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Although many people are concerned about their hair, not much is known about how hair works. For example
How long is a healthy hair cycle?
How many centimeters does hair grow in a year?
How many strands of hair does an adult person have?
What are the main components of hair?
What are the main components of hair?
In this second column, we would like to talk about hair from the viewpoint of science, from interesting knowledge that is beneficial to know to things that are surprisingly unknown.
Growth phase → regression phase → resting phase hair cycle
Hair has a cycle called the “hair cycle,” in which new hair grows back while repeating (1) the growth phase, (2) the regression phase, and (3) the resting phase.
(1) Growth phase
This is the period during which hair matrix cells repeatedly divide and hair grows thicker. It lasts 3 to 6 years for men and 4 to 8 years for women.
(2) Regression phase
The hair follicles begin to degenerate, and the rate of proliferation of hair matrix cells that used to make hair grow slows down rapidly.
(3) Quiescent phase
The resting phase lasts 3 to 6 months, during which time hair completely stops growing.
The above cycle is roughly 3 to 8 years for healthy hair, although there are some differences depending on gender, individual differences, and differences in care.
Hair grows 1 cm per month.
The standard for Japanese is 0.3 to 0.4 mm of growth per day, and on average, hair grows 1 mm in 3 days, 1 cm in 1 month, and 12 cm in 1 year. However, hair growth is not uniform and varies considerably from person to person. One of the factors that determine the speed of hair growth is a protein called growth factor, but it is not yet clear what kind of growth factor affects the speed. If we can identify it, we will be able to create a powerful hair growth product.
Approximately 100,000 hairs
The number of hairs in an adult Japanese person is said to be around 100,000. However, when looking through a scope, it is possible to see two or three hairs growing out of one pore, or only one. Also, the number of pores is fixed at birth and cannot be increased after birth. If a person’s hair looks fuller, it is because they have firm, thick hair and the amount of hair is that much larger. Conversely, if the number of hairs is large but only fine, the amount of hair will be small.
99% of hair is protein
99% of hair is composed of a protein called keratin. The amino acid methionine, which makes up keratin, is not synthesized in the body, so protein must be consumed daily in the form of soy, flour, milk, liver, eggs, meat, and fish. Malnutrition caused by excessive dieting can lead to hair loss and other hair problems because of protein deficiency.
