So I'm no professional, but my experience with dry and damaged hair has taught me a little. I have always had fairly thick wavy hair, until I put two weaves in it last December. BAD IDEA. TURN AROUND. DO NOT PASS GO. DO NOT COLLECT $100. Yeah, so you get the idea. As much as I loved having long hair (it flowed over my boobs quite nicely!), the extensions ruined it for months. When my friend and hair dresser cut them out, she couldn't believe how thin it had gotten. It was falling out in clumps and I was worried I'd wake up bald. So I took hair, skin and nails vitamins and got regular trims. But it was still falling out (but not as much).
So I started adding extra virgin coconut oil and coconut milk to my diet. I'd coat my hair in coconut oil and leave it in for a few hours, massaging it every half hour or so. The properties in coconut oil really made a difference to my hair, it was shinier and got so much healthier in a short amount of time. Yay! And now recently I've been reading about the benefits of B vitamins - healthy hair, skin and nails! So I've started taking a multi with B in it, and so now, almost 11 months after getting my extensions, it has come back to normal!
Be careful with coconut oil though, it's very good for you (or so I've read/experienced) but it is high in saturated fats, so in moderation, yeah?