Quote from ByLoSellHi:
I don't believe so, DC.
Most vitamins one takes orally are excreted, intact, in the urine. There was a massive Lancet study that showed over 98% of orally taken vitamins passed through the urine, unabsorbed.
There are some that do get absorbed through the gut or GI tract, but they are few in number, and tend to be the 'fat seeking' or lipophilic type, such as Omega-3 fatty acids from cod, sardine, mackerel or other fish species - the better quality supplements here are run through processes that allow the manufacturer to suspend and discard the toxins that accumulated in the fish.
Subcutaneous injections of certain vitamins and supplements is the best way to get absorption, as this method bypasses the gut and GI tract, altogether. But quite a few vitamins can't be administered this way.