Actually several such studies have been conducted. From what I've observed, it been mainly with fat soluble nutrients like vit A/D/E, etc.
*Sigh*
You still seem to be unable to distinguish between "vitamins", and other "nutrients". As I said, "vitamins" are those compounds necessary for an organism to maintain homeostasis and survive. I get the vast majority of my dietary vitamins and minerals from natural sources(ie food), however I do take a multi to 'fill in the gaps', so to speak. The other compounds in my "stack" are things like phytonutrients, which aren't 'necessary' per se, however they have shown to be extremely beneficial to human health.
I never said my supplement/diet regime is most ideal one there is. Plenty of factors are involved, such as genetic history, gender, etc. However I
am saying that at the moment, this is the optimal diet/supplement plan for me.
I do agree though that we've cluttered this thread enough. I've said what I felt is necessary so I will kindly leave.