Essential amino acids are the ones which have to be included in the diet. Keratin is a protein which is a building block of the hair and if one has a diet rich in proteins then it ensures that the hair repairs itself when it grows
Sources of good quality protein are milk, cheese and cereals, dairy products, soy, nuts, grains and seeds. Eating plenty of proteins ensure that the hair follicles continue to produce new hair.
Difficiency of protin can cause hair loss and brittle hair