Does Slippery Elm Affect Absorption of Vitamins?

Could you please tell me if slippery elm affects absorption of vitamins? My mother-in-law has taken this herb and she likes the results but is concerned it may alter or prevent vitamin intake.

Slippery elm bark powder, produced from the inner bark of the tree, is high in mucilage and tannins. The mucilage provides a soothing coating to the intestinal tract lining, while the tannins astringe (or tighten up) this mucous membrane lining. These actions are useful in diarrhea and other conditions of inflammation or sensitivity of the digestive tract.
All astringent (tannin containing) herbs inhibit absorption through the intestinal tract, so should be taken at separate times from vitamin and mineral supplements.
The most useful time to take slippery elm bark powder is at before bedtime, so that the digestive tract can be protected from the attack of acids for the entire night.
Other commonly used herbs that are high in tannins include mullein, red raspberry leaf, yarrow, St. John's wort, plantain and sage.