Systematic reviews and meta-analyses of clinical human research using low doses of certain central nervous system stimulants found enhanced cognition in healthy people.[21][22][23] In particular, the classes of stimulants that demonstrate cognition-enhancing effects in humans act as direct agonists or indirect agonists of dopamine receptor D1, adrenoceptor A2, or both types of receptor in the prefrontal cortex.[21][22][24][25] Relatively high doses of stimulants cause cognitive deficits.[24][25]
Eat a healthy diet.  While the best nootropic supplements can help fuel your brain, they cannot fill every gap in your diet.  If you want your brain to function at its best, a healthy, nutritious, varied diet is essential.  Make sure that you are eating fatty fish and foods fortified with DHA omega-3 fatty acids.  Get plenty of vitamin E and antioxidants like lutein.

I have lots of problems with procrastination and productivity, most likely due to a mild case of ADHD, and recently it's been getting worse and worse. I was a bit hesitant to take Addium at first because I, like most people, had heard about it as a tool for students to use for cramming and it's results sound a little bit like the results of taking Adderall recreationally, which isn't my cup of tea. I was also hesitant to try it because it's marketing just makes it seem like it's a scam pill, and I unfortunately take quality of advertising rather seriously. I changed my mind (after another particularly trying week at work) after a friend of mine actually recommended it for me and told me that she was having great results from it. In my mind, I figured that if a real person,someone I know and trust, tells me in real life that I should maybe try it...then I may as well give it a shot. I ordered the Addium and as soon as I got it, I started taking it immediately. The Addium actually works. I can't believe it. It's helped a lot with my productivity at work. I'm taking just one tablet per day and it seems to be doing the trick. I think the best part about it is that it's not something that you have to continuously take every day.
Googling, you sometimes see correlational studies like Intake of Flavonoid-Rich Wine, Tea, and Chocolate by Elderly Men and Women Is Associated with Better Cognitive Test Performance; in this one, the correlated performance increase from eating chocolate was generally fairly modest (say, <10%), and the maximum effects were at 10g/day of what was probably milk chocolate, which generally has 10-40% chocolate liquor in it, suggesting any experiment use 1-4g. More interesting is the blind RCT experiment Consumption of cocoa flavanols results in acute improvements in mood and cognitive performance during sustained mental effort11, which found improvements at ~1g; the most dramatic improvement of the 4 tasks (on the Threes correct) saw a difference of 2 to 6 at the end of the hour of testing, while several of the other tests converged by the end or saw the controls winning (Sevens correct). Crews et al 2008 found no cognitive benefit, and an fMRI experiment found the change in brain oxygen levels it wanted but no improvement to reaction times.
Dr. Lisa Mosconi, whose research spans an extraordinary range of specialties including brain science, the microbiome, and nutritional genomics, notes that the dietary needs of the brain are substantially different from those of the other organs, yet few of us have any idea what they might be. Her innovative approach to cognitive health incorporates concepts that most doctors have yet to learn. Busting through advice based on pseudoscience, Dr. Mosconi provides recommendations for a complete food plan, while calling out noteworthy surprises, including why that paleo diet you are following may not be ideal, why avoiding gluten may be a terrible mistake, and how simply getting enough water can dramatically improve alertness.
The evidence? Ritalin is FDA-approved to treat ADHD. It has also been shown to help patients with traumatic brain injury concentrate for longer periods, but does not improve memory in those patients, according to a 2016 meta-analysis of several trials. A study published in 2012 found that low doses of methylphenidate improved cognitive performance, including working memory, in healthy adult volunteers, but high doses impaired cognitive performance and a person’s ability to focus. (Since the brains of teens have been found to be more sensitive to the drug’s effect, it’s possible that methylphenidate in lower doses could have adverse effects on working memory and cognitive functions.)
Nootropics (/noʊ.əˈtrɒpɪks/ noh-ə-TROP-iks) (colloquial: smart drugs and cognitive enhancers) are drugs, supplements, and other substances that may improve cognitive function, particularly executive functions, memory, creativity, or motivation, in healthy individuals.[1] While many substances are purported to improve cognition, research is at a preliminary stage as of 2018, and the effects of the majority of these agents are not fully determined.