Biotin and hair color?

I've been taking Biotin for my nails - for year and a half, I believe. I suddenly realized that my "Biotin hair" is much, much darker than a "pre-Biotin" ends. New growth is almost jet black; it's also coarse. Old ends look completely different, both in texture and color (kinda dark chestnut). New growth looks exactly like my hair looked 15 years ago! How cool is that?

I've been also taking Glucosamine for my knee pain, and somehow I think my hair improvement is related to this as well.
Brunette, almost BSL length, growing out.
CG since Feb 2008, modified CG since September 2008.

I now know my texture/porosity!! (TY, Tiffany!) Medium texture; ends on a porous side; new growth - normal porosity.

Wash: Suave; EO Sweet Orange shampoo

Conditioner: GVP Balm, Mango Lustrasilk

Styling: KCCC, BRHG and LA Looks

Want to try: CJ