To continue our nootropics journey we have more "natural" stuff - but all you junkies don't worry, we'll run out of natural things soon enough, and will have to dive into "synthetic" stuff :) And yeah, some vitamin supplements we take are man-made - but 100% modeled after the real deal. There are a couple of Vitamins that are interesting from life hacking perspective including Vitamin B and D complexes and vitamin E.
Vitamin D is important because if it's lacking - you may develop depression. It's also important for proper bone formation. So it's not that taking more than "usual" Vitamin D can improve your mental or bone health - but having too little can degrade your mood and weaken your bones. Researchers are also beginning to link vitamin D to cancer suppression but further research is needed to draw valid conclusions.
Similar to Vitamin B that most of us know is actually a vitamin complex - it's a group of chemicals including D1, D2, D3, D4 and D5 of which D2 (ergocalciferol) and D3 (cholecalciferol) are psychophysical relevant to humans. When only vitamin D is mentioned (without subscription) - it's usually referring to both D2 and D3.
Vitamin D3 is produced in the skin on exposure to ultraviolet B (UVB) light - either from sun or artificial source. That's why daily exposure to sunlight is important. But note that excessive exposure is not recommended, first because too much of it is linked to skin cancer - and second because after about 15 to 20 minutes (for light skinned individuals, or 3 to 6 times more is needed for pigmented skin) your skin produced all the D3 it can. After that any further D3 vitamin that's produced is degraded soon after.
It is also found in a small range of foods including: fatty fish (Catfish, Salmon, Mackerel, Sardines, Tuna, Eel), whole egg, beef liver and the only vegan source are mushrooms - and only after they have been exposed to UVB (sunlight or artificial) exposure.
Many (produced) foods such as milk, yogurt, margarine, cereals, bread and similar - are fortified with vitamins D2 and/or D3.
Then there's the Vitamin B we all think to know. It was once thought to be a single vitamin, like Vitamin A or C - but scientist latter discovered that there are several chemically distinct vitamins that usually coexist in the same foods. When someone mentions Vitamin B complex - such as in case of supplements - they are referring to the eight B vitamins: B1, B2, B3, B5, B6, B7, B9 and B12.
The "gaps" (B4, B8 ...etc.) are missing because they initially placed some chemicals/compounds under those names - latter to discover those shouldn't be placed there :)
From nootropic and life hacking point of view, B Vitamins are interesting because of their effect in cognitive function - in particular scientific studies have been able to link brain function improvements to B1, B9 and B12. While not all B vitamins play a role in improving brain function, others help in the synthesis of chemicals or other body functions - and we cover them all here since the lack of some can seriously impair your psychophysical performance and health.