What happens after the malabsorption is gone?

Different segments of a "normal" person's gastrointestinal tract absorbs different nutrients and vitamins.  The Duodenum which is at the exit of the stomach and is totally bypassed in RNY normally absorbs calcium, iron, and some water soluble vitamins.  The next segment of intestine is the Jejunum which part of is also bypassed with RNY and normally absorbs some water soluble vitamins, fats and carbs.  The next part of the intestine is called the Ileum which is not bypassed and will over time (about 18 months) take on the caloric absorptive powers of the Jejunum.  However, the Ileum cannot take on the full absorptive powers for vitamins and minerals that the Duodenum and Jejunum can. 

The result is that we must take 200% RDA of vitamins and minerals for the remainder of our lives to overcome vitamin and mineral malabsorption to stay healthy.  But, the caloric malabsorption is negated by the Ileum after about 18 months post-op RNY.

HTH, Mike