Long story short, aging is your brain’s worst enemy. The same applies to all organs of our body, but the brain suffers the most. Both neurotransmitters and neurons are taking the blow too. As a result, the neuron communication is affected. Now, this may seem like the rocket science to you, but it’s enough to say, serotonin and dopamine are the most important neurotransmitters. Without these components, you can forget about good mood. Serotonin and dopamine levels drop at a rate of approximately 10% for every decade you add to your age.
Dr. Mosconi: I love apples. When I’m at the office though, I’ll bring homemade trail mix [made with] higher quality dried fruit, nuts and seeds. [It's] packed with brain-essential nutrients that come from goji berries, Brazil nuts, walnuts, cacao nibs, pistachios, hemp hearts and  more. Plus, I drink plenty of rose water throughout the day, which is very anti-inflammatory.
Microdosing With Psilocybin: Psilocybin, AKA “magic mushrooms”, are naturally occurring fungi, with over 180 different species and research from archaeologist evidence has shown that humans have been using psilocybin mushrooms for over 7,000 years. I’ve personally found microdoses of psilocybin, AKA “magic mushrooms”, to be best for nature immersions, hiking, journaling or self-discovery.  Psilocybin primarily interacts with the serotonin receptors in the brain and has been used in therapeutic settings to treat disorders such as headaches, anxiety, depression, addiction, and obsessive-compulsive disorders (See additional studies here, here, here and here). There is limited data to show any adverse drug interactions with the use of psilocybin, and liver function, blood sugar, and hormonal regulation all appear to be unaffected during consumption (although it is best to avoid alcohol and any serotonin-based antidepressants while taking any psychedelics) (See studies here, here and here). A microdose of psilocybin is generally between 0.2 grams and .5 grams, and I’d highly recommend you start on the low end of the dosage range with these or any of the psychedelics mentioned here.
One should note the serious caveats here: it is a small in vitro study of a single category of human cells with an effect size that is not clear on a protein which feeds into who-knows-what pathways. It is not a result in a whole organism on any clinically meaningful endpoint, even if we take it at face-value (many results never replicate). A look at followup work citing Rapuri et al 2007 is not encouraging: Google Scholar lists no human studies of any kind, much less high-quality studies like RCTs; just some rat followups on the calcium effect. This is not to say Rapuri et al 2007 is a bad study, just that it doesn’t bear the weight people are putting on it: if you enjoy caffeine, this is close to zero evidence that you should reduce or drop caffeine consumption; if you’re taking too much caffeine, you already have plenty of reasons to reduce; if you’re drinking lots of coffee, you already have plenty of reasons to switch to tea; etc.
Even the best of today’s nootropics only just barely scratch the surface. You might say that we are in the “Nokia 1100” phase of taking nootropics, and as better tools and more data come along, the leading thinkers in the space see a powerful future. For example, they are already beginning to look past biochemistry to the epigenome. Not only is the epigenome the code that runs much of your native biochemistry, we now know that experiences in life can be recorded in your epigenome and then passed onto future generations. There is every reason to believe that you are currently running epigenetic code that you inherited from your great-grandmother’s life experiences. And there is every reason to believe that the epigenome can be hacked – that the nootropics of the future can not only support and enhance our biochemistry, but can permanently change the epigenetic code that drives that biochemistry and that we pass onto our children.
(We already saw that too much iodine could poison both adults and children, and of course too little does not help much - iodine would seem to follow a U-curve like most supplements.) The listed doses at iherb.com often are ridiculously large: 10-50mg! These are doses that seems to actually be dangerous for long-term consumption, and I believe these are doses that are designed to completely suffocate the thyroid gland and prevent it from absorbing any more iodine - which is useful as a short-term radioactive fallout prophylactic, but quite useless from a supplementation standpoint. Fortunately, there are available doses at Fitzgerald 2012’s exact dose, which is roughly the daily RDA: 0.15mg. Even the contrarian materials seem to focus on a modest doubling or tripling of the existing RDA, so the range seems relatively narrow. I’m fairly confident I won’t overshoot if I go with 0.15-1mg, so let’s call this 90%.
Methylphenidate – a benzylpiperidine that had cognitive effects (e.g., working memory, episodic memory, and inhibitory control, aspects of attention, and planning latency) in healthy people.[21][22][23] It also may improve task saliency and performance on tedious tasks.[25] At above optimal doses, methylphenidate had off–target effects that decreased learning.[26]