I'm yet to start the NSD and currently preparing for it, but today have encountered exactly the same query as you Davinci.
I've iodine tested three brands of supplements - Holland & Barrett turned dark black, but more worringly Nature's Own and Solgar turned dark brown (although they both claim to be "starch free"). However, I'm reassured if you say you've experienced no problems with Solgar Tim.
I also tested some apples which turned grey-brown, including an organic one (but to a lesser extent).
I'm very new to all this so don't know if I'm being overly cautious or not...
Martin
