My fingernails and toenails are much harder since I have been taking iodine.
I have to cut and shape them to keep them from getting to long. They used to just break. I have been putting colorless Iodine on them for a while now, (I don't remember when I started)
Someone on this forum had posted that it was a benefit to nails, so I just put a bottle of colorless Iodine next to my computer and put it on when I remember.