How long after a person stops taking a multivitamin might he get a vitamin deficiency in the u.s.?

Never: Good, healthy, as much as possible organic diet. Keeping good digestive system(healthy bowel flora- plain yogurt, keffir, ..), regular bowel movements. We absorb the vitamins from our food as long as we have good digestive system. Antacids, very popular recently, are interfering with digestion and therefore absorption, creating gass, etc., healthy flora produces multiple vitamins that we absorb.