For hair and nail growth I’ve always heard lots of protein helps. Have no idea if that is established fact, though.
Lasciel, you say “we” study this. Are you a forensic pathologist (I think that’s what it is called)?
Of course not! That’s the royal “we.” 
I kid - I meant “we” as in scientists in general.
I’m a librarian by profession, and a very active “armchair researcher.” 
Yes it is forensic pathology, and it’s a pretty damn cool area of study. For instance, there was a really interesting discovery in the last year or two that turned the field of cadaver decay study on its head - tests with vultures and other carrion birds revealed that the earlier methods of determining a time of death from the condition of bones and remnants could be months and even years in error, depending on whether the birds got to the body or it was recycled primarily by smaller animals, insects, and bacteria.
In other words, if you found a bleached human skellie in the woods, in one area of woods (no vultures) it would have to be many many decades old. In another (with vultures) it could be from someone who died only *months *ago. Now the forensics people know to check with the park rangers and naturalists to see if that specific location harbors carrion birds, before announcing the time of death. I find stuff like that to be fascinating.
Zsofia, I don’t know if you’re still interested in faster hair growth, but you might want to reconsider how you cleanse your hair. You might want to try CO (conditioner only) washing. Many shampoos have harsh detergents (sodium lauryl sulfates, etc) that are harsh and drying. A couple of years ago, I started washing my hair with Suave and Tresemme conditioners from the drugstore and I’ve since gotten rid of any shampoos. My hair is shiny, split end free, and clean. I don’t have “crispy” areas of my hair and my hairstylist remarks on the improved condition of my hair and scalp. Research CO washing on the web and you might be surprised.
Well, I already done got married with the hair I managed to grow at the time. It was fine. 
I do, actually, CO wash maybe three days out of four. My hair’s too fine to do it all the time - it gets kind of greasy looking without shampoo ever.