Huperzine A: This compound is found in a firmoss plant called Huperzia serrata.  Studies conducted on Huperzine A so far have not used the best methodology, so scientists are still not sure how beneficial this compound is for preventing or treating Alzheimer’s disease.  But one review of studies on Huperzine A concluded that the compound “appears to have beneficial effects on improvement of cognitive function, daily living activity, and global clinical assessment in participants with Alzheimer’s disease.”
Vinpocetine: This chemical is a semi-synthetic derivative of an extract from periwinkle.  It acts as a potent anti-inflammatory agent, and has also received some testing as a supplement for memory enhancement.  While research results are inconclusive right now, this chemical has been shown to increase blood circulation and metabolism in the brain and may slow down neuron loss.  Some tests have also shown that it can improve concentration and attention.
In this large population-based cohort, we saw consistent robust associations between cola consumption and low BMD in women. The consistency of pattern across cola types and after adjustment for potential confounding variables, including calcium intake, supports the likelihood that this is not due to displacement of milk or other healthy beverages in the diet. The major differences between cola and other carbonated beverages are caffeine, phosphoric acid, and cola extract. Although caffeine likely contributes to lower BMD, the result also observed for decaffeinated cola, the lack of difference in total caffeine intake across cola intake groups, and the lack of attenuation after adjustment for caffeine content suggest that caffeine does not explain these results. A deleterious effect of phosphoric acid has been proposed (26). Cola beverages contain phosphoric acid, whereas other carbonated soft drinks (with some exceptions) do not.
Unlike many hypothetical scenarios that bioethicists worry about - human clones, "designer babies" - cognitive enhancement is already in full swing. But how much do they actually help? Are they potentially harmful or addictive? Then there's the question of what we mean by "smarter". Could enhancing one kind of thinking exact a toll on others? All these questions need proper scientific answers, but for now much of the discussion is taking place furtively, among the increasing number of people who are performing daily experiments on their own brains.
Some people aren’t satisfied with a single supplement—the most devoted self-improvers buy a variety of different compounds online and create their own custom regimens, which they call “stacks.” According to Kaleigh Rogers, writing in Vice last year, companies will now take their customers’ genetic data from 23andMe or another source and use it to recommend the right combinations of smart drugs to optimize each individual’s abilities. The problem with this practice is that there’s no evidence the practice works. (And remember, the FDA doesn’t regulate supplements.) Find out the 9 best foods to boost your brain health.
That study is also interesting for finding benefits to chronic piracetam+choline supplementation in the mice, which seems connected to a Russian study which reportedly found that piracetam (among other more obscure nootropics) increased secretion of BDNF in mice. See also Drug heuristics on a study involving choline supplementation in pregnant rats.↩
Mosconi clarifies a few concepts. Other authors have advanced that the brain needs fat, including saturated fat, and cholesterol to function properly. Not so, Mosconi indicates that the fats we eat (saturated fat from animal protein) and cholesterol can’t even cross the blood-brain barrier. The brain needs a completely different type of fat: essential Polyunsaturated Fatty Acids (PUFAs). They include Omega-3s and Omega-6s fatty acids. Good sources of Omega-3s include fish, oils, eggs.

The main concern with pharmaceutical drugs is adverse effects, which also apply to nootropics with undefined effects. Long-term safety evidence is typically unavailable for nootropics.[13] Racetams — piracetam and other compounds that are structurally related to piracetam — have few serious adverse effects and low toxicity, but there is little evidence that they enhance cognition in people having no cognitive impairments.[19]