Plant tannins are increasingly being recommended to deal with medical issues, as a natural remedy recommended by homeopathic doctors and practitioners.
Iron absorption and plant tannins - In short, not an issues with Tanalbit. Apparently plant tannins (not condensed tannins, like in Tanalbit) can prevent absorption of iron (specifically non-meat based iron), since they are part of a plant's natural defense against being eaten, as they disrupt digestion from herbivores. Condensed tannins (or Proanthocyanidins) do not inhibit iron absorption. There is a similar claim about plant tannins causing cancer, but again that's the difference between hydrolysed vs condensed tannins.
Food sources of condensed tannins / proanthocyanidins: grapes (seeds and skins), apples, unsweetened baking chocolate, red wines, blueberries, cranberries, bilberries, black currants, hazelnuts, pecans, pistachios. The highest concentrations of proanthocyanidins in fruits known to date were detected in black chokeberries. Or you can take a supplement like Tanalbit.
Klebsiella pneumoniae - Plant tannins were identified (through laboratory analysis of my fecal test, CDSA 2.0 if you are interested in taking the test) as an effective non-prescriptive natural way to deal with my overgrowth of a specific pathogen in my gut (klebsiella pneumoniae). The test results identified the 5 effective prescriptions and the 1 prescription to which that pathogen is apparently resistant, and also listed four natural agents and how effective each would be against that specific pathogen in gut - among the natural agents, plant tannins had the best effect on that pathogen (note that I'm not saying that it would be best for that pathogen in anyone's gut, as it could be a different strain that someone else had!).
Ulcerative colitis - According to an article in the Natural Medicine Journal, the use of condensed tannins for treatment of ulcerative colitis is both safe and effective. "Oral consumption of condensed tannins can be assumed to be safe in humans, but it would stand to reason that due to the proanthocyanidins' ability to bind metals and proteins, they would be most effective and beneficial to ingest separately from food and other medications. A diet rich in tannin-containing foods might aid in the prevention of UC progression and help maintain remission in patients with UC. Several commercial products exist with high tannin content, and these should be further investigated in the treatment of UC." [Catherine Clinton, ND; Plant tannins: A novel approach to the treatment of ulcerative colitis]
Yeast/Candida - Apparently candida/yeast overgrowth can be managed through condensed tannins (or oregano oil caps).
So 3 things that condensed tannins may help with. This is mostly to help you in your own research, hope it helps!