Different people experience different rate of hair growth. Also, hair growth depends on number of factors. Not only different rate of hair growth is seen in different individuals but an individual can experience different rates at different places around his head. Each and every hair follicle act differently and thus there is difference in hair growth.
Factors responsible for hair growth:-
1) Hormonal balance-
Hormones like cortisol, estrogen and thyroid should be in normal range. Increase in cortisol level which usually is seen during stress and decrease in cortisol level which occurs after stress both affect metabolism and hair growth. Adequate thyroid level ensures good metabolism resulting in good hair growth. On the other hand, increased level of estrogen can cause hair loss.
Eating a well balanced nutritious healthy diet is essential for good hair growth. You cannot feed your body all the unwanted unhealthy foods and drinks and expect it to remain healthy. If body is healthy, only then hair can remain healthy. Hair is made up of keratin which is usually protein. It also needs a lot of vitamins and minerals for healthy growth and individual who eat lots of raw fruits and vegetables experience healthy hair.
3) Good digestion-
Our digestive system should be efficient in digesting and metabolizing all the nutrients that we feed it. If it is not strong enough then it can hardly do its work well. For example, stomach acid which is hydrochloric acid should be in adequate amount which will ensure assimilation of protein which in turn will ensure healthy hair growth. In absence of adequate hydrochloric acid, protein assimilation does not take place.
4) Scalp health-
Scalp holds all the roots of hair in their follicles. Thus, healthy scalp which is free from dandruff and which is neither too dry nor too oily can promote better hair health and more growth in hair when compared to flaky, itchy scalp or the one which is excessively oily.
Your hair is growing faster than those of your friends. Reasons may be either that your diet is good, you are keeping your hair and scalp very clean and healthy or your hormonal levels are in adequate ranges. Either one or all the factors may be in your favor which are in turn favoring your hair growth. Your friends are suffering from hair loss or going towards baldness and the reason may be any of the factors mentioned above are compromised in their case and are not compromised in your case.
Since you are having good hair growth, it definitely does not mean that your dead cells are dying faster than others. Also, faster hair growth is not dependent on life expectancy of a person. Yes, hair and nails are dead cells of our body. Roots of hair are present beneath the skin and in case of hair on head, roots are present beneath the scalp. Hair begins in the root. Cells band together in the root to form a protein known as keratin. Follicle is located in skin and scalp and carries root of hair. Once hair grows in length, it gets pushed from root outside the follicle. Until hair is in follicle, it is supplied by tiny blood vessel. Once it gets pushed from follicle, it becomes dead because cells of hair strand are not alive. This is the reason that when hair cut is done one does not experience any pain but when same hair is pulled out from its root, it causes pain because root was still intact and alive in scalp within follicle.