Taking these drugs without a doctor’s supervision can be dangerous. There are interactions and contraindications that can cause serious problems. These drugs should not be used if you drink alcohol or take an antidepressant. (50) The possibility of adverse drug reactions should not be taken lightly. By some calculations, adverse drug reactions are now the fourth leading cause of death in the US. (51)
Dr Hart explained how communication between the gut and the brain is controlled via our immune system, our endocrine system (hormones) and our central nervous system, which are all under the influence of the bacteria in our gut. The types and amount of these bacteria, known as our gut microbiome, can be directly impacted by factors such as diet, stress, pollution and medications (2) and the composition of the microbiome is also understood to affect one’s susceptibility to food sensitivities and intolerances (3).  
Certain B vitamins - B6, B12 and folic acid - are known to reduce levels of a compound called homocysteine in the blood. Elevated levels of homocysteine are associated with increased risk of stroke, cognitive impairment and Alzheimer's disease. A study of a group of elderly patients with mild cognitive impairment found that after two years of intervention with high doses of B6, B12 and folic acid there was significantly less brain shrinkage compared to a subset given placebo treatment. Opt for B-rich foods like eggs, chicken, fish and leafy greens.
10:30 AM; no major effect that I notice throughout the day - it’s neither good nor bad. This smells like placebo (and part of my mind is going how unlikely is it to get placebo 3 times in a row!, which is just the Gambler’s fallacy talking inasmuch as this is sampling with replacement). I give it 60% placebo; I check the next day right before taking, and it is. Man!
(As I was doing this, I reflected how modafinil is such a pure example of the money-time tradeoff. It’s not that you pay someone else to do something for you, which necessarily they will do in a way different from you; nor is it that you have exchanged money to free yourself of a burden of some future time-investment; nor have you paid money for a speculative return of time later in life like with many medical expenses or supplements. Rather, you have paid for 8 hours today of your own time.)

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.

Forums including reddit.com/r/Nootropics/ have more than 140,000 subscribers discussing products with names like Orange Brainwash and GodMode. Nootropics are blends of ingredients touted as a low-risk way to enhance learning, memory, motivation, and even serenity. These ingredients range from herbs such as water hyssop (Bacopa monnieri) and arctic root to chemicals such as vinpocetine.

The brain of animals features in French cuisine, in dishes such as cervelle de veau and tête de veau. A dish called maghaz is a popular Muslim cuisine in Pakistan, Bangladesh, parts of India, and diaspora countries. In Turkish cuisine brain can be fried, baked, or consumed as a salad. In Chinese cuisine, brain is a delicacy in Chongqing or Sichuan cuisine, and it is often cooked in spicy hot pot or barbecued. In the southern part of China, pig brain is used for "Tianma Zhunao Tang". In South India goat brain curry or fry is a delicacy.
Like everything else in your body, the brain cannot work without energy. The ability to concentrate and focus comes from an adequate, steady supply of energy - in the form of glucose in our blood to the brain. Achieve this by choosing wholegrains with a low-GI, which release glucose slowly into the bloodstream, keeping you mentally alert throughout the day. Opt for 'brown' wholegrain cereals, granary bread, rice and pasta.
As far as anxiety goes, psychiatrist Emily Deans has an overview of why the Kiecolt-Glaser et al 2011 study is nice; she also discusses why fish oil seems like a good idea from an evolutionary perspective. There was also a weaker earlier 2005 study also using healthy young people, which showed reduced anger/anxiety/depression plus slightly faster reactions. The anti-stress/anxiolytic may be related to the possible cardiovascular benefits (Carter et al 2013).
Choline is a nootropic: it enhances your ability to pay attention and learn efficiently,[18] probably because you use a lot of acetylcholine during mentally-demanding tasks, and choline helps you synthesize enough to work harder and go longer.[19] Choline also links to decreased brain inflammation in a dose-dependent manner — the more choline you eat, the less inflamed your brain tends to be.[20]

The body has its own inherent detoxification pathways that are responsible for packaging and removing heavy metals safely from the system. For example, glutathione is known as the body’s ‘master antioxidant’ and aside from playing an important role in preventing free radicals from causing damage to the body’s cells, it also helps to bind to heavy metals and remove them from the body. Research shows that glutathione levels are lower than normal in those on the autism spectrum, so enhancing levels through the diet may be an effective way to prevent the accumulation of heavy metals. Consuming sulfur-rich foods such as broccoli, cabbage, onions, garlic, kale and cauliflower can boost glutathione levels, as well as milk thistle, which has unique flavonoids that also support glutathione production.
Omega-3 fatty acids: DHA and EPA – two Cochrane Collaboration reviews on the use of supplemental omega-3 fatty acids for ADHD and learning disorders conclude that there is limited evidence of treatment benefits for either disorder.[42][43] Two other systematic reviews noted no cognition-enhancing effects in the general population or middle-aged and older adults.[44][45]