Explain the Bioavailability of Thiamin?

Thiamin is readily available from the gut from food sources (as thiamin phosphate esters). Drugs and alcohol abuse may interfere with thiamin absorption and impair thiamin availability. Compared with most other vitamins, thiamin deficiency is seen more rapidly when low intake is encountered. Since thiamin is lost in cooking and is depleted by use of coffee, tannin from black teas, nicotine and alcohol, it is necessary to insure that intake of thiamin is optimal.