Green tea is widely drunk in many cultures, especially in Asia, and is known to have potent health benefits. These benefits are attributed to its polyphenol content (particularly the flavanols and flavonols). In cell cultures and animal studies, the polyphenols have been proven to prevent neurotoxin-induced cell injury. Green tea also has anti-inflammatory properties and, according to a study performed on aged mice, may delay memory regression. It’s safe to drink several cups of green tea per day, though it may be more efficacious to take a green tea extract supplement to reach a daily dose of 400 to 500 mg of EGCG, one of the main active components of green tea.
It is at the top of the supplement snake oil list thanks to tons of correlations; for a review, see Luchtman & Song 2013 but some specifics include Teenage Boys Who Eat Fish At Least Once A Week Achieve Higher Intelligence Scores, anti-inflammatory properties (see Fish Oil: What the Prescriber Needs to Know on arthritis), and others - Fish oil can head off first psychotic episodes (study; Seth Roberts commentary), Fish Oil May Fight Breast Cancer, Fatty Fish May Cut Prostate Cancer Risk & Walnuts slow prostate cancer, Benefits of omega-3 fatty acids tally up, Serum Phospholipid Docosahexaenonic Acid Is Associated with Cognitive Functioning during Middle Adulthood endless anecdotes.
Barbara Sahakian, a neuroscientist at Cambridge University, doesn’t dismiss the possibility of nootropics to enhance cognitive function in healthy people. She would like to see society think about what might be considered acceptable use and where it draws the line – for example, young people whose brains are still developing. But she also points out a big problem: long-term safety studies in healthy people have never been done. Most efficacy studies have only been short-term. “Proving safety and efficacy is needed,” she says.
A picture is worth a thousand words, particularly in this case where there seems to be temporal effects, different trends for the conditions, and general confusion. So, I drag up 2.5 years of MP data (for context), plot all the data, color by magnesium/non-magnesium, and fit different LOESS lines to each as a sort of smoothed average (since categorical data is hard to interpret as a bunch of dots), which yields:
70 pairs is 140 blocks; we can drop to 36 pairs or 72 blocks if we accept a power of 0.5/50% chance of reaching significance. (Or we could economize by hoping that the effect size is not 3.5 but maybe twice the pessimistic guess; a d=0.5 at 50% power requires only 12 pairs of 24 blocks.) 70 pairs of blocks of 2 weeks, with 2 pills a day requires (70 \times 2) \times (2 \times 7) \times 2 = 3920 pills. I don’t even have that many empty pills! I have <500; 500 would supply 250 days, which would yield 18 2-week blocks which could give 9 pairs. 9 pairs would give me a power of:
Clinical psychiatrist Emily Deans has a private practice in Massachusetts and teaches at Harvard Medical School. She told me by phone that, in principle, there's "probably nothing dangerous" about the occasional course of nootropics for a hunting trip, finals week, or some big project. Beyond that, she suggests considering that it's possible to build up a tolerance to many neuroactive products if you use them often enough.
According to Dr. Lisa, "neuro-nutrition is how our internal work translates to the external, for instance how we perform, behave, and use our strength, as opposed to 'dieting' which has an external (aesthetic) goal." An important portion of her research and theories on this matter root from her Mediterranean upbringing. She recalls immediately noticing how drastically different was the Western's culture in regards to food upon her arrival to the U.S. Interestingly enough, a recent study published in the British Medical Journal showed just how stark the difference between these lifestyles are and concluded that the Western lifestyle usually leads to "accelerated aging and increased risk of future dementia." 
Racetams, such as piracetam, oxiracetam, and aniracetam, which are often marketed as cognitive enhancers and sold over-the-counter. Racetams are often referred to as nootropics, but this property is not well established.[31] The racetams have poorly understood mechanisms, although piracetam and aniracetam are known to act as positive allosteric modulators of AMPA receptors and appear to modulate cholinergic systems.[32]