Why does my hair grow so fast?

I am 17. and my hair grows relatively fast. when i get a haircut at the same time as my friend, i have a shag in no time...while his hair remains short. why is this? am i eating more healthy than him? or just consuming more of a certain type of vitamin? i guess a better question is: what factors determine the speed of hair growth?

Why does my hair grow so fast?

heredity, weather (hair grows faster in summer than winter), the amount of keratin in your body, a diet rich in Vitamins A, B-Complex, C, D, E and iron, calcium will make hair and nails grow faster and healthier. Many factors.

Why does my hair grow so fast?

Family Genetics might have something to do with it.

Why does my hair grow so fast?

I am assuming you are a male. If so, the answer is testorone! At 17, your hormones are flaring.