Substances that remain stuck in the body

[Superfluo]

Hi!

I've bought a B-complex supplement and among the ingredients there's an ingredient called Povidone K90. Searching online I've found that povidone is harmless. If it has small molecular weight it is excreted with urine, but if it has a big molecular weight, like the K90 type, it can go in the kidneys or in other parts of the body and it won't be excreted with urine.

My question concerns this substance but extends to all harmless substances that are not excreted. Are they truly harmless? I am a bit concerned with their safety, because our body is not built to have these substances inside. But they are deemed safe.

[Superfluo]

Bump.