal of Clinical Nutrition, 2011