At the time that I had my k pouch done (in 1979) I was told that if you can gain weight then you are absorbing enough.
In the long-term, I realized that that was not necessarily true. Yes, I absorb most things (especially those darned calories!) but some things need help.
I take my B vitamins in sublingual drops or dissolvable tablets (getting a shipment shortly from N.A.) and although I tried the Forvia Iron, I had a horrific allergic reaction to it and had to stop.
Now I take iron pills with orange juice (it helps to absorb the iron), a lot of trace minerals that can get lost in translation so I take mineral supplements (usually chewables) and calcium +D.
For the rest, I have tricks. I steam a lot of vegetables and do not throw out the water. I drink it like a tea. It contains a lot of trace minerals.
I mix and blend lots of fruits as smoothies (do not know if you can stand raw fruits, not everyone can) and make a vegetable soup every week with lots of green veggies (zucchini, green beans, celery, onions, garlic, a carrot for luck, an occasional tomato if it has nothing better to do, lots of fresh herbs and spices)...I flash cook it all in a pressure cooker then blend it and have it every day for lunch.
The result is that most of my numbers are pretty good. That said, if you suffer from chronic pouchitis, things are going through you faster than a freight train and may not stick around long enough to get absorbed.
My GP checks my numbers regularly. Depending on the season and what I am doing or eating they will change but over the years, I have learned to eat for my pouch and for my health.
Find what works for you and stick to it...
That is the trick
Sharon