[eurasiantiger]

Multivitamins are often sort of a scam: they contain cheap versions of vitamins that are not directly bioavailable, and essential minerals that are in a non-water-soluble form. All this leads to poor bioavailability.

In addition, some vitamin forms are actively harmful, such as the very common vitamin B12 form, cyanocobalamin, which releases cyanide as it becomes bioavailable. Better B12 forms such as methylcobalamin can be demethylated enzymatically and the free cobalamin is then able to bind to free cyanide (or other toxins) and remove them from the body.