When I first started paleo, I went for a few months eating basically just meat and leafy greens. About a week in, I got a lot of thin vertical black lines on the ends of my fingernails. They eventually went away and never came back. I was feeling alot better after this dietary switch, so could it have been indicative of some healing process?
Wikipedia tells me these are called Splinter Hemorrhages and that "they could be due to hitting the nail ... a sign of inflammation in blood vessels all around the body ... or they could be where a bit of cholesterol has got lodged in the finger's capillaries."
Any ideas why this happened in my case? I imagine it has something to do with cholesterol being freed up from healing previously inflamed blood vessels.
By 'vertical,' I assume you mean they run lengthwise, in the same orientation as the finger itself. My understanding, that doesn't mean anything about your current condition, it just means you probably were in less than good health months ago when that portion of your fingernail first emerged from the cuticle. It's hard to diagnose back in time like that, so don't wrack your brain over it unless you've got a good hunch.
If the bands run widthwise across the finger, then it's something the doctor wants to see, maybe. But that would probably show up right at the cuticle, and it can be good news as well as bad.