The sodium-dependent multivitamin transporter transports biotin, pantothenic acid and lipoate (Prasad et al. 1997). The three vitamins competitively inhibit transport of each other. Lipoate inhibits the transport of biotin and pantothenic acid (Prasad et al. 1998). Biotin is taken in microgram quanties while lipoic acid is taken in 600 milligram and higher quantites. What is more lipoate is synthesized on proteins whereby there is no need for free lipoic acid. All supplemental lipoic acid would be doing is blocking the transport of biotin and pantothenic acid.
Increasing levels of free antioxidants via supplmentation could be much worse than useless. Before iron can be absorbed iron must be reduced from Fe3+ to Fe2+. Antioxidants like vitamin C, vitamin E , beta-carotene and quercetin could one way or other promote the reduction of Fe3+ to Fe2+ in the gastrointestinal tract which would increase absorption. The goal, however, is to delay iron absorption as long as feasible.
There is oxidant stress in lots of illnesses but this could be due to dysregulation of selenoproteins and dysregulation of iron metabolism which would not be fixed by increasing levels of free antioxidants with supplemental vitamin C, vitamin E , beta-carotene, quercetin etc.
Supplementing with free antioxidants could be associated with very subtle but serious mineral dysregulations which would basically be undiagnosable.