From the Research
A longer anagen phase is directly correlated with longer hair, as it allows for a prolonged period of active hair growth. The anagen phase is the active growth period of the hair follicle, during which hair cells divide rapidly and add to the hair shaft. In humans, the anagen phase for scalp hair typically lasts between 2-7 years, which is why scalp hair can grow quite long compared to hair in other body regions, as noted in a study published in the Journal of clinical medicine 1. For example, eyebrow or eyelash follicles have much shorter anagen phases (about 30-45 days), resulting in naturally shorter maximum lengths.
Some key factors that influence the length of the anagen phase include:
- Genetics, which primarily determines the duration of the anagen phase, as explained in a study on hair development published in Advances in experimental medicine and biology 2
- Hormonal factors
- Nutrition, with adequate protein, vitamins (especially biotin and vitamin D), and minerals like iron and zinc supporting optimal hair growth during this phase
- Age
- Certain medications, which can influence the length of the anagen phase, as discussed in a study on the hair growth effect of minoxidil published in Nihon yakurigaku zasshi. Folia pharmacologica Japonica 3
Conversely, factors that prematurely push hair follicles into the catagen (transition) or telogen (resting) phases, such as stress, certain medications, or health conditions, can effectively shorten the anagen phase and limit maximum hair length, as highlighted in a review on the hair cycle and hair loss published in the Journal of clinical medicine 1. Maintaining good nutrition and avoiding factors that disrupt the anagen phase can support optimal hair growth and lead to longer hair.